More species and cultivars of ornamental plants are growing in nurseries and in the landscape than all other kinds of cultivated crops combined. While this is a statement of pride among ornamental horticulturists, it is likewise true that an even greater number of pest species find these plants and use them as food, causing an expenditure of time and dollars in added maintenance costs.

Concise pesticide guidelines are given in this publication for managing more than 150 species of insects and mites on over 50 kinds of ornamental trees and shrubs in the four plant zones of New York. Practical and effective control of insects and mites that attack ornamental trees and shrubs can be achieved by recognizing the pests, understanding their life histories, and using a skillfully planned integrated pest management (IPM) program.

IPM goes beyond the use of chemical pesticides and includes every means of pest control that may be applied under a given set of circumstances. Useful pest control techniques must be compatible, so IPM programs may vary from nursery to nursery or landscape to landscape and may require professional assistance to organize and maintain. What follows are but fragments of the IPM concept. Chemicals in some form - pesticides, pheromones, attractants, or repellents-represent the most pragmatic and in some cases the only operational IPM tactic that can be used successfully by the traditionally trained horticulturist. We recognize that the use of some chemicals is not in the best interest of the total environment. The database required to implement an IPM program for the great number of woody ornamental plants is so massive that computers, or access to them, are needed by both those who prepare guidelines and those who use them. In lieu of an IPM program, nursery and arboricultural managers must rely on experience and pesticides.

In the near future, growing and maintaining landscape plants will require specialists, either consultants or permanent staff, who fully understand the science and technology of pest management and have access to the necessary database. Where growing and maintaining plants interferes with any element of environmental stability, the pressure for correction will be socially and politically enforced. In this respect the future has already begun.

2.2 How to Use the Insect and Mite Chapter

"Insect Pest Management" is divided into three sections. Section 2.5 gives an overview of current integrated pest management thought, rationale, and goals, provides some of the science backing up biorational pest management, and includes examples of most of the biorational tools and tactics. Section 2.6 contains information on pesticide toxicity and hazards to people, wildlife, and plants; timing, rates, and systems of application; and some precautions. Pay particular attention to the limitations as well as the advantages of each material. Section 2.8 provides specific information on where and when to spray or treat and what to use for each pest. A seasonal appearance guide of pests according to host and suggested timing for control measures is included. To find information on a pest when the accepted common name is not known, consult Table 2.8.11 and look under the name of the plant in question.

2.2.1 Suggested Procedure

1. Become thoroughly familiar with all the material in all sections.

2. Consider the advantages, disadvantages, and precautions for each management method or pesticide and study the general discussion in Section 2.6. There is a wealth of concentrated information in tabular form, allowing for easy access.

3. Sections 2.6 and 2.8 are devoted primarily to chemical control systems; this is necessary because long-range pest control measures have been delayed or ignored, resulting in the need for emergency measures. In Section 2.8 find and note the pests of importance to you. Note the best time to apply management techniques. (It may be helpful to make these notations on a monthly calendar.) The proper biological timing of control measures for each pest in each locality can be achieved through experience, by using the growing degree-day system, or by phenological indicator plants (see Table 2.9.1). By selecting a combination of the most effective, safe, and useful chemical along with cultural and biological methods, you can determine a seasonal schedule of management for various plant types under your care.

4. Keep a record of treatments and schedules used from year to year to accumulate seasonal experience for spraying. Records of normal growth phenomena such as bud development and flowering are useful in documenting the proper time for treatment in your geographical area.

