6.1 General Guidelines
The most effective and efficient pest control programs depend on (1) diagnosis - correct identification of the insect(s) involved (i.e. who or what are the culprits behind the problem), (2) decision-making - some non-arbitrary process to decide if control is necessary (i.e. whether the situation requires a response), and (3) intervention - selecting, targeting and integrating the most appropriate control tactics (i.e. when and where to apply a control in concert with other management techniques). Navigating these steps to improved pest management also depends on how well we understand natural history, the association between the insects, the grasses they feed on, and the overall turfgrass habitat. If diagnosis, decision-making and intervention are the pillars supporting IPM, then natural history is the foundation for the entire structure.
Most of the insect pests of turfgrass conduct some stage of their life underground. This poses challenges for their management because of how difficult it is to monitor, interpret and manipulate interactions that are being played out below the soil surface. Compared to above-ground foliar feeding insects, below-ground root feeding insects are harder to sample and the products used to control them are harder to accurately deliver.
Another challenge for insect pest management is the number of exotic pests that affect turfgrass. Unintentionally introduced to the Northeast, these species have arrived without the natural enemies, competitors or other factors that might have checked populations in their native regions. Therefore they have a great capacity to outbreak and cause highly damaging infestations. Finally, pest management in turf is also challenging because there are few non-chemical control options that offer real alternatives, and because the availability of chemical options is continually changing due to phase-outs, restrictions or market-driven alterations.
In this section on insect management we give a general overview of six major insect pest complexes that affect NY State turfgrass in its many forms as home lawns, recreational areas, athletic fields, golf courses and sod farms. We will highlight aspects of their biology, ecology and behavior that are important for understanding their impact as pests and in choosing and applying the most appropriate control tactics. Because this is only a general summary, we include links to additional information on certain topics.
6.2 Insect Pests in NY State
There are some 17 insects that can cause serious injury to turfgrass in NY State and these belong to six general complexes: white grubs, weevils, chinch bugs, caterpillars, leatherjackets and ants. White grubs are scarab beetle larvae that live in the soil where they prune grass roots or otherwise disrupt the rooting zone. Weevil larvae begin as stem borers, then crown feeders, and then as adults they become foliage feeders. Chinch bugs are small, fast-moving sucking insects that live at the soil surface. Caterpillars include black cutworms that dwell in burrows at the soil surface, and fall armyworms that move aboveground as foliage feeders. Leatherjackets are the soil-dwelling larvae of crane flies that injure grass both above- and below-ground. And ants are of relevance because their nests can disrupt the surface of the ground. The injury caused by many of these insects may initially be difficult to differentiate from each other and from certain plant diseases. Nevertheless, control decisions must be based on correct identification of the insect pest, which means recognizing the injury and knowing how to identify the insect complex and insect species involved. This is important because the timing and type of control tactics will depend on the particular species, and also because chemical control products have labels specific to particular groups of insects. To be in full compliance, applicators cannot misdiagnose.
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Most damaging life stage1 |
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Group |
Common name |
Scientific name |
Name |
Habitat |
Origin |
|
White grubs |
Asiatic garden beetle |
Maladera castanea |
Grub |
Root zone |
Exotic |
|
|
Black turfgrass ataenius |
Ataenius spretulus |
Grub |
Root zone |
Native |
|
|
European chafer |
Rhizotrogus majalis |
Grub |
Root zone |
Exotic |
|
|
Green June beetle |
Cotinis nitida |
Grub |
Root zone |
Native |
|
|
Japanese beetle |
Popillia japonica |
Grub |
Root zone |
Exotic |
|
|
May and June beetles |
Phyllophaga spp. |
Grub |
Root zone |
Native |
|
|
Northern masked chafer |
Cyclocephala borealis |
Grub |
Root zone |
Native |
|
|
Oriental beetle |
Exomala orientalis |
Grub |
Root zone |
Exotic |
|
Weevils |
Annual bluegrass weevil |
Listronotus maculicollis |
Grub |
Soil surface |
Native |
|
|
Bluegrass billbug |
Sphenophorus parvulus |
Grub |
Soil surface |
Native |
|
Chinch bugs |
Hairy chinch bug |
Blissus leucopterus |
Nymph, Adult |
Soil surface |
Native |
|
Caterpillars |
Black cutworm |
Agrotis ipsilon |
Caterpillar |
Soil surface |
Native |
|
|
Fall armyworm |
Spodoptera frugiperda |
Caterpillar |
Foliar |
Native |
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Sod webworms |
Various |
Caterpillar |
Soil surface |
Native |
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Leatherjackets |
European crane flies |
Tipula paludosa, Tipula oleracea |
Maggot |
Root zone |
Exotic |
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Ants |
Mound-building ants |
Lasius neoniger, others |
Adult |
Soil surface |
Native |
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1Grub, caterpillar, nymph and maggot are terms for the immature life stage of different insect groups |
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6.2.1 White Grubs
Description. White grubs are the immature stages of scarab beetles and constitute the most diverse, widespread and damaging group of turf pests in the Northeast. In NY these include four native species (black turfgrass ataenius, green June beetle, May or June beetles, northern masked chafer) and four introduced species (Asiatic garden beetle, European chafer, Japanese beetle, Oriental beetle). This pest complex occurs throughout the state except that the green June beetle is largely limited to southeastern NY. Because of diverging habitat preferences, the most prevalent species at any one site will depend on local conditions. But as many as two to four species might occupy the same patch of turf.
