Pest Management Guidelines - Home
Pest Management Guidelines
A Cornell Cooperative Extension Publication

  
New York Pest Management Guidelines

Home | CALS | PMEP | All IPM Guidelines




Tree and Shrub Pest Mangement

10. Tree and Shrub Pest Management

 

Contents

Growing Degree Days

Key Plants and Key Pests

Sample IPM Program: for Gypsy Moth

Further Reading

Table 10. Key tree and shrub pests: Management by month

Table 11. Pest management for woody ornamentals (trees, shrubs, and vines)

Andromeda

Arborvitae

Azalea

Birch

Boxelder

Boxwood

Clematis

Cotoneaster

Crabapple

Dogwood

Douglas-fir

Dutchman’s pipe

Elm

Euonymus

Firethorn

Flowering peach, cherry, and plum

Hawthorn

Hemlock

Holly

Honeylocust

Honeysuckle

Horsechestnut and Buckeye

Hydrangea

Ivy (Boston)

Ivy (English)

Juniper

Lilac

Linden (littleleaf)

London plane and Sycamore

Magnolia

Maple

Mountain ash

Mountain laurel

Oak

Pachysandra

Pieris

Pine

Privet

Pyracantha

Quince

Rhododendron

Rose

Spruce

Sycamore

Taxus

Viburnum

Willow

Yew

 

 

Pesticides are one option in a pest management program. Home gardeners must first decide whether control is needed when a problem arises and then decide if pesticides are the proper choice for their situation. See Chapter 9 in Part I: Cultural Methods, of Pest Management Around the Home, for non-pesticide management methods.

Table 11 lists pesticide options for commonly encountered pests and diseases of woody ornamentals, including trees, shrubs, vines, and woody groundcover plants. For toxicity information, see Table 3 in Chapter 3 and Tables 4b and 4c in Chapter 4. Trees or shrubs that are grown for edible fruits are discussed in Chapters 11 and 12 since often the pesticides that may be used on fruit plants differ from those that may be used on ornamental woody plants.

When a treatment is listed for application during the “dormant” stage, this is the period just before budbreak. At this time, insect activity is beginning to accelerate, there is no foliage canopy, and complete coverage is obtained. The dormant spray should be applied on a clear, calm day when temperatures are above 40° F. Key bud stages for flowering trees and shrubs are:

 

  • Dormant: just before buds begin to swell in spring.
  • Green tip: buds are open at tips and exposing green tissue.
  • Half-inch green: one-half inch of green tissue is projecting from bud.
  • Tight cluster: blossom buds are exposed but tightly appressed; stems are short.
  • Pink: all blossom buds are pink, stems are fully extended.
  • Bloom: from the time the blossoms first open until the petal-fall stage is reached.
  • Petal-fall: petals have fallen.

Some horticultural oils may be used during the dormant period and as “green,” “growing season,” or summer sprays. Others should only be applied at the dormant stage. Check the product label prior to purchase. Horticultural oils affect the eggs and immature stages of aphids, scales, plant bugs, psyllids, certain caterpillars, and mites. See Chapter 2 of this publication for additional information on horticultural oils, as well as information on insecticidal soap.

 

Growing Degree Days

As we learn more about the biology of insect pests, we will be able to make timely management decisions. More accurate timing will allow us to reduce the number of pesticide applications needed. A system using growing degree days (GDD), which are more accurate than calendar dates, is used to determine when to apply pesticides to ornamental trees and shrubs. The climatological calendar begins on March 1, and the base temperature is 50° F. The GDDs are additive, giving a cumulative total for each day of the growing season.

These formulas, in degrees Fahrenheit, are used to determine GDD for each day:

(Maximum + minimum daily temperature) divided by 2 = Mean Temperature

Mean temperature (in Fahrenheit) minus 50 = Growing Degree Days (GDD)

**Note that the GDD can never be negative; if the above calculation yields a negative number, the number of GDDs for that day is zero.

Insect development can be tied directly to GDD accumulations, especially in the spring, when most activity begins. Apply the pesticide when GDDs have reached the levels listed in the tables. Consult your county Cooperative Extension educator for local GDD data for pest management. Known GDD information is included in Table 11.

 

Key Plants and Key Pests

Knowing which pests are most common and cause the most damage can also be helpful. Arborists and landscape contractors who manage pest problems are faced with over 175 insect pests and 110 different diseases, but not every pest occurs every year in damaging numbers. One goal in an integrated pest management approach is to monitor the major pests of the most common and significant plants in each landscape.

Table 10, which lists key plants and key pests, may help in planning your annual inspection schedule. The pests are grouped according to the first months in which they should be managed or controlled. Certain pests, such as aphids and mites, may continue to be pests for many months.

 

Sample IPM Program: for Gypsy Moth

The gypsy moth, a forest and shade tree pest that can cause widespread defoliation, is an introduced insect that has few natural enemies in our country. Management options for homeowners include planting resistant species; improving plant health by watering and fertilizing properly; removing and destroying egg masses anytime from September through mid-April; assessing the population and potential damage when young larvae are present in late May or early June and treating if needed; using bands around trees to trap larger larvae or to prevent larvae from entering the canopy; and destroying pupae as found.

Gypsy moth traps are available, but they aren’t recommended as a control measure. They are very useful in monitoring the spread of gypsy moth into new areas, but they trap only male moths, which does not significantly reduce the overall population.

 

Further Reading

Compendium of Conifer Diseases. Hansen, E. M. and K. J. Lewis. 1997. American Phytopathological Society, St. Paul, Minn. 128 pp.

Compendium of Elm Diseases Stipes, R. J., and R. J. Campana. 1981.. American Phytopathological Society, St. Paul, Minn. 96 pp

Compendium of Rhododendron and Azalea Diseases Coyier, D. L., and M. K. Roan. 1986.. American Phytopathological Society, St. Paul, Minn. 65 pp.

Compendium of Rose Diseases and Pests, 2nd edition. Horst, R. K. and R. Cloyd. 2007. American Phytopathological Society, St. Paul, Minn. 96 pp.

The Cornell Guide to Planting and Maintaining Trees and Shrubs. George Good and R. K. Weir III. 2005. Cornell Cooperative Extension Info. Bulletin 24. Ithaca, NY. 25 pp.

Diagnosing Injury to Eastern Forest Trees. Skelly, J. M., and W. Merrill. 1987. Pennsylvania State University, University Park. 122 pp.

Diseases of Trees and Shrubs. Sinclair, W. A., H. H. Lyon, and W. T. Johnson. 1987. Cornell University Press, Ithaca, N.Y. 574 pp.

Insects That Feed on Trees and Shrubs. Johnson, W. T., and H. H. Lyon. 1988. Cornell University Press, Ithaca, N.Y. 556 pp.

Pruning: An Illustrated Guide to Pruning Ornamental Trees and Shrubs. Rev. ed. Rakow, D. A., and R. Weir III. 1993. Cornell Cooperative Extension Information Bulletin 23. Ithaca, N.Y. 28 pp.

Scouting and Controlling Woody Ornamental Diseases in Landscapes and Nurseries. Moorman, G. B. 1992. Pennsylvania State University, University Park. 90 pp.

Westcott’s Plant Disease Handbook. 5th ed. Horst, R. K., ed. 1990. Van Nostrand Reinhold, NY. 953 pp.

