Crop and Pest Management Guidelines

2.6 Insecticides

2.6.1 Insecticide Classes and Modes of Action

Insecticides fall into chemical classes or groups such as, neonicotinoids, diamides, organophosphates, carbamates, pyrethroids, etc. For pests prone to develop insecticide-resistant populations, importance was, at one time, placed on rotating among them as one tactic to manage pesticide resistance. Sometimes materials in two different classes control pests in the same way, so now emphasis is placed on rotating among insecticides with different modes of action. To help simplify choosing among rotational partners, the Insecticide Resistance Action Committee (IRAC) has developed a Mode of Action classification system, outlined on a chart at www.irac-online.org/modes-of-action/. Most labels now include IRAC numbers representing the material's mode of action group to help users in selecting among products.

2.6.2 Phytotoxicity of Insecticides

Some plants are sensitive to certain pesticides or combinations. The label will usually name plants or incompatible pesticide tank mixes where 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. Malathion may injure certain junipers, elaeagnus, hibiscus, and some rose varieties. Avid (abamectin) has injured some Shasta daisy cultivars and should not be applied to ferns. Horticultural oil should not be tank mixed with captan fungicide. These few examples emphasize the importance of reading the label. Check Table 2.7.1 for additional information on specific products.

2.6.3 Timing Spray Applications

Pest biology and behavior 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 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.

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. 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. For more information on timing insecticide applications, see Tables 2.8.1 and 2.9.1.

2.6.3.1 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. While calendars provide a helpful approximation of timing, records of normal growth phenomena such as bud development and flowering are more useful in scheduling the proper time for treatment in any particular geographical area as they often relate more closely to the activities of pests.

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

For these reasons, using a method that is based on actual temperatures and phenological traits is considered to be a more accurate means of determining optimal times to target pests with pesticides or other management strategies. These methods are described below.

2.6.3.2 Growing Degree-Days (GDD)

GDD is an arithmetical conversion of daily temperature records to heat units to measure accumulated heat energy. 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 threshold temperature for ornamental plants in New York State is 50°F. Each day's GDD are additive, accumulating throughout the growing season.

In pest management guidelines using degree-day heat units, there is an established heat unit range for each species. This range often corresponds to the breaking of dormancy in pests, which may be egg hatch or the emergence of a caterpillar or an adult insect from an overwintering site, and the development of that arthropod through one or several generations. GDD are expressed as a pair of numbers. For the spruce spider mite, 7-121 GDD covers 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.

Monitoring is still an essential and complementary tool when using GDD. The GDD system says nothing about the size of a pest population, the need for pest management action, or even local variation. We have used the system in these guidelines and prefer it to calendar timing, particularly for spring and early summer treatments. 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. With a warming climate, there is growing discussion about using earlier start dates.

Although growing degree-day accumulations are not published in every area, each grower, arborist, or plant maintenance contractor can still use the system by collecting maximum and minimum daily temperatures (or using those from a similar nearby weather station). The formula is simple, using March 1 as a starting point and continuing daily, including weekends and holidays throughout the growing season. The daily accumulations are compared to GDD numbers for targeted pests listed in these guidelines. There are also relatively inexpensive data loggers and weather stations that collect the information automatically. Following is the procedure for calculating growing degree-days.

Regional GDD values are available on-line for some locations. For example, the Network for Environment and Weather Applications (NEWA) provides GDD daily updates for approximately 175 locations in NY (https://newa.cornell.edu/).

Formula:

Example:

2.6.3.3 Plant Phenological Indicators (PPI)

Phenology is the study of recurring biological phenomena (events) and their relationship to weather. Periodic events such as flowering occur only after a definite amount of heat energy accumulates within any given plant, as determined by its genetic inheritance. Every year that event occurs at the same "time" but not as calculated by the calendar. The same forces likewise affect the arthropod pests of any given plant. The insect and its food plant overwintering together are synchronized so well that the insect will appear at a rather precise time (i.e., egg will hatch, larva will break diapause) and be ready to feed when the host plant has what the insect needs.