Natural history. Larvae have well-developed mandibles for chewing on grass roots. While they mainly feed on fibrous roots, young larvae may ingest a high proportion of organic material. All cool season grasses are susceptible, as well as some species of forage, field and nursery crops. While the adults of some species feed and are damaging to ornamentals in their own right (e.g. Japanese beetle, Asiatic garden beetle), the adults of other species do not feed (e.g. European chafer) and none feeds directly on turfgrass.
Larvae are truly subterranean, moving horizontally through the soil to track food resources and moving vertically in response to drought and cold temperatures. Adults are generally strong fliers, mobilizing to locate mates and egg-laying sites. Because of this, many adults does not necessarily translate to many grubs. Local control of adult populations will not solve grub problems, nor will local control of grub populations solve adult problems (e.g. Japanese beetle).
Adults of most species rely on female-produced pheromones to attract males for mating. In the case of European chafer, however, males and females aggregate at dusk around prominent trees, vegetation or structures to find mates; they apparently do not use long-distance pheromones. The female lays eggs below ground, either singly or in small groups. After egg hatch, development proceeds through three larval instars, prepupa, pupa and adult.
In NY, most species complete one generation a year and overwinter as third instars. As winter approaches, larvae descend to stay below the frost line, ascending in spring as the frost line recedes. They descend once more for pupation. It is the prepupa that fashions the earthen cell in which the pupa resides until the adult emerges and crawls to the surface. Corresponding to its small size, the black turfgrass ataenius can complete two generations a year and overwinters as an adult. The inverse is true for the large May or June beetle grubs, which may require 2-3 years to complete a single generation.
Most damage is attributed to the large third instar due to extensive pruning (chewing) of the roots at the soil-thatch interface. This damage disrupts water and nutrient flow, and if accompanied by drought stress, the grass will quickly die. High populations can kill extensive areas of turf. Unlike other species, larvae of the green June beetle cause damage by their active tunneling through the root zone, not by direct feeding on roots.
Diagnosis. Larvae are “C”-shaped, with six legs, and well-developed mandibles. The eight species that occur in NY can be differentiated based on two characters of the abdomen: the raster pattern and the anal slit. The raster pattern is the specific arrangement of hairs, spines and bare patches on the ventral surface of last abdominal segment. The anal slit can be “C”-shaped or straight. With practice and the help of a hand lens, these features in third instars can be distinguished in the field. More information can be found at http://ohioline.osu.edu/hyg-fact/2000/2510.html
Heavily damaged turf peels back from the soil (often when raking) like a carpet because the root system has been disrupted or devoured. The soil surface will feel spongy, not firm, underfoot. Above ground, there will be thinning, increased susceptibility to drought and ultimately increased susceptibility to weed invasion. If grub populations do not cause visible damage, then their predators might. The grubbing activities of vertebrates like raccoons, skunks and moles can be highly problematic.
If your goal is to monitor the activity of adults in anticipation of a preventive application around the time of egg hatch, Japanese beetles can be monitored with vane traps (baited with a pheromone and floral lure), European chafer by observing mating swarms, and Asiatic garden beetle by nocturnal sweeping of the grass with an insect net or by its attraction to lights or light traps. More often, however, it is the damaging larval stage that has to be monitored in support of decision-making. To assess larvae, you have to dig. Unlike certain other turf insects, disclosing solutions will not force white grubs to the surface. Use a golf course cup cutter, bulb planter, or shovel to examine soil cores for grubs in the root zone. Depending on the size of the species, eggs and first instars are relatively difficult to find, while second and three instars are relatively easy to pick out of the soil.
Decision-making. Managers can predict damage by sampling for grubs that are still young and have not yet caused significant injury. The best time to sample is early August in southeastern NY and mid-August upstate. Egg hatch and grub development, however, may be delayed by cool or dry weather and may also vary from species to species. A sampling scheme should be based on identified problem areas, susceptible areas, and areas that otherwise require better protection (e.g. front lawns, fairways). High priority and high risk areas should be sampled more completely to reduce the chances of overlooking a damaging infestation.
Thresholds have been established as general guidelines for treatment (Table 6.2.2). If several areas are at or above the threshold, intervention may be warranted. Remember, turfgrass that receives sufficient water and has a healthy root system will tolerate higher numbers of grubs than the suggested thresholds. Extensive research in upstate NY shows that insecticide treatments are needed only 20% of the time on home lawns and golf course fairways. In other words, if the decision-making process is bypassed by the consistent use of an early season preventive insecticide, that application may have been unnecessary four times out of five.