2.3 About the Tables

Sections 2.6 and 2.8 contain lists and tables that permit quick access to a mass of pest management information. Be certain that you understand the footnotes and how to use these tables. To assist in diagnosis (identification) of a pest, first look at Table 2.8.1. Find the plant of concern, then note the common or "key" pests associated with the plant. Numbers following the names of pests correspond to pages with descriptions in Insects That Feed on Trees and Shrubs, second edition, published by Cornell University Press. Plate numbers showing illustrations are indicated in boldface type. Next, turn to Table 2.10.1, remembering the name of the suspect. Entries for each pest include signs and/or symptoms of infestation, management options, timing of treatment, and IPM considerations. If you are interested in the characteristics of a particular pesticide-what it will control, formulations available, EPA numbers, nursery versus landscape uses, restricted-entry intervals, phytotoxicity, and other precautions-see Table 2.7.1. If you are interested in scheduling treatments by season and month, see Table 2.9.1. For example, in the dormant season about 15 kinds of arthropod pests are vulnerable to horticultural mineral spray oils.

2.4 Insect and Mite Control for Propagation Ranges, Greenhouses, and Perennials

Control of insect and mite problems for interior use in greenhouses, arboreta, and interiorscapes is handled separately in Guide for the Integrated Management of Greenhouse Florist Crops-Management of Pests and Crop Growth. Herbaceous perennials are covered in Pest Management Guide for the Production of Herbaceous Perennials. Both of these publications are available through the Pesticide Management Education Program Educational Resources office (phone: 607-255-7282; email: patorder@cornell.edu).

2.5 Biorational Pest Management Tools and Tactics

2.5.1 "Biorational" Controls

Biorational tactics begin with applicable cultural and mechanical practices such as diverse cropping, crop rotation, and roguing of sick plants; traps using food baits, light, and color as attractants continue to be useful. Some of these old practices are as good today as they were when first introduced. They may not stand alone, however, and additional tactics for control may be needed. The term "biorational" means to be environmentally conservative, that is, protect the desired plant from pests while protecting other organisms from harmful side effects in the nearby and total environment.

Reducing the population or doing away with a pest species, while important, does not override the need for a rational approach to management. Biological control using parasites and predators of the pest species represents environmental conservatism and natural order. Such tactics often require a change in contemporary pest control attitudes. The biologicals depend on a reservoir of pest species to remain alive, but because the reservoir pests do damage, one must decide how much damage is tolerable. Under the most successful conditions, parasites and predators need care and must be conserved. Some pest management businesses have biological control specialists, but most of this work is done under the direction of government agencies and land grant educational institutions. While not to discourage one from using insects to control pest species, such tactics should be brought into an integrated pest management program with the advice of a biological control specialist. A commitment to monitoring and maintenance is necessary to make it work.

Biorational tools, as covered here, also include information about natural plant resistance to pests. A functional knowledge of resistant plants may simply be a list of cultivars or species available to replace the nonresistant ones. Few such lists exist, but they are available for plants resistant to euonymus scale, lace bug on cotoneaster and pyracantha, hawthorn, and mountain ash; and bronze birch borer as examples. Some of these (as well as susceptible plants) are noted in Table 2.10.1 and in the publication Pest-Resistant Key Ornamental Plants by D. Smith-Fiola (available from Landscape IPM Enterprises, 5214 Hollow Tree Lane, Keedysville, MD 21756)). Check with your local Cooperative Extension office for additional publications and information on this topic. Some plants have evolved both physical and chemical defenses against their arthropod enemies. Such defenses are genetically prescribed. The leaf epidermis or bark surface is the first barrier between phytophagous insects and host plants. The foliage surface environment may be hostile to a food-searching insect. The epidermal glands of a leaf may produce defensive substances that are sticky or produce wax difficult for the mouthparts to penetrate. Cells may make and store toxic substances such as tannins and steroids. A few plants of a species may produce trichomes that make insect movement difficult or they may produce quantities of defense chemicals that result in less insect depredation. Such plants have developed a natural resistance.

The selection of such plants for breeding stock is highly desirable but left largely to plant propagators and traditional geneticists because patent rights may be obtained. Notice of pest-resistant species may come from large nurseries or researchers at universities. Recent work in Michigan, for example, has provided evidence that our native birch, Betula papyrifera, is more resistant to bronze birch borer than any other white-bark birch. Gene manipulation or genetic engineering for obtaining pest-resistant ornamental plants is possible now, delayed only by funding and cooperative work between horticultural and molecular biologists with mutual genetic and high-tech interests.