NYS IPM Interactive Plant Manager -- Diagnosing Pests of Woody Ornamental Plants: http://www.entomology.cornell.edu/public/IthacaCampus/ExtOutreach/DiagnosticLab.html

Cornell IPM Guidelines: http://ipmguidelines.org/treesandshrubs/

Cornell’s Plant Clinic (Plant Diseases): http://plantclinic.cornell.edu/

Cornell Gardening Web Site: http://www.gardening.cornell.edu/

 

 

Table 10. Key tree and shrub pests: Management by month

Ideal time to manage

Pest

Principal hosts

March (Dormant)

spider mite

evergreens, crabapple

 

elongate hemlock scale

hemlock

 

maple gall mite

maple

 

pine bark adelgid

white pine

 

eastern spruce gall adelgid

white and Norway spruces

 

tuliptree scale

Tuliptree, star magnolia

 

euonymous scale

pachysandra, euonymus

 

black knot

plum, flowering cherry

Early April

white pine weevil

white pine (main shoot), spruce, Douglas fir

Mid- to late April

tent caterpillar

cherry, crabapple

 

European pine sawfly

Mugo, scots, other pines

 

anthracnose

maple, ash, oak, linden, dogwood

 

hawthorn leaf spot

hawthorn

 

honeylocust plant bug

honeylocust

 

scab

apple, crabapple, hawthorn

 

juniper twig blight

juniper, cedar

 

Diplodia blight

pines (especially Austrian)

Early May

birch leafminer

birch

 

aphid

deciduous plants

 

dogwood borer

flowering dogwood

 

euonymous scale

euonymus, pachysandra

 

Cooley spruce gall adelgid

blue spruce

 

white pine aphid

white pine

 

cankerworm

oak, linden, beech, elm

 

pachysandra blight

pachysandra

 

viburnum leaf beetle

viburnum (esp. cranberry and arrowwood)

Mid- to late May

gypsy moth

oaks, maple, many trees

 

spruce spider mite

spruce, juniper, arborvitae

 

rhododendron borer

rhododendron

 

lacebug

sycamore, walnut

 

woolly beech aphid

beech

 

black vine weevil

rhododendron, azalea, yew

 

Verticillium wilt

maple

 

black spot, mildew

rose

Early June

lace bugs

andromeda

 

bronze birch borer

birch

 

elongate hemlock scale

hemlock

 

rose chafer

rose

 

spruce canker (Cytospora)

spruce, fir

 

Phytophthora wilt

rhododendron and azalea

Mid- to late June

bagworm

arborvitae, juniper

 

leafhopper

maples, deciduous plants

 

juniper scale

juniper

 

white prunicola scale

flowering cherry and plum

July

Japanese beetle

many deciduous plants

 

fall webworm

many deciduous plants

 

spider mite

evergreen and deciduous plants

 

 

Table 11 Notes:

* Disease Sanitation Practices: Avoid crowding plants; allow air to circulate around and within plants. Prune to thin plants or plantings and/or to remove diseased parts. Prune only when conditions are dry, and, where feasible, disinfect pruning tools between cuts or between plants. Discard all diseased tissue and in autumn, rake and discard or destroy all fallen leaves, fruit, and branches. Avoid wetting foliage overnight or for long periods of time.

** Imidacloprid: Products containing imidacloprid are not registered for use in certain New York City and Long Island counties (Kings, Queens, Nassau, and Suffolk). Most formulations of imidacloprid once available to homeowners are now classified as restricted-use (for professional application only) in New York State. Check product status and label prior to purchase.

 

Table 11. Pest management for woody ornamentals (trees, shrubs, and vines)

Also see Chapter 9 in Part I: Cultural Methods, of Pest Management Around the Home.

For large trees, consult a professional applicator.

Plant

Pest

Some Pest Management Options

Andromeda

(Pieris)

 

Lace bug
(Stephanitis spp.)

 

lace bug

Natural enemies are rarely abundant enough to control damaging populations. Infestations are more severe in sunny, exposed sites. If needed, treat in early to mid-May (120+ GDD). Spray undersurfaces of leaves. Use carbaryl, cyfluthrin, lambda-cyhalothrin, or insecticidal soap (potassium salts of fatty acids). Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Spider mites

When problem appears, use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, Mite-X (plant extracts), or neem oil. Treat undersides of leaves as well as upper sides. Repeat application may be necessary. Or use disulfoton, as a systemic insecticide.

Arborvitae

(Thuja)

Twig/Tip blight (Phomposis, Kabatina, Sirococcus, etc.)

Follow disease sanitation practices* (see note). Apply azoxystrobin (not near apples), or copper sulfate, following label directions.

 

Arborvitae leafminers

Remove and destroy infested leaves from fall until early spring. If needed, treat with acephate, lambda-cyhalothrin, or spinosad. For larvae, apply in mid-May (150–260 GDD) and early August (1800–2200 GDD). For the moth stage, treat in mid-June (533–700 GDD). Or use imidacloprid** (see note) as a systemic.

 

Arborvitae weevil

Apply neem oil.

 

Bagworm

Handpick and remove. If needed, use Bt (Bacillus thuringiensis ssp. kurstaki), carbaryl, cyfluthrin, lambda-cyhalothrin, malathion, or spinosad. Spray in early to mid-June (600–900 GDD).

 

Scales

To control crawlers, use acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or neem oil. Imidacloprid** (see note) can be used as a systemic.

 

Spider mites

 

spider mite

Use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Apply after new growth begins mid- to late May (192–363 GDD), and in late August through mid-September (2375–2806 GDD). Treat undersides of leaves as well as upper sides.

Azalea

(Also see Rhododendron)

Flower blight
(Ovulinia azaleae)

Follow disease sanitation practices* (see note). Apply chlorothalonil, myclobutanil, potassium bicarbonate, or propiconazole.

Phytophthora root rot

Use chlorothalonil especially before replanting site with new plants.

 

 

Phytophthora shoot blight

Follow disease sanitation practices* (see note). Apply chlorothalonil, or copper ammonium carbonate.

 

Azalea bark scale

Signs and symptoms include scales on bark, honeydew, sooty mold, leaf yellowing, and dieback.

As a dormant spray in April, horticultural oil may be applied. To control crawlers (the mobile stage of scale insects), in late June to late July, apply acephate, carbaryl, cyfluthrin, horticultural oil, insecticidal soap, lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** (see note) as a systemic.

Black vine weevil
larva (above) and pupa (below)

Black vine weevil

P48LARVAA

For adult weevils, remove by hand, use pitfall traps, or burlap collars. If needed, treat with acephate or lambda-cyhalothrin in early June and early to mid-July. Apply full coverage spray to foliage and the soil beneath plants.

To control the larvae, use entomophagous nematodes, or imidacloprid** (see note).

 

Lace bug

(Stephanitis spp.)

Infestations are more severe in sunny, exposed sites. If needed, use acephate, carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin. Spray the undersides of leaves. Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Sawfly

Apply acephate, carbaryl, imidacloprid**, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or spinosad. Check the pesticide label for proper growth stage for treatment. Some products are labeled only for larvae control.

 

Southern red mite

In mid-June (618–802 GDD), use insecticidal soap (potassium salts of fatty acids) or lambda-cyhalothrin.

 

Spider mites

If needed, use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Treat both upper and undersides of leaves. Or use disulfoton, as a systemic.

 

Whitefly

Large populations may require the use of insecticides. Treat in early June (448–700 GDD), mid-July, and mid-August (1250–1500 GDD). Apply to undersides of leaves. Use acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use a systemic applied to the soil in early spring: disulfoton, or imidacloprid**.

Birch

(Betula)

 

Aphids

If a problem, spray with acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, permethrin, or Mite-X (plant extracts). Or use imidacloprid** as a systemic.