To provide a readily visible plant phenological event (flowering, fruit color, seed drop) one need only observe another plant species in flower that coincides with the insect pest of concern. For example, the honeylocust plant bug will be present and vulnerable on honeylocust trees when Japanese quince begins to flower. Many other plants are in flower at the same time and they, too, may be used as phenological markers. In these guidelines we also use fruit color as a phenological indicator.

Table 2.8.1 combines the basics for three timing systems. Growing degree-days (GDD) and plant phenological indicators (PPI) systems work independently. A finely tuned GDD system and careful selection of phenological indicators complement one another. Fine-tuning is a continuous process. These predictor systems are indispensable to IPM scouting and the application of management techniques.

2.6.4 Formulations - How Insecticides Are Sold

The following concentrates are formulated for dilution with water unless otherwise instructed: wettable or soluble powders, water-dispersible granulars, emulsifiable liquids, flowable liquids, and flowable encapsulated liquids. Granules and dusts are ready for use without dilution.

The selection of one pesticide formulation over another usually is a matter of personal or economic preference. However, several factors should be considered. With few exceptions, wettable powders should not be used in mist blowers because their abrasive character causes excessive nozzle wear, requiring frequent replacement. They may be safer on plants than emulsions because more inert diluents are used in the concentrate. A visible white residue (which may be objectionable) often results from wettable powder sprays, but usually not from emulsions. Adding a wetting agent or spreader-sticker to wettable powders may be desirable, especially on hard-to-wet foliage. During treatment, continuous agitation in the sprayer tank is essential.

Emulsifiable concentrates should be selected for long-lasting residual deposits; they are resistant to washing off. Some organic solvents used to dissolve the active ingredient may cause plant injury. Be cautious; when in doubt, spray small areas on a trial basis before treating an entire field or planting. Never use broken emulsions (spray mixtures that show oiliness on the surface). A good emulsion spray concentrate mixed with water will have a uniform milky color.

Liquid concentrates are amenable to the microencapsulation process. Encapsulation may change a nonresidual material into one that has residual effectiveness (e.g., pyrethrum). Mammalian toxicity may also be reduced.

Granules are used primarily for application to soil. Dusts are seldom used for commercial applications.

Spray combinations are often a convenient and economical way to combine two or more pesticides in one spray application to control a number of pests such as insects, mites, and disease-causing organisms. Such combinations reduce labor and machinery costs. Some pesticides, such as horticultural mineral oil, may provide a synergistic effect that improves efficacy. Often several pests are present at the same time, and two or more different selective pesticides may be necessary to provide control. Unless otherwise stated on the label, dilution rates do not change when combining pesticides under New York State regulations. Compatibility of pesticides in a spray dilution must be determined from labels or a compatibility chart. The use of certain spray adjuvants may be desirable. Generally, avoid tank mix combinations of chlorothalonil or copper-based fungicides with all other pesticides or adjuvants unless otherwise indicated.

2.6.5 Systemic Insecticides

Systemic insecticides are chemicals that can be applied to plants via the soil, leaves, or bark, or injected into the vascular system to control insects and mites as they feed on the host plant. They translocate (move) through the plant and usually concentrate in the most rapidly growing parts. Systemics are advantageous because they (1) reduce the area of contamination, (2) are often effective longer than other classes of pesticides, (3) can be applied under certain circumstances when the seasonal workload is lighter, (4) reduce contact with beneficial insects, and (5) are less subject to decomposition by sunlight and weather.

Some systemics are highly toxic chemicals and should be used with extreme caution and only by highly experienced workers. There may be a lower margin of tolerance between effective control of the pest and serious injury to the plant. They may cause foliage "burn" on certain plants. Plant species, soil type, rainfall and moisture availability, type of insect pest, and cultural practices are some of the factors that influence effectiveness of systemic insecticides. Some systemics can impact pollinators through movement into pollen and nectar. Label updates are now including more specific pollinator protection language and application restrictions.

Systemics are available in granular, powder, tablet, and liquid concentrate formulations. Granules can be broadcast, used as side-dressing, or placed in various kinds of plant containers. Other formulations can be sprayed on foliage or bark or injected into soil or into tree trunks and buttress roots.