Many chemical classes are considered to be biorational pesticides, repellents, or attractants. Some pesticides of botanical origin such as rotenone, pyrethrum, and neem seed extract are thought to be environmentally friendly and fit a biorational definition. Not all chemicals of botanical or natural origin are environmentally neutral, however. Many known biochemicals affect the behavior of insects, such as those classified as kairomones, pheromones, and insect growth regulators (IGRs). Kairomones are volatile chemicals produced by plants that attract insects, incite feeding or egg-laying, or otherwise induce the insect to remain on a host plant. An insect historically associated with a particular plant species is able to recognize such kairomone "odors" as originating from its food plant. Examples of kairomones include phenolic compounds found in sap and resin of conifers that attract bark beetles and the plant oil extract geraniol, which has long been used as an attractant in Japanese beetle traps. Commercial exploitation of this class of biochemicals for pest management purposes is mostly on the horizon.

Arthropod pheromones are also useful management tools, particularly for detecting pests and timing control actions. More on pheromones and pheromone traps is discussed later in section 2.6.

IGRs were first recognized as useful with the discovery of the juvenile hormone biochemicals in insects. Some plants even use this chemistry as a form of protection. IGRs act on the hormonal system of immature insects; they generally do not kill adult insects and have a delayed effect. Therefore, timing applications to coincide with early immature stages is important and one should not expect to see immediate control. Treated insects may stop feeding, however. At least three major groups of IGR insecticides are now in use. Juvenile hormone mimics act like natural juvenile hormone in insects, the presence of which ensures that the next molt will be to another immature (larval) stage in treated insects. Affected insects usually do not reach adulthood or die while molting to the next larval stage. The insecticide pyriproxyfen (Distance) is a juvenile hormone mimic. Chitin biosynthesis inhibitors interfere with the production of chitin, an essential component of the insect shell or skin. Insects affected by these materials are not able to molt successfully. Novaluron (Pedestal) and diflubenzuron (Dimilin, Adept) are members of this group that primarily target butterfly and moth caterpillars, although they are also used for other kinds of insects. Dimilin, for example, is used against early stages of gypsy moth and other caterpillars and also has some ovicidal activity; Adept is also used in greenhouses to control fungus gnat larvae. Cyromazine (Citation) is another kind of chitin biosynthesis inhibitor, disrupting molting of fly larvae such as serpentine leafminers. A third group called ecdysone agonists or ecdysone antagonists disrupt molting by interference with the normal operation of ecdysone, a hormone important in the insect molting process. Treated insects may not be able to emerge normally. Azadirachtin (Azatin XL, Ornazin, etc.) and tebufenozide (Confirm) are in this category. Derived from neem seed oil, azadirachtin has been used for thousands of years but only recently commercialized for horticulture in this country. It has some systemic activity when applied to roots and Ornazin is also labeled for trunk injection, although azadirachtin is primarily a foliar insecticide.

Some pesticides are microbes or derived from them. Bacillus thuringiensis kurstaki (Btk) bacteria produce a protein crystal endotoxin that disrupts the gut of butterfly and moth caterpillars. Formulations of the endotoxin are important insecticides used on ornamentals, vegetables, and other plants. Abamectin and spinosad are derived from the soil microorganisms Streptomyces avermitilis and Saccharopolyspora spinosa, respectively. Several commercial preparations are available that consist of spores of the insect-pathogenic fungus Beauveria bassiana. Successful use of microbial pesticides requires detailed knowledge of the pest's biology and phenology and its relationship to its host plant(s). When this knowledge is used in planning and is applied by people who understand the science involved, effectiveness should approach that of synthetic organic pesticides. Some IPM specialists include horticultural mineral oils and insecticidal soaps as biorational pesticides. Both are environmentally friendly in spray dilutions and degrade quickly.