 

Birch leafminer

P48LEAFB

The larvae make blotch mines on the leaves.

If a problem, apply two sprays: mid-May (190–290 GDD) and mid-June (530–700 GDD). Apply acephate, carbaryl, lambda-cyhalothrin, or permethrin. Or use imidacloprid** (see note) as a systemic.

 

Birch skeletonizer

Spray when insect is observed, beginning about the second week of July (1266–1580 GDD). Use spinosad.

 

Bronze birch borer

Borer damage causes dieback from the top of the tree downwards. Have trees treated by a certified applicator, or apply permethrin (check that label lists bronze birch borer) or imidacloprid**.

Boxelder

(Acer negundo)

Boxelder bug

boxelder

These plant bugs feed on developing seeds of boxelder and other maples (Acer species). One option is to remove seed-bearing trees. Or, when nymphs or adults are observed on the trees, apply carbaryl, cyfluthrin, or lambda-cyhalothrin.

Boxwood

(Buxus)

Boxwood leafminer

Remove infested leaves by hand. If needed, treat during early June (448–700 GDD), getting good coverage of the undersides of leaves. Apply acephate, carbaryl, or malathion. Or use imidacloprid** as a systemic.

 

Boxwood psyllid

To remove overwintering eggs, every few years prune tips of plants in winter or early spring before eggs hatch and destroy prunings. If needed, spray in late May before leaves become cupped (290–440 GDD). Apply carbaryl, horticultural oil, or insecticidal soap (potassium salts of fatty acids). Or use imidacloprid** as a systemic.

 

Boxwood mite

Bronze stippling on foliage is a sign of mite feeding damage. Treat in early May (245–600 GDD), including undersides of leaves as well as upper sides. Use insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or Mite-X (plant extracts).

Clematis

Leaf spot and stem rot (Ascochyta clematidina)

Follow disease sanitation practices* (see note). Apply potassium bicarbonate following product label directions.

 

Blister beetle

Handpick (wearing gloves) and destroy beetles. If needed, apply imidacloprid** or neem oil.

Cotoneaster

Fire blight

Prune out infected parts when plants are dry, making each cut several inches below areas of visible discoloration. Disinfect tools between cuts. If needed, apply Bacillus subtilis (for suppression).

 

Lace bug

Treat twice: mid-May (293–363 GDD) and mid-July (1266–1544 GDD). Spray undersides of leaves. Use acephate, carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin. Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Pearleaf blister mite

Dark blister-like blotches on leaves are a symptom of these mites. Spray carbaryl as leaves emerge in spring. Treat undersides of leaves as well as upper sides.

 

Pearslug

(sawfly larva)

If needed, apply acephate, carbaryl, imidacloprid**, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or spinosad.

 

Scales

Use acephate, cyfluthrin, horticultural oil, imidacloprid**, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil.

Crabapple

(Malus)

Cedar-apple/hawthorn rust

Remove any nearby junipers, if feasible or when sphere-shaped galls on nearby junipers produce orange masses (jellylike and sometimes stringy), treat crabapple trees with chlorothalonil, myclobutanil, potassium bicarbonate, propiconazole, or sulfur.

 

Powdery mildew

Follow disease sanitation practices* (see note). Apply Bacillus subtilis, chitosan, myclobutanil, potassium bicarbonate, propiconazole, or sulfur.

 

Scab

Follow disease sanitation practices* (see note). Apply Bacillus subtilis (for suppression), chlorothalonil, myclobutanil, potassium bicarbonate, propiconazole, or sulfur.

 

Aphids

Spray when observed, with cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Or use imidacloprid** as a systemic. (DO NOT USE imidacloprid if you plan to use fruit for cooking or eating).

 

Eastern tent caterpillar

The larvae make webs in branch crotches and chew the leaves. Remove by hand. Remove and destroy egg masses over winter. If needed, treat once in late April to early May (90–190 GDD), with Bt (Bacillus thuringiensis ssp. kurstaki), carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or spinosad.

 

 

Gypsy Moth

Remove and destroy egg masses over winter. If needed, spray foliage in May after larvae hatch (90–448 GDD). Use Bacillus thuringiensis ssp. kurstaki, lambda-cyhalothrin, or cyfluthrin, before larvae reach 1 inch in length. Or use carbaryl, or spinosad.

 

Japanese beetle

Japanese beetle

Handpick and remove beetles. Treat foliage when adults are observed and if needed, continue at weekly intervals until beetle season is over. Apply carbaryl, cyfluthrin, imidacloprid** (DO NOT USE imidacloprid if you plan to use fruit for cooking or eating), lambda-cyhalothrin, malathion, neem oil, pyrethrins plus PPB, or spinosad.

 

Leaftiers and rollers

Handpick and destroy, where possible. Begin treating by June 1st, with carbaryl, cyfluthrin, lambda-cyhalothrin, neem oil, or spinosad.

 

Roundheaded appletree borer

The adult beetles make exit holes in the bark near the tree base, after tunneling in the trunk as larvae. To prevent adults from laying eggs, ring the bottom 12–24 inches of the trunk with oviposition barriers in May. Use wire mosquito netting, hardware cloth, or several layers of newspapers. Barriers should be loose except at the bottom (cover with soil) and top (tie with cord). Remove barriers at the end of the season (October).

Remove adults by hand, if seen. Imidacloprid** may be used as a systemic (DO NOT USE imidacloprid if you plan to use fruit for cooking or eating).

 

Scales

If scale infestations are small, prune out affected plant parts. Horticultural oil may be applied at the dormant stage in April before new growth begins. For summer treatment when crawlers are active, use cyfluthrin, horticultural oil (summer or all-season type), insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** as a systemic (do not use if you plan to use fruit for cooking or eating).

Dogwood

(Cornus)

Anthracnose
(Discula destructiva)

Follow disease sanitation practices* (see note). Apply chlorothalonil, copper ammonium carbonate, myclobutanil, potassium bicarbonate, propiconazole, or sulfur.

 

Powdery mildew

Follow disease sanitation practices* (see note). Apply azoxystrobin (not near apples), Bacillus subtilis, copper ammonium carbonate, myclobutanil, or potassium bicarbonate.

 

Cottony maple scale, Cottony maple leaf scale

If scale infestations are small, prune out affected plant parts. Horticultural oil may be applied at the dormant stage, in April before new growth begins. For crawlers in June (802–1265 GDD), spray with cyfluthrin, horticultural oil (summer or all-season type), insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** as a systemic (DO NOT USE imidacloprid if you plan to use fruit for cooking or eating).

 

Dogwood borer

Prune to maintain vigor. If necessary, imidacloprid** may be used as a systemic (do not use if you plan to use fruit for cooking or eating).

 

European fruit lecanium scale

If scale infestations are small, prune out affected plant parts. There are many effective parasitic insects that help control the scale. If needed, use horticultural oil in mid-April to early May (35–145 GDD) for dormant treatment. In mid- to late July (1266–1645 GDD), treat for crawlers using cyfluthrin, a summer or all-season type horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** as a systemic. (DO NOT USE imidacloprid if you plan to use fruit for cooking or eating).

Douglas-fir

(Pseudotsuga)

Rhabdocline needlecast, and Swiss needlecast

Apply chlorothalonil, following label directions

 

Cooley spruce gall adelgid

Do not plant Douglas-fir near blue spruce as the adelgid uses both as hosts. Damage is rarely serious. If needed, treat in early May (120–190 GDD) and again in early August (1500–1775 GDD). Use carbaryl, horticultural oil, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin. Or use imidacloprid** as a systemic.