Some insecticides, though not true systemics, have "translaminar" activity, meaning that they penetrate into leaf tissue after foliar application and have a localized effect but do not actually move to untreated areas of the plant. Abamectin (Avid and generics) and pyriproxyfen (Distance, Fulcrum) have good translaminar activity applied to tender foliage, a key to enabling long residual control. Other translaminar insecticides and miticides include etoxazole (*TetraSan), pymetrozine (Endeavor, Devenir), acetamiprid (*TriStar, *Quasar), imidacloprid (*Merit, *Marathon) and spinosad (Conserve, Entrust). Adjuvants such as horticultural oil or wetting agents sometimes enhance leaf penetration while stickers may impede it. Penetration into hardened-off or mature leaf tissue may be relatively poor compared with that for tender young growth.

2.6.5.1 Systemic Injection Techniques

TreeTech Microinjection, Acecap, Arborjet, Wedgle, M3 Infuser, and Mauget are registered trademark companies, products or technologies dealing with the application of systemic pesticides to trees. The Acecap system uses a pesticide implant; Arborjet, M3 Infusers, TreeTech Microinjection and Mauget are injection systems that use external pressure to force "medication" into the vascular system. These techniques require that holes be drilled into the trunk or buttress roots. The implant method is simple to perform. The injection system requires more attention to details but has some technical advantages in smaller drill holes and faster effectiveness. The Wedgle system uses a needle applicator to inject insecticide between the bark and outer sapwood.

Our experience is primarily with the Mauget system. Properly executed treatments in the spring or early summer will kill a wide range of leaf-chewing and sapsucking insects, including gall formers. Results may be spectacular. Flatheaded borers such as the bronze birch borer have been reported to be controlled, whereas control of bark-based, phloem-feeding homopterans such as scale insects is erratic at best. Continuing problems limit these systems and preclude general guidelines for them. Obtaining consistent, complete systemic distribution into the crown of a tree, where large branches may not receive the toxicant, has been a problem. Poor distribution is, of course, common with other application techniques, but these are often attributed to human error. Poor systemic distribution relates more to structural variability in the vascular system of trees than to human error. It has also been reported that repeat applications (third and fourth treatments) give progressively poorer pest control. We do not generally recommend annual treatments to the same tree. Discolored wood and decay are often found at old injection sites.

All systems are highly useful where spray treatments are objectionable or operationally difficult and some effective treatments (like emamectin benzoate for emerald ash borer) are only available for trunk injection. Internal "medication" systems have a respected role in the application of systemic insecticides.

Mechanical tools are available for injecting systemic insecticides into soil around roots. Most of the feeder roots of any plant are within the top 4 inches of soil, that part of the soil profile where the insecticide will have the best chance of uptake. Instructions for use are provided by the manufacturer.

2.6.6 Imidacloprid Insecticides: Best Management Practices for Soil Application

Imidacloprid, a neonicotinoid insecticide and active ingredient in *Merit, *Marathon, *Discus, and many other insecticides, demonstrates the properties and characteristics associated with chemicals detected in groundwater. The use of this chemical in areas where soils are permeable, particularly where the water table is shallow, may result in groundwater contamination. All commercial and professional imidacloprid products are restricted use in New York State and soil injection uses are not permitted on Long Island (Nassau and Suffolk Counties), where there have been low-level detections of imidacloprid in subsurface water. To help protect pollinators from exposure, use on all Tilia (linden, basswood) species are now prohibited. Labels also include special pollinator-protection restrictions. All home garden imidacloprid products are also prohibited in Nassau and Suffolk Counties. As of January 1, 2023, imidacloprid insecticides that are foliar applied or have widespread oudoor use were classified as restricted use in NY, limiting use to certified applicators. Products used to treat ground around trees were not affected by the classification change. Judicious use is essential if applicators are to continue using imidacloprid in the future. Users should consider alternatives, then take special precautions before deciding to apply any material and when applications are made. Check with your local Cornell Cooperative Extension (cce.cornell.edu/ localoffices), New York State DEC office (dec.ny.gov/ about/contact-us/statewide-office-information) or dealer for more detailed information on Best Management Practices when applying these materials. Best Management Practice guides for imidacloprid are posted online at cesuffolk.org/agriculture under "BMPs to Protect Groundwater". Above all, read label directions carefully and use as directed.