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Number of grubs per |
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Species |
sq. ft |
core1 |
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Asiatic garden beetle |
18-20 |
2 |
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Black turfgrass ataenius |
30-50 |
3-5 |
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European chafer |
5-8 |
Any |
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Green June beetle |
5 |
Any |
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Japanese beetle |
8-10 |
Any |
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Oriental beetle |
8 |
Any |
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Northern masked chafers |
8-12 |
Any |
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May and June beetles |
3-4 |
Any |
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110.8 cm diameter soil core of the standard golf course cup cutter |
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Intervention – Cultural control. There is no specific host plant resistance among turf grasses to white grubs. Kentucky bluegrass and creeping bentgrass, however, have a spreading growth habit that is beneficial in filling in bare patches caused by grubs. In addition, endophyte-enhanced grasses (e.g. some perennial ryegrass and tall fescue) may be more tolerant of drought stress and recover more quickly from grub damage. Soil moisture and fertility affect the expression of damage by white grubs. Actively growing turf with a good root system may tolerate populations up to 50% higher than treatment thresholds without showing signs of injury. The recovery of grub-damaged turf can be hastened with fall fertilization. A high-nitrogen application in the spring, however, is detrimental because it weakens the grass by encouraging shoot development without a good root system. Counteract root loss with regular watering and counteract thinning of the stand with overseeding.
Intervention – Chemical control. There are two basic chemical approaches to managing white grubs. One is to wait until problems develop in the fall, and then spot treat with a fast-acting material like trichlorfon. The second is to make a summer application of a slow-acting and long-lasting material like imidacloprid that will prevent subsequent infestations. The dilemma is that the most easily monitored life stage, third instars, is the most tolerant to chemical controls.
The use of a preventive insecticide may be warranted in areas that consistently suffer damaging grub populations, or in risk-adverse situations with high value or high priority turf. One drawback of this approach is that applications are made too early in the season to scout for grubs. Contrary to best IPM practices, this means that thresholds cannot be assessed and that there is no nonarbitrary way to decide not to intervene with an insecticide. A second drawback is that insecticides with longer residuals will also have longer windows of exposure to nontarget fauna.
The use of a curative insecticide can be based on thresholds and a decision-making process. While these products will offer some control of large larvae, they will still be most effective if applied when grubs are less than full size and still active near the surface. Aside from the labor and cost of scouting, a main drawback of this approach is that there is usually no second chance if the application fails. Spring treatments are not recommended. At that time of year grubs are feeding vigorously between overwintering and pupation, but they are as large as they are going to get and very tolerant of insecticides. In addition, the spring flush in grass growth can usually compensate for grub damage. Regardless of approach, the goal of treatment is to reduce the population below the threshold, not to eradicate completely.
*Imidacloprid is a broad-spectrum, long-residual insecticide. This compound has become the overwhelming product of choice for white grub control in commercial turfgrass. It mostly functions as a systemic so it should be well watered in to reach the roots where it will be taken up by the plant after an activation period. The optimal time to use imidacloprid is at the time of egg laying and egg hatch. Nevertheless, its long-residual gives it a relatively forgiving window of application, from June to the first half of August. While largely used preventively, before scouting is possible, recent research shows that it may be effective against Japanese beetle as late as second instar. Because this developmental stage can be scouted, it opens opportunities to use imidacloprid as a curative. This approach might be suitable if scouting reveals an undetected and widespread infestation that is predominately second instar Japanese beetle; imidacloprid would be an option to pursue before a widespread application of a curative alternative. But unless a manager has a good understanding of the timing and potential asynchrony of population development (e.g. Japanese beetle can lay eggs over a period of more than two months), caution should prevail.
As of 2005, all commercial applications of imidacloprid products became restricted-use, statewide. In addition, the sale, use, and distribution of consumer products are no longer allowed in Nassau, Suffolk, Kings or Queens Counties.
*†Halofenozide has a similar window of opportunity, although it is most effective against the first and second instars of Japanese beetle and less effective against other grub species. It acts as an insect growth regulator that mimics the action of a natural hormone, disrupting the metamorphosis of grubs. The larvae must ingest the chemical for it to be effective and may take several days to die. The product can be applied from just before egg hatch through early grub development; once grubs reach third instar this product no longer has an effect. The manufacturer recommends application in late June or July to allow time for the chemical to penetrate the soil. It is best to minimize thatch because heavy thatch will prevent the insecticide from penetrating to the area where the insects are feeding. *†Halofenozide does not require irrigation for activation, but it is best to delay mowing until the product has been washed from the grass into the soil.
Trichlorfon is a fast-acting, short-residual insecticide recommended for curative spot treatments. Trichlorfon is highly soluble and penetrates the thatch layer better than most products. It has an extremely short period of residual activity (7-10 days) and a reduced half-life in alkaline soils. This product is recommended as a late-season curative and should be applied after the grubs have been located, up to as late as mid September.
Intervention - Biological control. Three biological control agents are commercially available for management of white grubs in turf: entomopathogenic nematodes, entomopathogenic fungi, and the bacteria that cause milky spore disease. Nevertheless, all alternatives have had poor or inconsistent results in the field. Therefore, while turfgrass managers might experiment with these products, they should not rely on them for grub management in high-priority areas. They may also be better than nothing in areas where cultural management is insufficient and chemical treatments are not allowed.