 

White pine weevil

Cut out and destroy wilted or dead leaders by the end of June. No pesticides are currently registered for homeowner use in New York State.

Dutchman’s pipe

(Aristolochia)

Mealybug

mealybug

Spray biweekly, mid-May through mid-June, with cyfluthrin, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or malathion. Or use imidacloprid** (see note) as a systemic.

 

Scales

Use cyfluthrin, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or neem oil. Or use imidacloprid** as a systemic.

Elm

(Ulmus)

Elm leaf beetle

Natural enemies are generally not abundant enough to provide control. In late May or early June (363-530 GDD), treat with cyfluthrin, lambda-cyhalothrin, permethrin, or spinosad. Or use imidacloprid** as a systemic.

Euonymus

 

Crown gall

Inspect new transplants carefully before adding to the landscape; no pesticides are currently available for home use.

 

Euonymus caterpillar

Remove by hand (wear gloves). If needed, use spinosad.

 

Euonymus scale

 

P51LEAVESA

Symptoms of this scale include yellow spots on leaves and gray-white scurfy material on stems. Where possible, prune out scale-infested branches. Resistant euonymus species are recommended for future plantings.

Horticultural oil may be applied as a dormant spray, in mid-April to early May (35–120 GDD). To control crawlers, treat in early to mid-June (533–820 GDD) and again in mid-July (1150–1388 GDD). Use a summer or all-season type horticultural oil, acephate, cyfluthrin, lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** (see note) as a systemic.

Firethorn

(Pyracantha)

Fire blight

Prune out infected parts when plants are dry, making each cut several inches below areas of visible discoloration. Disinfect tools between cuts. Apply Bacillus subtilis (for suppression).

 

Scab

(Venturia pyracantha)

Follow disease sanitation practices* (see note). If the disease has been severe, apply Bacillus subtilis (for suppression), chlorothalonil, or potassium bicarbonate.

 

Lace bug

Treat twice, in mid-May (239–363 GDD) and in mid-July (1266–1544 GDD). Spray undersides of leaves, using acephate, carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin. Or use imidacloprid** (see note) as a systemic.

 

Scale

During the dormant stage, use horticultural oil. Treat crawlers in summer with acephate, cyfluthrin, horticultural oil (all-season or summer type), insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** as a systemic.

Flowering peach, cherry, and plum

(Prunus)

 

For trees used for edible fruits, see Chapter 11:

Tree Fruit Pest Management.

 

Do not use a systemic insecticide such as acephate or imidacloprid, if fruits will be used for cooking or eating.

Black knot

No pesticides are currently available. Follow disease sanitation practices* (see note) In winter, prune old knotted twigs and bury or burn. Destroy wild trees with knots along nearby hedgerows.

Cherry leaf spot

Follow disease sanitation practices* (see note) In autumn, remove and destroy fallen leaves, fruits, and dead twigs. Apply copper sulfate or propiconazole, if needed.

Monilinia shoot blight

Follow disease sanitation practices*. When blossoms open and again 10 days later, apply chlorothalonil or potassium bicarbonate.

Aphids

Spray when observed, using acephate, cyfluthrin, (may not be effective for green peach aphid), horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Or use imidacloprid** as a systemic.

Borers

The adult beetles make exit holes in the bark near the tree base, after tunneling in the trunk as larvae. To prevent adults from laying eggs, ring the bottom 12–24 inches of the trunk with oviposition barriers in May. Use wire mosquito netting, hardware cloth, or several layers of newspapers. Barriers should be loose except at the bottom (cover with soil) and top (tie with cord). Remove barriers at the end of the season (October).

Permethrin may be used if the product label lists borers on that kind of tree. Or use imidacloprid** as a systemic.

 

Eastern tent caterpillar

The larvae make webs in branch crotches, and chew the leaves. Remove by hand. Remove and destroy egg masses in winter. If needed, treat once in late April to early May (90–190 GDD), with acephate, Bt (Bacillus thuringiensis ssp. kurstaki), carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, permethrin, or spinosad.

 

European fruit lecanium scale

As a dormant spray in mid- to late April (35–145 GDD), apply horticultural oil. In mid-July (1266–1645 GDD) treat for crawlers with acephate, cyfluthrin, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Japanese beetle

Remove by hand, where possible. Spray when observed and continue at weekly intervals, if needed. Use acephate, carbaryl, cyfluthrin, lambda-cyhalothrin, malathion, neem oil, pyrethrins plus PPB, or spinosad. Or use imidacloprid** as a systemic.

 

Spider mites

Horticultural oil may be applied in April (7–121 GDD) before new growth begins. After new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Treat undersides of leaves as well as upper sides.

 

White prunicola scale

Signs and symptoms include a white coating on trunk and twigs, and dieback. Prune out where possible. Rather than applying pesticides, commercial applicators may powerwash the trunk to remove scales. Horticultural oil may be used as a dormant spray in April (35–145 GDD). Treat for crawlers in mid-June to early July (707–1151 GDD), using acephate, cyfluthrin, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or neem oil. Or use imidacloprid** as a systemic.

Hawthorn

(Crataegus)

Cedar-apple/cedar-hawthorn rust

Remove any nearby junipers, if feasible. When sphere-shaped galls on nearby junipers produce orange masses (jellylike and sometimes stringy), treat hawthorn with chlorothalonil, copper ammonium carbonate, myclobutanil, potassium bicarbonate, or propiconazole.

 

Diplocarpon (Entomosporium, Fabreae) leaf spot

Follow disease sanitation practices* (see note). Plant only native hawthorns. Apply chlorothalonil or copper sulfate if needed.

 

Fire blight

Prune out infected parts when plants are dry, making each cut several inches below areas of visible discoloration. Disinfect tools between cuts. Apply Bacillus subtilis (for suppression).

 

Roundheaded appletree borer

The adult beetles make exit holes in the bark near the tree base, after tunneling in the trunk as larvae. To prevent adults from laying eggs, ring the bottom 12–24 inches of the trunk with oviposition barriers in May. Use wire mosquito netting, hardware cloth, or several layers of newspapers. Barriers should be loose except at the bottom (cover with soil) and top (tie with cord). Remove barriers at the end of the season (October). Imidacloprid** may be used as a systemic.

 

Lace bug

Treat foliage, especially undersides of leaves, in mid-May (239–363 GDD) and again in mid-July (1266–1544 GDD). Use acephate, carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin. Or use imidacloprid** as a systemic.

 

Leafminer

Spray twice, the first and third week of June, with acephate or lambda-cyhalothrin. Or use imidacloprid** as a systemic.

 

Scales

Treat for scale crawlers with acephate, cyfluthrin, horticultural oil, imidacloprid**, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or neem oil.

 

Spider mites

Horticultural oil may be applied at the dormant stage, in April (7–121 GDD) before new growth begins. After new growth begins mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Treat undersides of leaves as well as upper sides.

Hemlock

(Tsuga)

Elongate hemlock (Fiorinia) scale

Avoid nitrogen fertilization. Scale symptoms include yellow needles and premature needle drop (note that some drop each year is normal, of needles that are a few years old). Horticultural oil may be applied as a dormant spray in early April (7-120 GDD). In early June (360–700 GDD), treat for crawlers with acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Hemlock rust mite (eriophyid mite)

In early April (7–22 GDD), apply a horticultural oil labeled for mites.