The following suggestions can help minimize the risk of groundwater contamination and off-site movement of imidacloprid when using it in professional landscape situations or in nurseries especially for soil application:

Identify the pest or problem first. Insect pests, plant disease and/or other factors sometimes cause similar symptoms but are treated differently. For example, potato leafhopper injury might be mistaken for fertilizer or herbicide damage. Be sure of the actual cause and the presence or threat of the target pest before applying the insecticide.

Is the pest a serious threat? Some pests are of minor concern in certain situations and treatment may not be needed. For example, bean aphid on euonymus and spirea aphid on crabapple cause a foliar distortion that is not a threat to the health of the plant. Both tend to be spring problems, disappearing as foliage hardens off in early summer.

Incorporate cultural or other non-chemical controls. For example, avoid applications of nitrogen to adelgid-infested hemlocks, maintain good watering and fertilizer practices, prune off infested terminals (e.g. bean aphid on euonymus, Nantucket pine tip moth on pines, viburnum leaf beetle egg sites on viburnum), dislodge scales on bark and aphids on foliage with a blast of water, and use mulch around landscape plants to reduce bark damage.

Use pest-resistant plants where possible, considering plant species less likely to need imidacloprid applications for key pests. For new installations, examples include river birch as an alternative to borer-prone European birch, leafminer-resistant boxwoods, or other conifers as alternatives to hemlock woolly adelgid-susceptible Canada hemlock. A list of resistant plant species and varieties is available through the NYS IPM Program (cals.cornell.edu/new-york-state-integrated-pest-management/outreach-education/ipm-areas/ornamental-ipm).

Consider alternative insecticides or formulations where available and effective. While imidacloprid has been important in a few situations and for certain pests, some insects are easily controlled with other labeled products that do not have properties associated with risk of movement to surface or groundwater.

Use appropriate application equipment for granular formulations. In outdoor landscapes, use of drop spreaders or shielded broadcast spreaders may be best along impervious surfaces (sidewalks, roads, other paved areas) and near drains to help keep granules on target.

Calibrate and maintain application equipment to be sure granular delivery or drench applications are accurate for the area or pot size treated. When applying to individual pots, be sure drenches are of appropriate volume and use careful irrigation practices to avoid leaching insecticide from treated pots. Avoid application when heavy rain expected. Application equipment should be in good working condition without leaks. Mix and load in a handling facility or away from where spills and runoff can contaminate groundwater.

Time applications for best results. For potted plants, apply to soil or media only when plants are well-rooted, established, and likely to take up material in the early stage of spring growth. For most landscape tree and shrub pests, spring or possibly fall application seems to be the best in general although there are some exceptions.

Apply where plant roots can take up material. It is suggested that soil drenches be applied to allow movement into the upper 6 inches of soil only. Usually, applications are made around the base of the tree or within a short distance (1 to 3 feet) of trunk or stems.

Consider using minimum label application rates. Highest label rates may not be necessary. Labels include a rate range for soil treatment; lower rates can be used for some pests like aphids and adelgids, or for emerald ash borer when applying in spring rather than fall. Lower-than-label rates are permitted by New York State law only for agricultural production, when not otherwise prohibited by the label. In all other situations, lower-than-label rates are not allowed unless approved by the New York DEC.

Use foliar or bark application or trunk injection instead of soil treatments, which may be sufficiently effective and pose less risk of movement to groundwater (imidacloprid breaks down quickly in sunlight) compared with soil treatments. Drench treatments quickly reach the label-listed maximum amounts that can be applied per acre per season, particularly in nursery settings. Foliar sprays provide less residual control than systemic treatments, but are faster to act. For example, a spray may be favored over a drench for aphid-infested potted plants nearing the end of production in a nursery situation or for hemlock woolly adelgid where coverage is expected to be good. Addition of adjuvants (spreader/stickers) may be necessary with sprays to improve control on waxy foliage or against insects such as adelgids or melon aphid.