Entomopathogenic nematodes. Entomopathogenic nematodes can be effective parasites of white grubs. Although they are sometimes as effective as chemical insecticides in laboratory trials, field results have been very inconsistent and failures are common. Reasons for poor field results include insufficient water at time of application, improper selection of nematode species, improper storage and handling of the nematodes, and unsuitable environmental conditions.
Nematodes work in concert with a mutualistic bacterium that they carry in their intestines. The infective juvenile stage of nematodes lives freely in the soil; when the juveniles encounter a suitable insect host, they enter through natural openings (e.g. mouth, spiracle or anus) or are sometimes able to penetrate the insect's cuticle. Inside the host, the nematodes travel to the gut and deposit lethal bacteria that they have vectored inside. The bacteria multiply rapidly, releasing a toxin that kills the host in 1-2 days. The nematodes also multiply inside the host until resources are depleted. Eventually a new generation of infective juveniles exits the cadaver to search for a new host in the soil.
Among the currently available commercial isolates of nematodes, Heterorhabditis bacteriophora is recommended for the management of white grubs. The nematodes should be applied while grubs are still young and most susceptible and before they have caused significant damage. Follow sampling suggestions above, and apply nematodes in areas where high populations have been confirmed. Many types of pesticide sprayers can be used. Use low pressure (< 300 psi), and remove any screens finer than 50 mesh. A hose-end sprayer or watering can is ideal for small-scale applications. Apply a minimum rate of 1 billion nematodes per acre, regardless of the manufacturer’s directions.
Because nematodes are harmed by ultraviolet light, they should be applied at dusk or on a cloudy, rainy day. The nematodes use the thin film of water surrounding soil particles for movement. Therefore, irrigation (1/4 inch) after a nematode application is suggested to optimize soil conditions and to help move nematodes through the thatch. A light irrigation before the application will also reduce the chances of nematodes sticking to grass blades on the surface. Users are advised to check viability by examining nematodes for movement with a hand lens before application and again in a sample collected from sprayer output.
Fungal entomopathogens. Beauveria bassiana is a common soil-borne fungus that has been selected for its virulence to certain insect pests. When conidia attach to the insect cuticle, they germinate, penetrate with the growing hyphae, and proliferate within the insect’s body. Moist conditions favor germination, followed by infection of the insect host 1-2 days later, and ultimately death. The white appearance on the cadaver is due to the conidia produced by the mature reproductive structures of the fungus as they reemerge from the host. These infected cadavers serve as inocula for secondary spread of the pathogen in the environment.
The commercial product of Beauveria bassiana is produced through fermentation. Conidia (spores) are harvested and formulated into a sprayable liquid. Younger larvae should be targeted as being more susceptible than third instars. After application, the area should be kept wet to promote germination and subsequent infection. Speed and efficacy of the product will depend on the number of spores contacting the insect, the age and susceptibility of the grub and the environmental conditions.
Milky spore disease. Milky spore disease powder is produced by grinding up living, diseased Japanese beetle grubs infected with Paenibacillus popilliae (formerly known as Bacillus). Commercial preparations of milky spore powder are widely used for the biological control of Japanese beetle. Nevertheless, the efficacy of current formulations has not been scientifically substantiated in the field, leading to questions about the usefulness of this biological control agent for white grub management. Users must also be aware that the bacteria in formulated products have been selected for infectivity to Japanese beetle grubs and are of no value against other common grub species infesting turfgrass in NY (this host specificity is highlighted on the product label). While Asiatic garden beetle, European chafer and undoubtedly other species harbor the virus in natural populations, the commercial variety is specific to Japanese beetle. Another limitation is that because milky disease bacteria only multiply within living bodies of grubs, one must be willing to tolerate a period of relatively high grub populations to obtain disease levels sufficient to control grubs.
While scouting, you may find milky grubs that are naturally infected with local strains of bacteria. The widespread occurrence of this pathogen under natural conditions means it does have prospects for biological control of white grubs. But, this will depend on further research and development to transfer laboratory virulence into field efficacy, as well as selecting more virulent bacteria that act against more species of scarabs under broad climate conditions.
More information online:
White grub control:
http://www.nysipm.cornell.edu/publications/grubs
http://www.omafra.gov.on.ca/english/crops/facts/97-023.htm
http://www.pmra-arla.gc.ca/english/consum/whitegrubs-e.html
Japanese beetles:
http://www.omafra.gov.on.ca/english/crops/facts/92-105.htm
http://ohioline.osu.edu/hyg-fact/2000/2504.html
Asiatic garden beetle:
http://bugs.osu.edu/~bugdoc/Shetlar/factsheet/turf/Asiaticgardenbeetle.htm
http://ohioline.osu.edu/hyg-fact/2000/2500.html
Masked chafers:
http://ohioline.osu.edu/hyg-fact/2000/2505.html
Entomopathogenic nematodes:
6.2.2 Weevils
Description. The bluegrass billbug (BGB, Sphenophorus parvulus) and the annual bluegrass weevil (ABW, Listronotus maculicollis) are native weevil species. ABW is most injurious in low-cut, high maintenance turf such as golf course greens, tees and fairways. Until 20 years ago or so, outbreaks were largely limited to southeastern NY, but now the area of impact has expanded throughout New England, into Canada and south to the Mid-Atlantic. BGB is more injurious in high-cut, lower maintenance turf including home lawns, athletic fields and golf course. It impacts turf throughout the northern U.S.