 

Hemlock scale

Avoid nitrogen fertilization. Scale symptoms include yellow needles and premature needle drop. Parasites often keep this scale under control. Horticultural oil may be applied as a dormant spray in April (35–121 GDD). In mid-July to mid-August (1388–2154 GDD) treat for crawlers with acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Hemlock woolly adelgid

Signs and symptoms include cottony white egg sacs along branches, needle yellowing, and dieback. Western hemlocks appear to be resistant. Do not apply nitrogen fertilizer to infested hemlocks, as it promotes adelgid growth. At the dormant stage (late April to early May), apply horticultural oil. In late June or late September and the following year in early June, treat with insecticidal soap. Thorough coverage with oil or soap is necessary. Hire certified applicators who have proper equipment if trees are tall or many trees are to be treated. Imidacloprid** (see note) may be used as a systemic.

 

Spider mites

After new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), apply acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Treat undersides of leaves as well as upper sides.

Holly

(Ilex)

Cottony maple leaf scale

Use horticultural oil for a dormant spray in April. For crawlers, spray in June (802–1265 GDD) with acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Native holly leafminer

Remove and destroy mined leaves before May. If needed, spray in mid-May (198–298 GDD) and again in early July (1029-1266 GDD), using acephate, carbaryl, or lambda-cyhalothrin. Or use disulfoton or imidacloprid**, as a systemic.

 

Scales

Treat for crawlers with acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Spider mites

 

spider mite

After new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, Mite-X (plant extracts), or neem oil. Treat undersides of leaves as well as upper sides. Or use disulfoton, as a systemic.

 

Twobanded Japanese weevil

Handpick and remove, if possible. Spray in late July or in August (1644–2271 GDD), with neem oil.

 

Whitefly

Apply acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use a systemic: disulfoton, or imidacloprid** (see note).

Honeylocust

(Gleditsia)

Honeylocust plant bug

Spray from late April through early May (58–246 GDD), with carbaryl or lambda-cyhalothrin.

Pod gall midge

Spray in mid-May (199–229 GDD) with carbaryl.

Scales

Treat for scale crawlers with acephate, cyfluthrin, horticultural oil, imidacloprid**, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil.

 

Spider mites

After new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), apply acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, Mite-X (plant extracts), or neem oil. Treat undersides of leaves as well as upper sides.

Honeysuckle

(Lonicera)

Honeysuckle aphid

Causes witches’-brooming. Resistant cultivars are available. If needed, spray as leaves begin spring expansion, 2 weeks later, and again 4 weeks after that, using acephate, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Leafroller

At first sign of insects, apply cyfluthrin, lambda-cyhalothrin, neem oil, or spinosad.

 

 

Spider mites

After new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), apply acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, Mite-X (plant extracts), or neem oil. Treat undersides of leaves as well as upper sides. Or use disulfoton, as a systemic insecticide.

 

Whitefly

whitefly

Large populations may require the use of insecticides. Treat undersides of leaves in early June (448–700 GDD), mid-July, and mid-August (1250–1500 GDD). Use acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use a systemic: disulfoton, or imidacloprid** (see note).

Horsechestnut and Buckeye

(Aesculus)

Leaf blotch

(Guignardia aesculi,

Phyllosticta paviae)

Follow disease sanitation practices* (see note). On small trees, in spring when new leaves emerge, spray chlorothalonil three times at intervals of 10 to 14 days. For large trees, consult a professional applicator.

Hydrangea

 

Fungal leaf spot

Follow disease sanitation practices* (see note). If needed, apply Bacillus subtilis, chlorothalonil (see note), copper soap (copper octanoate), copper sulfate, myclobutanil, neem oil, or potassium bicarbonate. Note: chlorothalonil may discolor blossoms; apply to foliage only and test on a small area first.

 

 

Powdery mildew

Follow disease sanitation practices* (see note). If needed, apply Bacillus subtilis, chitosan, copper soap (copper octanoate), myclobutanil, neem oil, potassium bicarbonate, or sulfur.

 

Aphids

aphid

Apply if needed: acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Leaftier (caterpillar)

Remove by hand. If needed, spray as soon as noticed. Best results are when larvae are exposed, rather than hidden within tied leaves. Use carbaryl, cyfluthrin, horticultural oil, lambda-cyhalothrin, neem oil, or spinosad.

 

Spider mites

Spray if needed, using acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Good coverage of leaf undersides is important for control. Repeat spraying may be necessary. Or use disulfoton, as a systemic.

Ivy (Boston)

(Parthenocissus)

Fungal leaf spot (Guignardia, anthracnose)

Follow disease sanitation practices* (see note). Apply copper ammonium carbonate following label directions.

 

Powdery mildew

Follow disease sanitation practices* (see note). Apply Bacillus subtilis, chitosan, or copper ammonium carbonate.

 

Japanese beetle

Handpick and remove adults, where possible. If needed (usually in July), apply acephate, cyfluthrin, lambda-cyfluthrin, malathion, neem oil, or pyrethrins plus PPB. Or use imidacloprid** (see note) as a systemic.

 

Scales

Spray at two-week intervals during June and July. Use acephate, cyfluthrin, horticultural oil, lambda-cyfluthrin, or neem oil. Or use imidacloprid** as a systemic.

 

Spider mites

Spray in May and repeat only if needed. Use acephate, insecticidal soap (potassium salts of fatty acids), lambda-cyfluthrin, malathion, neem oil, or Mite-X (plant extracts).

Ivy (English)

(Hedera)

Anthracnose (Colletotrichum)

Follow disease sanitation practices* (see note). Apply azoxystrobin (not near apples), Bacillus subtilis, copper ammonium carbonate, or potassium bicarbonate.

 

Bacterial leaf spot (Xanthomonas hederae)

Follow disease sanitation practices* (see note). Apply Bacillus subtilis following label directions.

 

Scales

Spray at two-week intervals during June and July, with acephate, cyfluthrin, horticultural oil, lambda-cyfluthrin, or neem oil. Or use imidacloprid** as a systemic.

 

Spider mites

Spray in May and repeat only if needed. Use acephate, insecticidal soap (potassium salts of fatty acids), lambda-cyfluthrin, neem oil, or Mite-X (plant extracts).

Juniper

(Juniperus)

Cedar-apple/cedar hawthorn rust

Remove galls in early spring. Beginning in early August, spray with copper ammonium carbonate or potassium bicarbonate.

 

Tip blight (Phomopsis, Kabatina, etc.)

Follow disease sanitation practices* (see note).

Confirm diagnosis and, if appropriate, spray at two week intervals throughout the growing season or according to label directions.

Depending on the blight fungus species (check product labels prior to purchase), apply azoxystrobin (not near apples), potassium bicarbonate, or propiconazole.

Juniper tip blight

 

 

Arborvitae leafminers

Treat for larvae with acephate or lambda-cyfluthrin in mid-May (150–260 GDD) with a second application in early August (1800–2200 GDD). Or use imidacloprid** (see note) as a systemic.

 

Juniper scale

juniper scale

Symptoms include yellowing foliage, turning brown in severe infestations. Prune out infested areas, where possible. Apply horticultural oil for dormant spray in mid- to late April (22–148 GDD). In mid- to late June and early July (707–1260 GDD), use acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Juniper webworm

Spray in late July through early August (1645–1917 GDD), using acephate, carbaryl, or spinosad.

 

Spider mites

After new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, Mite-X (plant extracts), or neem oil. Treat undersides of leaves as well as upper sides.

Lilac

(Syringa)

Powdery mildew

Follow disease sanitation practices* (see note). Apply Bacillus subtilis, chitosan, chlorothalonil, copper ammonium carbonate, or propiconazole.