Do not make soil applications under certain conditions. Watch weather forecasts and avoid use within 72 hours of an expected heavy rain. Applications should also not be made where there is a shallow water table, when soil is frozen or waterlogged, or directly to water or to intertidal areas. Labels note a possibly shorter period of protection when applied to media containing 30% or more bark.

Limit the number of applications. When using soil applications, one treatment per season should suffice. Experience indicates that adequate protection may even last into a second year in some cases. Preventive applications are not always needed.

Store and handle concentrated material carefully. Packages and containers can be placed inside secondary containment such as plastic bins to reduce chances of spillage.

Clean up spills promptly and dispose of properly. Sweep insecticide granules off hardscape areas such as sidewalks and do not allow material to wash into storm drains, recharge basins or similar areas where there is high risk of leaching to groundwater or for runoff to streams, bays or other surface waters. Scoop up contaminated soil and treat as hazardous waste.

Keep good application records, including target pest(s) and weather conditions at application and within 24 hours of application as well as other information as required by law.

2.6.7 Oil Sprays

Mineral horticultural spray oils (superior type oils) are currently recommended for both dormant and summer pest control treatments. These oils originate from petroleum refining companies and meet certain refining standards. All horticultural oils will have a minimum UR (unsulfonated residue) standard of 92 percent; products available range from 92 to 99 percent hydrocarbon purity. This refining process removes most of the impurities such as nitrogen, sulfur, and chlorine and replaces them with hydrogen. The gravity or density standard in part is a measure of the paraffinic content of the oil. The minimum gravity on the Baume scale is 30°F with a range of 30°F to 35°F; the higher the number the better. Paraffinic oil with a high UR reacts slowly if at all with other chemicals in contrast with petroleum solvents and fuels, and herein lies the matter of phytosafety. See Table 2.6.1.

During refinement, the temperature of the second distillation determines the range of final product uses. A narrow distillation temperature range, from about 400°F to 435°F, yields horticultural oil suitable for application to green, verdant plants. Distillation temperatures above 435°F produce oils suitable for use on plants only in a dormant condition. Only certain oils are suitable for application to plants under summer growing conditions; these are identified in Table 2.7.1. Summer-use oils generally include dormant-stage directions as well, usually with a higher application rate. The same oil (e.g. Sunspray 6E) may be sold by different companies under various brand names and is sometimes marketed for year-round (summer and dormant) use in one package or only for dormant stage application in another. In a few cases, oil in the container may even come from different refiners in different years; price determines source. Check labels carefully to see if summer uses are permitted. For "green industry" users, a "summer" oil is often the more useful oil product because it can be used in dormant applications by increasing the dosage. One oil tested under a great variety of summer conditions has the trade name Ultra-fine (Tables 2.6.2, 2.7.1). It can be used on fruits, vegetables, flowering annuals, foliage plants, trees, and shrubs, and in both field-grown and greenhouse conditions with a wide range of pesticide efficacy targeting major species of plant-feeding mites, aphids, adelgids, psyllids, lace bugs, certain leafhoppers, mealybugs, scales, whiteflies, certain plant bugs, and thrips. Chewing insects, primarily those in immature stages (caterpillars, leaf beetles, and sawflies), are also killed. Horticultural oil is also effective against some powdery mildews.

Horticultural mineral oils have been extraordinary pest management tools, especially for IPM systems. In addition to having low acute toxicity for humans, the dilute oil spray generally presents low exposure risk to mammals, birds, and most other vertebrates. It is highly lethal to a wide range of insects and mites on contact, however, with good compatibility for insect parasites and predators. Timing of summer oil sprays to protect active adult parasites may require adjusting the spray date as little as one day. Direct spray contact with predatory beetles such as adult lady beetles appears to have no deleterious effect.