Remember that most ornamental plants in urban and nursery settings are growing in an artificial, contrived environment. Left on their own many of them could not compete and would not survive. Selection often results in the propagation of plants not suitable to the truly natural environment. Such plants generally require more maintenance, including pest management, and in effect are dependent on a range of horticultural chemicals.

2.5.2 Reduced-Risk Pesticides, Minimum-Risk Pesticides, and Biopesticides

See Pesticide Information (Chapter 1).

2.6 Chemical Insecticides

2.6.1 Insecticide Classes and Modes of Action

Not long ago the discussion was of chemical classes such as organophosphates, carbamates, pyrethroids, etc. and the importance of rotating among them as one tactic to manage pesticide resistance. There were few classes to choose from until relatively recently; now there are many new and often confusing chemical class names, such as the chloronicotinyl (neonicotinoid is a more general term) class, represented by the products TriStar, *Merit, *Marathon, etc. Other classes include tetracyclic macrolide (or spinosyns, sometimes referred to as Naturalyte) (Conserve, SpinTor, Entrust), macrocyclic lactone (Avid, etc.) and oxazoline (TetraSan). The emphasis is now rightly placed on rotating among materials with different modes of action, i. e. ways of killing target pests, since materials in different classes may actually be acting similarly or have the same biochemical target site within the pest. Examples of this are the active ingredients clofentezine (in Ovation and Apollo) of the tetrazine chemical class and hexythiazox (*Hexygon, Savey) in the carboxamide class. These two classes have similar modes of action so Ovation and *Hexygon should not be used in rotation. Pyridaben (Sanmite) in the pyridazinone class has a similar mode of action to fenpyroximate (Akari) in the phenoxypyrazole class, therefore these two materials should not be rotated with one another on the same crop in the same season especially in situations where resistant pest populations are likely to develop. To help dispel the confusion, the Insecticide Resistance Action Committee (IRAC) has developed a Mode of Action classification system to simplify the matter and outlines it on a chart, available at http://www.irac-online.org. Some labels now include IRAC numbers representing the material’s mode of action group to help users in selecting among products.

Phytotoxicity of Insecticides

Some plants are sensitive to certain pesticides. The label will name those plants on which the product should not be used. Dimethoate is one of the more variable chemicals, causing foliage injury on elm, andromeda, some varieties of azaleas but not others, Burford and Chinese (but not Japanese) holly, honeylocust, dogwood, crabapple, and maple. Carbaryl may injure tender foliage if plants are wet when treated or present on foliage during several days of high humidity. Endosulfan may injure white birch, redbud, and Anderson yew. Malathion may injure certain junipers, elaeagnus, hibiscus, and some rose varieties. Avid has injured some Shasta daisy cultivars and should not be applied to ferns. These few examples emphasize the importance of reading the label. Check Table 2.7.1 for additional information on particular products.

2.6.2 Timing Spray Applications

The habits of the pest to be controlled affect the timing and frequency of applications. For example, birch leafminer adults emerge from the soil to lay eggs in foliage over an extended period of time. Control treatments to kill newly hatched larvae in the leaves should be delayed until most eggs have been laid, but made before mines exceed 1/4 inch in diameter. If the weather is cool and adult emergence is extended for more than a week, two applications are necessary. With this insect, spraying too early gives poor control. The white pine weevil and general leaf feeders such as the elm leaf beetle are controlled most effectively, however, when the insecticides are applied before their appearance on the plants. In this example the decision to make an early application should have been made during the previous growing season, based on the damage observed.

Residual effectiveness of each chemical also determines the frequency of spray applications. In general, malathion remains as a toxic residue on foliage about two to three days; Sevin remains toxic about one week to 10 days. In Ohio tests (D. Herms, pers. comm.) bark sprays with Onyx for Ips pini provided protection for 15 days at a 16 oz/100 gal. rate but at least 60 days at the 32 oz rate. Astro was also effective for at least 60 days at the 96 and 160 oz/100 gal rates. Results against other pests may differ. We no longer recommend routine scheduled protective cover sprays for insect and mite control. Chemical sprays should be applied only when scouting reveals that a potential problem exists. See Tables 2.10.1 and 2.6.1.