 

Bacterial blight

Follow disease sanitation practices* (see note). Apply Bacillus subtilis or copper ammonium carbonate.

 

Lilac borer/ash borer

Prune out and destroy infested portions. Imidacloprid** (see note) may be used as a systemic.

 

Lilac leafminer

Spray in mid- to late May (246–363 GDD) and again in mid- to late July (1388–1644 GDD) with acephate, lambda-cyhalothrin, or permethrin. Or use imidacloprid** as a systemic.

 

Oystershell scale

oystershell scale

If scale infestations are small, prune out affected plant parts. Horticultural oil may be applied as a dormant spray in April (7–91 GDD). Treat for crawlers in late May through mid-June (363–707 GDD), using acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, malathion, neem oil, or permethrin. Or use imidacloprid** (see note) as a systemic.

 

Twobanded Japanese weevil

Spray in late July or in August (1644-2271 GDD) with neem oil. Imidacloprid** (see note) may be used to control the larvae.

 

White prunicola scale

Signs and symptoms include a white coating on the trunk and twigs, and dieback. Prune out where possible. Rather than applying pesticides, commercial applicators may powerwash to remove scales. Horticultural oil may be used as a dormant spray in April (35–145 GDD). Treat for crawlers once in mid-June to early July (707–1151 GDD) using cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** as a systemic.

Linden (littleleaf)

(Tilia)

Japanese beetle

Handpick and remove, where possible on small trees. If needed, use acephate, cyfluthrin, lambda-cyhalothrin, malathion, neem oil, or pyrethrins plus PPB. Or use imidacloprid** as a systemic.

London plane and Sycamore

(Platanus)

Anthracnose

Follow disease sanitation practices* (see note). For small trees only, spray with chlorothalonil, copper ammonium carbonate, or copper soap (copper octanoate). For large trees consult a professional applicator.

Note: Check pesticide label for plant species.

Powdery mildew

Follow disease sanitation practices* (see note). If needed, spray with Bacillus subtilis, or copper ammonium carbonate.

 

American plum borer

Imidacloprid** (see note) may be used as a systemic.

 

Lace bug

Spray in mid-May (239–363 GDD) and again in mid-July (1266–1544 GDD) with acephate, carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin. Or use imidacloprid** as a systemic.

 

Scales

Treat for scale crawlers using cyfluthrin, horticultural oil, imidacloprid**, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin.

Magnolia

Magnolia scale

If scale infestations are small, it may be possible to prune out affected twigs or scrub scales off branches. Horticultural oil may be used as a dormant spray in April (22–91 GDD). In early October, spray for crawlers on branches using cyfluthrin, horticultural oil, lambda-cyhalothrin, or malathion. Two fall applications 7–10 days apart may be needed. Or use imidacloprid** as a systemic.

Maple

(Acer)

Anthracnose

Follow disease sanitation practices* (see note). For small trees only, apply azoxystrobin (not near apples) or copper ammonium carbonate. For large trees, consult a professional applicator.

 

Tar spot

(Rhytisma)

Follow disease sanitation practices* (see note). In most years, when tar spot develops later in the season, it does not cause major damage to the tree. Rake up and remove dead leaves in the fall, to reduce infection the following year.

On Norway maple, especially in drought years, tar spot can become abundant enough to cause premature leaf drop. For large trees, consult a professional applicator.

 

Aphids

Use acephate (may cause leaf injury on sugar or red maples), cyfluthrin, horticultural oil, insecticidal soap (but not on Japanese maples), lambda-cyhalothrin, malathion, or Mite-X (plant extracts). Or use imidacloprid** (see note) as a systemic.

 

Boxelder bug

These feed on developing seeds of maples (Acer species), including boxelder and others. If numbers of nymphs or adults are seen, apply carbaryl, cyfluthrin, or lambda-cyhalothrin.

 

Cottony maple scale, and Cottony maple leaf scale

If scale infestations are small, prune out affected plant parts. Horticultural oil may be applied as a dormant spray in mid- to late April. In late June and early July (801–1265 GDD), treat for crawlers using acephate (may cause leaf injury on sugar or red maples), carbaryl, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or malathion. Or use imidacloprid** (see note) as a systemic.

 

Forest tent caterpillars

Parasites are often abundant enough to provide partial control. In mid- to late May (192–363 GDD), small trees may be treated with Bt (Bacillus thuringiensis ssp. kurstaki), acephate (may cause leaf injury on sugar or red maples), carbaryl, lambda-cyhalothrin, or malathion. For large trees, consult a professional applicator.

 

Maple bladdergall (eriophyid) mites

The tiny leaf galls may be aesthetically displeasing, but are not seriously harmful to the tree. Horticultural oil labeled for mites may be used as a dormant spray in mid- to late April.

Mountain ash

(Sorbus)

Fire blight

Prune out infected parts when plants are dry, making each cut several inches below areas of visible discoloration. Disinfect tools between cuts. Apply Bacillus subtilis (for suppression).

 

Mountain ash sawfly

mt

When larvae are observed, usually in early to mid-June (448–707 GDD), apply carbaryl, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or spinosad. Or use imidacloprid** (see note) as a systemic.

 

Rose Chafer

and Japanese Beetle

Handpick and remove, where possible. If needed, use carbaryl, cyfluthrin, lambda-cyhalothrin, malathion, or neem oil. NOTE: Check product label for which type of beetle is listed. Spray when observed and continue at weekly intervals until beetle season is over. Or use imidacloprid** (see note) as a systemic.

 

Roundheaded appletree borer

The adult beetles make exit holes in the bark near the tree base, after tunneling in the trunk as larvae. To prevent adults from laying eggs, ring the bottom 12–24 inches of the trunk with oviposition barriers in May. Use wire mosquito netting, hardware cloth, or several layers of newspapers. Barriers should be loose except at the bottom (cover with soil) and top (tie with cord). Remove barriers at the end of the season (October). Imidacloprid** (see note) may be used as a systemic.

 

Spider mites

Treat after new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD). Use horticultural oil (summer or all-season type), insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, Mite-X (plant extracts), or neem oil. Treat undersides of leaves as well as upper sides.

Mountain laurel

(Kalmia)

Fungal leaf spot

Follow disease sanitation practices* (see note). Apply Bacillus subtilis (for suppression) or chlorothalonil.

 

Black vine weevil

For adult weevils, remove by hand, use pitfall traps, or burlap collars. Apply lambda-cyhalothrin if needed. To control larvae, imidacloprid** may be used as a systemic.

 

Borer

To control larvae, imidacloprid** (see note) may be used as a systemic.

 

Lace bug

Natural enemies are rarely abundant enough to affect damaging populations. Infestations are more severe in sunny, exposed sites. In early to mid-May (120+ GDD), spray undersurfaces of leaves with carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), or lambda-cyhalothrin. Or use a systemic: disulfoton, or imidacloprid**.

 

Whitefly

Large populations may require the use of insecticides. In early June (448–700 GDD), mid-July, and mid-August (1250–1500 GDD), treat undersides of leaves with cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or malathion. Or use a systemic: disulfoton, or imidacloprid** (see note).

Oak

(Quercus)

 

 

 

P56LARVAB Gypsy moth larva

Anthracnose and other leaf spot diseases

Follow disease sanitation practices* (see note). If disease has been severe, spray with azoxystrobin (not near apples), chlorothalonil (check label: some products should only be used on oaks in the red oak group, not white oaks), or copper ammonium carbonate. Or use sulfur or propiconazole, depending on the disease. Check labels to see which kinds of leafspots are listed.