Oils are most useful as summer sprays. Oils developed for summer use are as safe to plants as most of the synthetic organic insecticides. Research conducted on the verdant oils is finding additional uses in terms of the range of insects and mites controlled. Up to four applications of oil may be made safely during the growing season.

Some caution is advised concerning safety of oils to plants. Risk of plant injury may be increased when oil is combined
with certain other pesticides (e.g., chlorothalonil (Daconil, Bravo, Manicure), dimethoate, carbaryl, sulfur; see labels for others). Oil should not be applied during periods of high temperature, humidity, and/or drought stress. Although a wide variety of plants have been evaluated, certain plants may be sensitive, and some labels suggest using lower rates or testing first on Cryptomeria (Japanese cryptomeria), Cotinus (smoke tree), Chamaecyparis (falsecypress), juniper, Ilex crenata (Japanese holly), and spruce. Eastern redcedar (Juniperus virginiana) and Douglas fir (Pseudotsuga menziesii) may be sensitive, as is walnut (Juglans spp.) foliage. If very young foliage is present, lower label rates are suggested. Avoid using oil at frequent intervals, at excessive rates, and when there is risk of freezing within a day or two of application. Oil application causes blue, glaucous foliage to turn green. New, unsprayed growth will again have the blue coloration.

There is limited information on safety of fall dormant applications. In our trials, October applications of 3 percent oil to conifers led to injury that appeared later in winter or in early spring. Although some arborists have applied oil in November to deciduous trees without damage, some labels advise using lower rates and applying the oil only to certain species. Until research provides clearer guidelines, it is suggested that early spring dormant applications are a better choice than fall dormant applications.

Oil synergizes some of the organic pesticides and has been shown to enhance penetration through the waxy layer of cuticle on a leaf. Such features are particularly advantageous when using such systemic insecticides or fungicides. Oil reportedly increases surface residues of insecticides and therefore their efficiency by countering volatility, protecting against sunlight degradation, and retarding removal by rainfall. When used alone or in combination, oil also acts as an antidesiccant, improving the plant's ability to conserve moisture, a feature very important in seasons of drought.

As presently understood, oil sprays must be used on a high-volume basis. If a target pest feeds on both surfaces of a leaf, the spray must wet both sides. To reach the under-surface of leaves, it is more efficient to start spraying inside the tree canopy and work out. Anything less than complete coverage may result in poor control. Other mechanics of the spray operation are also different. Under summer conditions, water-miscible oil will separate quickly if the hose lines are left idle for as little as 15 minutes, especially when fully exposed to the heat of pavement and direct sunlight. When the spraying is resumed after such a delay, globules of pure oil will strike the target plant with the potential for severe phytotoxic reaction. It is best to habitually run all of the spray fluid from the hose back into the tank for agitation after any delay.

2.6.8 Storing Pesticides

Pesticides left unused after the growing season can pose a storage problem. Ideally you should only purchase the amount of pesticide you intend to use. However, if you need to store pesticides, consult the product label for storage and shelf-life information. Manufacturers are another good resource for this information. When storing pesticides, keep them in their original containers with the original labels intact and tightly sealed. Storage conditions for several pesticides are noted in Table 2.10.1.

2.6.9 Pesticide Adjuvants

Adjuvants, broadly defined, are chemicals that improve the performance of pesticides. Adjuvants, broadly defined, are chemicals that improve the performance of pesticides and fall into several categories. Activator adjuvants include such products as non-ionic surfactants ('surface-active agents') for enhancing wetting on waxy or glossy surfaces and plant uptake or improving adhesion and resisting wash-off (spreader-stickers), and organosilicone surfactants which provide for more extreme wetting and surface tension reduction for greater uptake or penetration into plants. Oil-type adjuvants include materials based on petroleum oil, combination products with petroleum oil and a non-ionic surfactant (NIS), and methylated seed oil derived from vegetable oil and formulated with a NIS. Special-purpose adjuvants are available to adjust water pH and hardness (conditioners), reduce foaming (defoamers), stabilize mixtures (keep materials from separating or for reducing UV light degradation), or add baits or other chemicals attractive or disruptive to insect pests.