Natural history. For ABW and BGB, females chew holes into the grass stem and insert eggs. Young larvae live as stem borers, chewing and consuming tissue within the relative protection of the stem and filling it up with sawdust-like frass. When they outgrow the stem, older larvae will drop down to the soil surface where they forage out to chew on surface roots and crowns. Adults feed on grass blades but cause little damage. Both species develop through five larval instars, prepupa, pupa and adult. Pupation takes place in the top layer of the soil. BGB has only one generation a year, while ABW will have two to three and maybe up to four in southeastern NY.
Adults of both species are relatively active walkers, and largely disperse on foot even though they are capable of flight. In fall, they mobilize to overwintering sites away from developmental areas. BGB adults, for instance, may settle where sidewalks meet the lawn. ABW will seek out the relative protection of tree litter and tall grass, and may be most prevalent along defined tree lines or hedgerows bordering fairways.
Diagnosis. Adults have long snouts that are the hallmark of the weevils. ABW adults measure ~3/16 in. long, about half the size of BGB (~1/4 in). In addition to overall size, ABW adults can be differentiated from BGB because their antennae arise from the tip of the snout, rather than the base, and because the hind margin of the eye is convex rather than concave. Newly emerged adults, known as “callows” or “tenerals,” are chestnut to brown in color, making the young adults distinguishable from mature adults that are dark grey to black.
Weevil larvae are legless with bodies that are straight to slightly curved. Therefore they are easily distinguished from white grubs, which have six legs and a “C”-shape. Their bodies are creamy white in color with a well-defined brown head capsule.
Injury caused by the stem boring and tunneling activities of younger larvae can be revealed through the “tug-test.” Brittle or weakened stems are easily pulled up by hand; unlike white-grub injury, the soil and root zone remain firm and not spongy. BGB damaged turf appears wilted but will not respond to watering. Damage is ultimately expressed as growing brown patches, especially near drought-prone edges such as pavement where grass may be more susceptible to heat or water stress. To distinguish BGB from drought stress, look for the frass in the form of little pockets of sawdust in the thatch or inside grass stems. BGB is most prevalent and damaging in Kentucky bluegrass. Damage will be most apparent from late June into August.
ABW injury is usually expressed as growing areas of yellow and brown spots first noticed around the collar and perimeter of the greens, tees or fairways. Early ABW damage has anthracnose-like symptoms and is frequently confused with this pathogen. Damage will be most prevalent in annual bluegrass, the favored host. It is unknown whether ABW can actually complete its life cycle on other hosts, even though it is capable of feeding on creeping bentgrass and perennial ryegrass. High populations of ABW will cause substantial areas of dead turf in highly visible and prominent areas of golf course playing surfaces.
Decision-making. In the spring, BGB adults are most active from mid May to June. It is common to see adults strolling across paved areas, in the mid to late afternoon. One way to monitor them at this time of year is with pitfall traps. Make a hole with a standard golf course cup cutter, insert a plastic cup that fills the hole and is submerged to the rim, and add an inch of water with some dish detergent. If 7-10 billbugs fall in over a 2-3 week period, injury can be expected. Another option is to observe adults walking on paved adjacent to turf in the spring. Injury can be expected if >2 are observed per minute. For the larvae, tolerance thresholds are about 8-12 per sq. ft.
ABW is challenging to monitor due to its small size. In the spring, mower baskets can be monitored for adults because they are picked up along with clippings. This can be a useful way to stay abreast of when adults are appearing in the spring, and, with more careful monitoring, on which areas of the course they are most prevalent. Some areas of the course may always harbor ABW so it is a good idea to monitor consistently those historically affected areas from year to year. Adult ABW reinvade short-mown turf soon after snow melt and soil thaw, from late March to April. A more site-specific approach to monitor adults is to pour a soapy disclosing solution on the turf. This irritant forces adults to emerge from the thatch and ascend to the surface where they can be counted. Shallow soil core sampling or simply digging around at the soil surface / thatch interface will reveal older larvae and pupae. Older larvae look like grains of rice with brown heads; pupae resemble adults but are creamy white until their color darkens before adult emergence. If more detailed information is desired, larvae of all sizes (even stem boring stages) will float to the surface when an infested core is submerged and agitated in a saturated salt solution. This is a good way to confirm that your adult controls were adequate; if too many larvae are found, the application may have been poorly timed to suppress adults and another application against adults of the developing population may be necessary.
Damage thresholds are considered to be 30-80 larvae/sq. ft for the spring generation. Given summer heat stress, thresholds drop to 10-40 larvae/sq. ft. for the summer generation. Nevertheless, field experience indicates that action may have to be taken at thresholds as low as 5-10 larvae/sq. ft in order to avoid injury and minimize the threat of the subsequent generation.