Blotch leafminers

Control is dependent on early treatment when mines are less than 1/4 inch long (533–912 GDD). Apply acephate, carbaryl, lambda-cyhalothrin, permethrin, or spinosad. Or use imidacloprid** (see note) as a systemic.

Cankerworms

Treat when first observed in the spring. Use Bt (Bacillus thuringiensis ssp. kurstaki), carbaryl, cyfluthrin, lambda-cyhalothrin, permethrin, or spinosad.

Gypsy moth

Remove and destroy egg masses over winter. If needed, spray foliage in May after larvae hatch (90–448 GDD). Use acephate, Bt (Bacillus thuringiensis ssp. kurstaki), carbaryl, cyfluthrin, lambda-cyhalothrin, or spinosad. If using Bt, apply before larvae reach 1 inch in length.

Leaf galls and Oak galls

Although these may be aesthetically displeasing, galls on the leaves generally do not cause major damage to the tree. If desired, handpick and destroy galls, where practicable. Carbaryl may be used for the tiny gall wasps and gall midges, if necessary.

Leaftiers

This pest is minor, and control is usually not necessary. Cyfluthrin, lambda-cyhalothrin, neem oil, or spinosad may be used.

Scales

Treat for scale crawlers with acephate, cyfluthrin, horticultural oil, imidacloprid**, lambda-cyhalothrin, malathion, or neem oil.

 

Skeletonizer

Spray foliage in early June (448–707 GDD) and if needed, again in early August (1798–2155 GDD). Use carbaryl, cyfluthrin, lambda-cyhalothrin, or spinosad.

Pachysandra

Volutella blight

Follow disease sanitation practices* (see note). When new leaf growth starts, spray with chlorothalonil following label directions.

P57LEAVESC

 

Euonymus scale

Signs and symptoms include yellow spots on leaves and gray-white scurfy material on stems. Where possible, prune out scale-infested branches. Horticultural oil may be used as a dormant spray in mid-April to early May (35–120 GDD). In early to mid-June (533–820 GDD); and again in mid-July (1150–1388 GDD), use horticultural oil, cyfluthrin, insecticidal soap (potassium salts of fatty acids), malathion, or neem oil. Or use imidacloprid** (see note) as a systemic.

Pieris

See Andromeda.

 

Pine

(Pinus)

Diplodia tip blight (Sphaeropsis)

Follow disease sanitation practices* (see note). Apply potassium bicarbonate or propiconazole, if needed.

 

Aphids

Apply horticultural oil as a dormant spray in mid- to late April. When aphids are seen during the growing season, acephate, cyfluthrin, lambda-cyhalothrin, neem oil, or Mite-X (plant extracts) may be applied. However, pesticides applied to foliage may kill predatory insects, which could otherwise help control insect pests. Or use imidacloprid** (see note) as a systemic.

 

European pine shoot moth

Prune out and destroy dead buds and dying shoots. Spray in late April (34–121 GDD) with carbaryl, malathion, or permethrin.

 

Gypsy moth

Remove egg masses over winter. Gypsy moth is usually not a serious problem on pine unless population levels are high. If necessary, spray in mid- to late May or when needed, using carbaryl, cyfluthrin, lambda-cyhalothrin, or spinosad.

 

Nantucket pine tip moth

Spray in May (121–448 GDD) and again in late July through early August (1514–1917 GDD). Use acephate, lambda-cyhalothrin, or permethrin. Or use imidacloprid** (see note) as a systemic.

 

Pine bark adelgid

Remove adelgids from the bark with a high pressure wash or scrub off with a brush. If needed, apply horticultural oil to the bark in April (22–58 GDD). Or use insecticidal soap (potassium salts of fatty acids), or imidacloprid** (see note).

 

Pine false webworm

In early June, apply lambda-cyhalothrin or spinosad. Or use imidacloprid** (see note) as a systemic.

 

Pine needle scale

Use horticultural oil for dormant treatment in mid-April. In late May (298–448 GDD) and late July (1290–1917 GDD), treat for crawlers using acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, malathion, or permethrin. Or use imidacloprid** as a systemic.

 

Pine sawflies

Hand pick or prune off and destroy colonies. Or spot treat when observed, using acephate, carbaryl, lambda-cyhalothrin, or spinosad. Or use imidacloprid** (see note) as a systemic.

 

Pine thrips

(especially on

Japanese black pine)

Treat once, in mid-April to Mid-May using malathion or permethrin (for thrips on exposed surfaces). Or use imidacloprid** as a systemic.

 

Pine tortoise scale

Use horticultural oil for dormant treatment in mid- to late April (58–148 GDD). In mid- to late June (618–1050 GDD), treat for crawlers using acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, or malathion. Or use imidacloprid** as a systemic.

 

Spittlebug

Remove spittle masses and insects by hand. If needed, spray in early to mid-May (148–298 GDD) using acephate, carbaryl, or lambda-cyhalothrin.

 

White pine aphid

Treat in April (7–121 GDD), again early to mid-May (121–246 GDD), and if needed, again in mid-August (1917–2271 GDD). Apply cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, permethrin, or Mite-X (plant extracts). Or use imidacloprid** as a systemic.

 

White pine weevil

Cut out and destroy wilted or dead leaders by the end of June. No pesticides are registered for homeowner use.

 

Zimmerman pine moth

Some products containing permethrin may be used; check labels.

Privet

(Ligustrum)

Privet rust mite

Treat with carbaryl or Mite-X (plant extracts) in the last 10 days of May through mid-June (298–802 GDD) and in mid-July (1266–1515 GDD). Apply to both sides of foliage.

 

Privet thrips

Treat once in mid-May to early-June (192–618 GDD) and once during first 10 days of July (1029–1266 GDD). Use carbaryl, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Scales

Prune out severely infested plant parts. Treat for crawlers using acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Twobanded Japanese weevil

Spray in late July or in August (1644–2271 GDD) with neem oil. Or use imidacloprid** as a systemic.

 

White prunicola scale

Signs and symptoms include white coating on trunk and twigs, and dieback. Prune out where possible or wash off scales with high pressure power washing. Horticultural oil may be used as a dormant spray in April (35–145 GDD). Treat for crawlers one time in mid-June to early July (707–1151 GDD) using cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

Pyracantha

See Firethorn.

 

Quince

(Chaenomeles)

Fire blight

Prune out infected parts when plants are dry, making each cut several inches below areas of visible discoloration. Disinfect tools between cuts. Apply Bacillus subtilis (for suppression) if needed.

 

Rust

Follow disease sanitation practices* (see note). Apply chlorothalonil following label directions.

Rhododendron

(Also see Azalea.)

Rhododendron gall midge

Open-grown plants and those with good air circulation are less susceptible to injury. Remove gall-deformed leaves by hand. Apply spinosad or carbaryl at foliage budbreak in mid- to late May (192–363 GDD).

Rose

(Rosa)

Black spot

Follow disease sanitation practices* (see note).

Many pesticides are available including: Bacillus subtilis, chlorothalonil, copper ammonium carbonate, copper soap (copper octanoate), copper sulfate, myclobutanil, neem oil, potassium bicarbonate, propiconazole, and sulfur. Use according to label directions.

P59ROSELEAF

 

Botrytis blight

(gray mold)

Follow disease sanitation practices* (see note). If blight symptoms develop during wet periods, apply azoxystrobin (not near apples), Bacillus subtilis, chlorothalonil, copper ammonium carbonate, copper soap (copper octanoate), myclobutanil, neem oil, or potassium bicarbonate.