2.6.2.1 Calendar Method

The spraying dates given in these guidelines for each pest are for the average or normal season in southeastern New York State. Spring spray dates in western New York are usually about a week later. In central, eastern, and north central New York they are about 7 to 10 days later. In northern New York and the north and south forks of Long Island, they may be one to two weeks later than in southeastern mainland New York.

Seasonal variations from year to year must be considered. The amount of seasonal adjustment can be determined by comparing budbreak and blooming with what is known to be normal. Early spring climatic variations of the season usually become less pronounced with the approach of summer.

2.6.2.2 Growing Degree-Days (GDD)

The growing degree-day concept of timing the occurrence of various biological phenomena and its use in agricultural systems is not new. As a measure of accumulated solar heat energy, GDD is an arithmetical conversion of daily temperature records to heat units. Plants and cold-blooded animals (e.g., snakes, earthworms, insects) go into a forced physiological dormancy during the winter. To break their diapause (dormancy) requires heat. Each diapausing species (plant or animal) requires a specific amount of accumulated heat to awaken in the spring and show signs of growth. The point of heat accumulation where dormancy breaks is called the threshold of development; the accepted average temperature for plants in New York State is 50°F.

In pest management guidelines using degree-day heat units there is an established heat unit range for each species. This range accounts for the break of dormancy, which may be egg hatch or the awakening of a caterpillar or an adult insect, and the development of that arthropod through one or several generations. GDD are expressed as a pair of numbers. For the spruce spider mite they are 7-121 GDD and account for the beginning of egg hatch through development to the adult stage of the first generation. Treatment for the spruce spider mite would be successful anytime within that GDD range; the earlier a treatment in the range, the less damage inflicted by the mite.

Remember, no pest timing system can do away with monitoring. The GDD system tells us nothing about the size of a pest population or the need for pest management action. We have used the system in these guidelines and prefer it over calendar timing, particularly for spring and early summer treatments. Each day's GDD are additive, accumulating daily throughout the growing season. The climatological calendar begins March 1 under the Cornell system, and the base or growth threshold temperature for making calculations is 50°F. This system accommodates to an early or late spring and periods of unusually warm or cool temperatures that slow or hasten insect development.

The accumulated growing degree-day numbers for the current season may not be available in your area. Every grower, arborist, and plant maintenance contractor can and should develop the system for his or her own geographical area. The formula is simple, but collecting growing degree

Table 2.6.1. Growing degree-day (GDD) table; base 50°F.¹
Maximum temperature (°F)	Minimum temperature (°F)
Maximum temperature (°F)	28	30	32	34	36	38	40	42	44	46	48	50	52	54
102	15	16	17	18	19	20	21	22	23	24	25	26	27	28
100	14	15	16	17	18	19	20	21	22	23	24	25	26	27
98	13	14	15	16	17	18	19	20	21	22	23	24	25	26
96	12	13	14	15	16	17	18	19	20	21	22	23	24	25
94	11	12	13	14	15	16	17	18	19	20	21	22	23	24
92	10	11	12	13	14	15	16	17	18	19	20	21	22	23
90	9	10	11	12	13	14	15	16	17	18	19	20	21	22
88	8	9	10	11	12	13	14	15	16	17	18	19	20	21
86	7	8	9	10	11	12	13	14	15	16	17	18	19	20
84	6	7	8	9	10	11	12	13	14	15	16	17	18	19
82	5	6	7	8	9	10	11	12	13	14	15	16	17	18
80	4	5	6	7	8	9	10	11	12	13	14	15	16	17
78	3	4	5	6	7	8	9	10	11	12

Pest Management Guidelines A Cornell Cooperative Extension Publication	Cornell Guide for Pest Management of Trees and Shrubs
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