Intervention - BGB. If potentially damaging populations are detected, chemical control applications should be made between mid May and late June. This window is for targeting adults once they have emerged from overwintering sites and before they lay eggs. It is best to mow before the application and water lightly afterwards. This should prevent severe damage by larvae in July and August. If more precision is required, degree day models have been developed to optimize the timing of application.
In areas with persistent problems, host plant selection should be considered. Kentucky bluegrass is among the most susceptible cool season grass and should be avoided in favor of more tolerant alternatives. Endophytic cultivars of tall fescue and perennial ryegrass are good options because they reduce BGB survival.
Intervention - ABW. Best control is achieved by targeting early spring adult populations that represent overwintering insects returning to the short mowed turf. A preventive insecticide application is then made to suppress adult populations before the insects begin to lay eggs. The timing of spring applications can be based on a plant phenological indicator. The most widely used is the period that occurs between Forsythia full bloom and flowering dogwood full bract. It is better to make the spring application a little late than a little early so aim for the time when Forsythia is in full bloom and has already acquired many new leaves (i.e. “half gold/half green”).
Choose a relatively insoluble insecticide that stays in the thatch where adults are active. Chlorpyrifos and pyrethroids are the best options. Water in the application lightly, enough to move the material off the leaves. Widespread fairway applications are usually not necessary. It should be sufficient to limit applications to periphery sprays along historically susceptible greens, collars, tees and fairway perimeters. If this control fails, second generation adults can be targeted again sometime around July 4.
While there are products labeled for larvae, their efficacy is generally inferior to products that target adults. ABW has recently been added to the label of trichlorfon and spinosad and initial research has shown that these products may be acceptable alternatives for suppressing larvae when they are outside the stem. Otherwise, if larval thresholds are surpassed, withhold applications and monitor those areas to track development as the population matures from small to large larvae and to pupae. If sampling reveals a preponderance of pupae, delay an application for one week to effectively target the adults. No products have activity against the pupae.
In terms of cultural control, minimizing stress (e.g. due to water deficit or traffic) on annual bluegrass will help mitigate the effects of ABW. Other than that, reducing the amount of annual bluegrass is the only other option. Overwintering adults are sometimes very abundant in white pine litter, leading some golf courses to remove pine litter or even remove stands of white pine trees. Tree removal is not recommended, however, because these sites are not actually preferred locations for overwintering. Weevils will overwinter elsewhere. We may ultimately be able to define control practices based on managing adults in their overwintering habitats or by intercepting them as they return to developmental sites, but these opportunities have not yet been explored.
More information online:
Annual bluegrass weevil:
http://www.nysipm.cornell.edu/factsheets/turfgrass/default.asp
http://www.usga.org/turf/green_section_record/2003/jan_feb/annual_bluegrass_weevil.html
http://bugs.osu.edu/~bugdoc/Shetlar/factsheet/turf/AnnualblueGweevil.htm
Billbug:
http://www.ento.psu.edu/extension/factsheets/billbugsLawns.htm
http://ohioline.osu.edu/hyg-fact/2000/2502.html
http://www.uri.edu/ce/factsheets/sheets/billbug.html
6.2.3 Caterpillars
Description. Three groups of caterpillars damage turf in NY: cutworms, sod webworms and armyworms. Cutworms and armyworms largely refer to diverging habits of these moth larvae. Cutworms are solitary and tend to chew through and sever the grass stem at ground level, and then move on to the next plant. In contrast, armyworms are gregarious feeders, and tend to move across the turf eating all edible material in their paths. While there are a few species that can be injurious in turfgrass of NY, the main species of concern are the black cutworm (BCW, Agrotis ipsilon) and the fall armyworm (FAW, Spodoptera frugiperda). Sod webworms are a complex of species. Unlike the sod webworm, FAW and BCW do not usually overwinter in NY because they are too cold intolerant. Migratory adults reinvade the state every spring from populations that overwinter in more southern areas.
Sod webworms. Sod webworms are only sporadic pests and the cases are actually few where the larvae become problematic, despite the large numbers of adults that may be seen. Adults have snout-like projections on their face (commonly called “snout moths”) and have their wings folded close to the body when at rest. They are buff-colored and 0.5 - 0.75 inches long. They hide during the day. When disturbed by mowing, or at dusk, they fly in a zigzag pattern.
The larvae construct silk-lined burrows through the thatch layer and into soil. They will incorporate debris such as soil, sand and grass clippings in the tunnel walls. They forage out from burrows at night. Larvae are brown to green with darker spots and will measure 0.2 - 1 inch long. Foraging birds may indicate infestations. Habitat preferences are for sunny areas, and they can affect low to high maintenance turf (e.g. home lawns and golf course turf). Sob webworms overwinter as larvae.
Damage starts as small patches of yellowing or browning grass, or grass clipped off at ground level. Look for small piles of green frass where grass is turning brown. On low-mown turf, sod webworm damage can resemble disease, and will cause small depressed marks of brown grass that will grow in size.