 

Crown gall

Inspect new transplants carefully before adding to the landscape. No pesticides are currently available for home use.

 

Powdery mildew (Sphaerotheca)

Follow disease sanitation practices* (see note). When disease appears, apply azoxystrobin (not near apples), Bacillus subtilis, copper ammonium carbonate, copper soap (copper octanoate), copper sulfate, lime sulfur (calcium polysulfide), myclobutanil, neem oil, potassium bicarbonate, propiconazole, or sulfur.

 

Rust

(Phragmidium)

Follow disease sanitation practices* (see note). When rust pustules are first seen on lower leaf surfaces, apply azoxystrobin (not near apples), Bacillus subtilis, copper soap (copper octanoate), copper sulfate, lime sulfur (calcium polysulfide), myclobutanil, neem oil, potassium bicarbonate, propiconazole, or sulfur.

 

Aphids

Spray when aphids first appear and follow label directions for additional applications if needed. Use acephate, carbaryl, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, Mite-X (plant extracts), or neem oil. Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Japanese beetle

Japanese beetle

Handpick and remove. If necessary, spray when observed and continue at weekly intervals until beetle season is over. Use acephate, carbaryl, cyfluthrin, lambda-cyhalothrin, malathion, neem oil, permethrin, or spinosad. Or use imidacloprid** (see note) as a systemic.

 

Leafhopper

Spray 3 times at four-week intervals, beginning in June. Use acephate, carbaryl, cyfluthrin, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or malathion. Or use a systemic: disulfoton, or imidacloprid**.

 

Rose chafer

Rose chafer

This beetle has few natural enemies. Handpick beetles and remove. If needed, spray in early June when beetles are present using carbaryl, neem oil, or permethrin.

 

Rose midge

Use acephate or lambda-cyhalothrin following label directions.

 

Roseslug and other sawfly larvae

Handpick where possible. If needed, spray with acephate, carbaryl, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or spinosad. Or use imidacloprid** (see note) as a systemic.

 

Spider mites

If needed, use acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Treat undersides of leaves as well as upper sides. Or use disulfoton, as a systemic.

Spruce

(Picea)

 

Rhizosphaera needle cast

This disease is most often found on trees weakened by other causes and is rarely severe enough to warrant control measures. If damage is not tolerable, spray with chlorothalonil. Make first application when new growth is 1/2 to 2 inches long and make additional applications at 3 to 4 week intervals while conditions favor disease.

 

Cooley spruce gall adelgid

Apply horticultural oil as a dormant spray in mid- to late April (22–91 GDD) just before buds begin to break. In mid-September (1850–1950 GDD), apply carbaryl, horticultural oil, or insecticidal soap. Or use imidacloprid** (see note) as a systemic.

P60SPRUCE

Cooley spruce gall (pineapple shaped galls at tip of spruce shoot)

 

Eastern spruce gall adelgid

This adelgid makes galls at the base of new shoots on Norway spruce. Spray in mid-April to early May (22–170 GDD) or treat in mid- to late September when insects emerge from galls and majority of galls are open. Use horticultural oil or insecticidal soap. Or use imidacloprid** as a systemic. Caution:

Horticultural oils may discolor the foliage of Blue spruce.

 

Sawfly

Hand pick or prune off and destroy colonies. If needed, spot treat when seen using acephate, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, or spinosad. Or use imidacloprid** as a systemic.

 

Spider mites

Horticultural oil may be used as a dormant spray in April (7–121 GDD) before new growth begins. After new growth begins in mid- to late May (192–363 GDD) and in late August through mid-September (2375–2806 GDD), treat with acephate, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, neem oil, or Mite-X (plant extracts). Treat undersides of leaves as well as upper sides.

 

Spruce bud scale

Horticultural oil may be used as a dormant spray in mid-April (22–121 GDD). Treat for crawlers in late June and early July using cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

 

Spruce needle miner

Prune out clusters of needles held together by silk in early spring. In early to mid-June (448–802 GDD), if needed, apply carbaryl.

 

White pine weevil

White pine weevil

Cut out and destroy wilted or dead leaders by the end of June. No pesticides are registered for homeowner use.

Sycamore

See London plane.

 

Taxus

(Yew)

 

 

Black vine weevil

(Taxus weevil)

 

black vine weevil

 

Black vine weevil injury

Handpick and remove adults when seen. Pitfall traps or beating sheets can help monitor adult activity. To control adults, use acephate or lambda-cyhalothrin in mid-June (about 10 days earlier for Long Island) and early to mid-July. Apply full coverage spray to foliage and the soil beneath plants. Or use imidacloprid** (see note) as a systemic.

Entomophagous nematodes may be used for the soil-dwelling stage (larvae) during late summer to early fall.

 

Fletcher scale

If scale infestations are small, prune out affected plant parts. Use horticultural oil as a dormant spray in April (35–148 GDD). Treat for crawlers in early July (1029–1388 GDD) and early September (2515–2800 GDD) using acephate, horticultural oil, lambda-cyhalothrin, or malathion. Or use imidacloprid** (see note) as a systemic.

 

Mealybug

Use horticultural oil as a dormant spray in April (7–91 GDD). Spray again in mid-May through early June (246–618 GDD) using carbaryl, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or permethrin. Or use imidacloprid** (see note) as a systemic.

Viburnum

Downy mildew (Plasmopara)

Follow disease sanitation practices* (see note). Apply Bacillus subtilis (for suppression) in spring, following label directions.

 

Aphids

Spray in May, and repeat only if needed. Use acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, neem oil, or permethrin. Or use a systemic: disulfoton, or imidacloprid** (see note).

 

Cottony maple leaf scale

Use horticultural oil as a dormant spray in April. For crawlers, spray in June (802–1265 GDD) using acephate, cyfluthrin, horticultural oil, lambda-cyhalothrin, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Viburnum leaf beetle

This beetle is a recent invasive insect in the Northeast. Remove and destroy twigs with egg masses (usually on newest growth) between October and April. If needed, spray with cyfluthrin or pyrethrins plus PPB when larvae first appear in early May (75–100 GDD) or if damage from adults (mid- to late summer) is excessive. Or use imidacloprid** (see note) as a systemic.

Willow

(Salix)

Aphids

Spray in late May, and repeat in mid- to early July if aphid populations are still present. Apply acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, Mite-X (plant extracts), or neem oil. Or use imidacloprid** as a systemic.

 

Scales

Treat for crawlers using acephate, cyfluthrin, horticultural oil, insecticidal soap (potassium salts of fatty acids), lambda-cyhalothrin, malathion, or neem oil. Or use imidacloprid** (see note) as a systemic.

 

Willow leaf beetle, Imported willow leaf beetle

In mid-May to early June (192–448 GDD) apply acephate, carbaryl, cyfluthrin, or neem oil. Or use imidacloprid** as a systemic.

Yew

(Taxus)

See Taxus.

 

 

* Disease Sanitation Practices: Avoid crowding plants; allow air to circulate around and within plants. Prune to thin plants or plantings and/or to remove diseased parts. Prune only when conditions are dry, and, where feasible, disinfect pruning tools between cuts or between plants. Discard all diseased tissue and in autumn, rake and discard or destroy all fallen leaves, fruit, and branches. Avoid wetting foliage overnight or for long periods of time.

** Imidacloprid: Products containing imidacloprid are not registered for use in certain New York City and Long Island counties (Kings, Queens, Nassau, and Suffolk). Most formulations of imidacloprid once available to homeowners are now classified as restricted-use (for professional application only) in New York State. Check product status and label prior to purchase.