The highly visible adults often concern home owners, but their presence does not indicate a pest problem. Therefore, the lawn has to be monitored for the larvae. More often than not, damage attributed to sod webworm on residential lawns is actually just drought stress—another reason it is important to scout for larvae. Scout for larvae two weeks after adult flights, when caterpillars from the new generation will be present. Caterpillars should be scouted near brown patches by spreading the grass and looking into the thatch to find the frass. Another way is to flush them to the surface using a soapy disclosing solution. The standard method is to mix 1 fluid ounce lemon-scented dish detergent in 2 gallons water and apply it over to 2-3 square feet of turf. The soap acts as an irritant, causing the larvae to emerge from hiding.
If there is enough damage and larvae to warrant control, it is best to use a less soluble insecticide such as pyrethroids that will stay in the thatch. A product should be applied as late in the day as possible (larvae are most active at night), and it should be watered in lightly, just enough to wash it off the leaves and into the thatch. Spinosad and Bt are biopesticide alternatives to conventional chemical insecticides.
Black cutworm – Natural history. BCW is common in low maintenance turf, but is particularly damaging in golf course greens and tees. Adult moths reinvade NY in spring from the southern U.S. along with spring storm fronts. This species is apparently incapable of overwintering in areas where the soil freezes. BCW will achieve 2-3 generations a year in NY. Adults will feed on flowers at night and then locate sites in the turf where they attach eggs to the tips of grass blades. Small larvae move and feed on the surface. Older larvae, however, fashion a protective burrow in the turf from which they foray to feed. These burrows lead into the soil and are the size of a pencil hole.
Black cutworm – Diagnosis and Decision-making. BCW adults are dark grey and mottled with black and brown. Larvae bear a pale stripe down the back and a greasy or oily look to them with a surface integument that is rough or pebbly. Mature larvae will get to be 1-2 inches long. Nocturnal feeding by the larvae will scalp grass around the burrow’s entrance, leaving irregular depressions that resemble ball-marks. Low-mown bentgass is particularly susceptible to damage. Foraging birds may help to indicate the presence of larvae.
The initial appearance of adults in NY can be monitored using either black light or pheromone traps set out early in the season (mid-March in southeastern NY). Both traps have limitations. Pheromone traps are relatively inexpensive and simple to maintain, but catch only male moths. While black light traps capture both male and female moths (along with a wide variety of other insects), they are expensive, require high maintenance, and are labor intensive. Because storm-driven moths are deposited randomly, there is no guarantee that lack of captures means that no females are present, nor is there any way to equate capture numbers to infestation levels; thus the usefulness of these traps is limited. A positive capture means only that chances are good that females are present and that larvae may appear within a week.
Monitoring for larvae should begin a week after the initial moth trap catches, using the soap drench method described previously. Apply the drench to 3-4 spots on the green to detect the presence of larvae. On golf course putting greens, damage may not be noticed until the larvae are quite large or have reached the fourth instar. At this point, the disclosing solution can confirm the diagnosis of cutworm damage, which superficially resembles ball marks or even dollar spot. Pest management strategies, however, should target detection and treatment of cutworms before this stage. Thresholds will vary widely from greens and tees to fairways. While the visible damage of only 3-4 large larvae on greens might require a control, turf maintained at a higher cutting height can tolerate much higher populations before thinning is apparent.
Black cutworm – Intervention. Cultural control takes advantage of the fact that BCW lays the majority of eggs on the terminal portion of leaf blades, regardless of grass mowing height. Most cutworm eggs can therefore be removed if the clippings are collected. These should be discarded at least 100 feet away from desirable turf areas to prevent return migration of the newly hatched caterpillars. Although endophytic perennial ryegrass and tall fescue are not resistant, larvae do shun feeding on Kentucky bluegrass. A 30-foot buffer of this grass around a green significantly reduces the incidence of cutworms since they are less likely to cross this barrier to settle on the greens. Another alternative is to mow greens early in the morning, between 2 and 4 a.m., when cutworms are actively feeding on the surface. Target these mowings for three consecutive nights during the early instars of each cutworm generation.
Applied every 3-4 weeks, spinosad is a potential preventive treatment. Otherwise, a range of chemistries work well for the curative control of BCW. After application, irrigation and mowing should be withheld for 12-24 hours so larvae can contact the treated foliage. Early-season detection and treatment is desirable because younger (smaller) cutworms are more susceptible than older (larger) cutworm. Higher rates might be required for the control of large larvae and for control in high-mown turf.
Bt and spinosad are biopesticide alternatives to conventional chemical insecticides. Bt is a non-living form of the bacteria Bacillus thuringiensis that is sold and labeled for management of caterpillars, including black cutworm, sod webworm and fall armyworm. This microbial toxin will also be most effective when targeting smaller and (≤1/2 in. in length) and more susceptible larvae. As with chemical treatments, mowing and irrigation should be withheld 12-24 hours.
In the area of biological control, entomopathogenic nematodes have a good chance of success in managing BCW. Use the species Steinernema carpocapsae when caterpillars are small, as with the biopesticides, and follow the recommendations described in the section under white grubs. Finally, keep in mind that a diverse array of naturally occurring enemies, such as parasitic wasps and flies, ground beetles and rove beetles, act to help suppress cutworm populations.
More information online:
Black cutworm:
http://www.ento.psu.edu/extension/factsheets/black_cutworm.htm
http://www.uri.edu/ce/factsheets/sheets/cutwormsturf.html
http://bugs.osu.edu/~bugdoc/Shetlar/factsheet/turf/Blackcutworm.htm
http://entomology.unl.edu/turfent/documnts/cutworms.htm
Fall armyworm:
http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/FallArmyworm.htm
http://www.ces.ncsu.edu/depts/ent/notes/O&T/lawn/note128/note128.html
Sod webworm:
http://www.ento.psu.edu/extension/factsheets/sodWebwormLawns.html
http://iaa.umd.edu/umturf/Insects/Sod_Webworm.html
http://ohioline.osu.edu/hyg-fact/2000/2011.html
http://www.uri.edu/ce/factsheets/sheets/sodwebworm.html
6.2.4 Chinch Bugs
Description. The hairy chinch bug (HCB, Blissus leucopterus hirtus) occurs throughout NY, west to Minnesota, south to Virginia and north to Ontario and southeast Canada. Home lawns are the most susceptible turf systems, where the insect is more prevalent in areas with thick thatch, well-drained sandy soils and full sunlight. In addition, HCB is recently being recognized as an occasional pest on golf courses where it has traditionally been of little concern to superintendents.
Natural history. HCB has piercing-sucking mouthparts that permit nymphs and adults to extract sap from the crowns and stems. This causes injury that produces drought-like symptoms. Most of the cool season grasses are susceptible to feeding. Both life stages are active and agile in the thatch and on the soil surface. HCB tends to form aggregations and this leads to patches of localized damage.
Although adults are capable of flight, they largely disperse by walking. The adults will move to overwinter in protected sites with thatch or tall grass, in debris and around structures. When they re-emerge in the spring, egg laying is preceded by a nearly 2-week preoviposition period. Up to 170 eggs per female are laid in leaf sheaths and on the ground near the base of host plants. Nymphs require 4-6 weeks to develop through five instars. One generation per year is most common in upstate NY and two generations is probably most common downstate.
Diagnosis. HCB are small, fast-moving insects. Adults are 3/16 in. long, with shiny white wings. Nymph coloration varies from red to orange to brown. If captured by hand, a pungent fruity smell may be emitted by odoriferous defensive glands on the abdomen.
The most susceptible habitats are home lawns with full sun and sandy soil where grass is less tolerant of drought stress. Abundance of the insect and severity of its injury is also favored by thick thatch. July and August are the months when the insect is most active and most damage is expressed. Their feeding causes symptoms that resemble drought stress and is often misdiagnosed as such. Unlike drought damage, lawns that are heavily damaged by HCB will not recover in the fall. Affected grass will turn yellow and then reddish-brown. Injury may be more prominent on the edges of paved areas.
Searching the soil surface should reveal the nymphs and adults. The tiniest nymphs are bright orange/red, and the adults are fast-moving, which make them relatively easy to spot despite their small size. HCB can also be detected and monitored with a flotation cylinder. Choose a spot on the fringe of a patch of damaged grass. Pound an open-ended coffee can ~2 inches into the soil, fill it with water, and look for the adults as they float to the surface. Add more water as it filters into the soil. A 5-10-minute observation should be sufficient. A variation is to cut a square of turf and submerge it in a pan filled with water.
Decision-making. If an infestation of HCB is detected, make several observations with the flotation cylinder at the margin of the affected areas. More than 20 HCB per can means that action should be taken to avoid loss of turf. Thresholds can also be made with direct visual counts. More than 10 chinch bugs found in a 60-second search of 1 sq. ft. has been used as an action threshold, as has 20-30 chinch bugs per sq. ft. in a detailed search. Make these abundance estimates at several sites around the affected area.
Intervention. Host plant selection is one form of cultural control. Heavily damaged lawns should be renovated with a more tolerant variety. Studies have shown there to be a great deal of variation in HCB susceptibility across different cool season grass species and varieties. Endophytic cultivars of tall fescues and perennial ryegrasses are good options because they are resistant to HCB. Reducing thatch buildup should also reduce the severity of infestations.
Beauveria bassiana occurs naturally as an entomopathogenic fungus that can suppress populations. Irrigation in the spring and early summer will favor this fungus and promote its activity in the natural regulation of HCB. There is also a commercial formulation of B. bassiana that could be tried as an alternative to conventional chemical insecticides.
The usual period for insecticidal control is mid summer when HCB is most active. The optimal window is after overwintered adults have stopped laying eggs and before the nymphs from their earliest eggs mature to adults. Some studies, however, indicate that overwintering adults can also be targeted in early spring before they lay eggs. Turf should be watered before any chemical treatment with 15-20 gallons water per 1000 sq. ft. Granular materials should be watered in after application.
More information online:
http://www.omafra.gov.on.ca/english/crops/facts/07-013.htm
http://www.ento.psu.edu/extension/factsheets/chinchBugs.htm