Adjuvants are increasingly important in today's pest management systems, especially as IPM specialists customize programs for plant maintenance contractors and growers. Adjuvants may reduce labor costs by making one spray operation do the work of two or three such adding a compatibility agent to allow pesticides and liquid fertilizers to be mixed in the same tank. Research has shown some cases of improved control of pests with addition of surfactants to spray mixtures: oil, for example, enhances substrate penetration of some pesticides like abamectin, providing better residual activity; it may also act as a spreader by allowing the mixture to "creep" under leaf hairs (trichomes) and flaky bark to provide better coverage. Oil may also act as a needed filter for ultraviolet light when certain microbial pesticides are used. (See 2.6.7 Oil Sprays.)

Adjuvants may even provide incidental pesticidal activity on their own, though may not be labeled or registered for such use. Adjuvants including horticultural oil can increase risk of phytotoxicity and should not be included with some pesticides such as chlorothalonil or sulfur. Before using a new product or mixture, conduct a small-scale test it to verify that it presents no risk of phytotoxicity to valuable plants. See Table 2.7.1 and labels for specific information.

Conditioners or buffers are used to adjust the pH of water, especially where a pesticide is degradable in highly alkaline or acidic waters. In New York State local water sources vary considerably in pH and dissolved minerals that can interfere with performance of pesticides. Water especially from deep wells or from municipal sources may contain enough dissolved calcium and magnesium to make the water highly alkaline or interact with materials such as insecticidal soap or bifenazate. Each water source should be checked for pH and adjusted with a conditioner according to the physical properties of the pesticide. (See Table 2.6.2.)

2.6.10 Mist Blowers: Limitations of Low-Volume Spray Equipment

Nursery and Christmas tree growers, commercial arborists, and foresters have found mist blowers to be an efficient method for applying pesticides to shade trees and shrubs, especially in areas where high gallonage spraying is impractical or impossible. Large mist blowers can treat plants rapidly and thoroughly with practically no runoff, however drift may be an issue due to the small droplets used. Portable backpack blowers are sometimes used on smaller trees and shrubs.

The principles of low-volume spraying are important and need to be thoroughly understood. Mist blowers move concentrated insecticide to the plant by means of a high-volume, high-velocity airstream. The insecticide is diluted largely in the airstream rather than in water, as with high-gallonage hydraulic applications. Four factors are critical in mist spraying: (1) the concentration of the spray in the tank, (2) flow rate at the nozzle, (3) length of time a tree or group of plants is sprayed, and (4) thorough, even coverage of the plants.

Spray particle sizes are measured in micrometers. These particles are made up of active ingredient, solvent for the active ingredient, adjuvants, and water. In the airstream, they are subject to rapid evaporation. Under low relative humidity, spray particles 100 feet from the nozzle may lose liquidity and become a solid insecticide particle. As such they would adhere to a substrate only if the substrate was sticky and the particles' velocity enough to cause them to impinge. To reduce evaporation, formulations may be modified with oil or solutions containing sugar, but this rarely gives a mist blower an effective range greater than 100 linear feet. Spraying with mist blowers is more complex than hydraulic spraying and requires highly skilled, careful operators. Serious plant injury can result when high-velocity spray particles rupture the foliage or from excessive pesticide application (overspraying). A mist blower is not suitable for use as a hydraulic sprayer. See Table 2.6.3 for pesticide mixing instructions. Dilution rates are very different for mist blower spraying, although the objective is to apply the same amount of actual pesticide to a given area as in hydraulic spraying. Be sure to check labels for any restrictive wording concerning low- volume application. Some labels specifically prohibit such use. Most labels specify application rates on a per-100-gallon
basis; more concentrated sprays may be considered a violation unless specifically noted on the label.

Concentrated sprays applied in highly dispersed mist droplets do a poor job of controlling sluggish, slow-moving, or immobile sucking insects (scales, aphids, mealybugs, lace bugs) or mites. Mist blower equipment can be used to control such pests if spraying is modified by using a more dilute spray mix, increasing the particle size and output rate, and increasing the spray time per tree to provide adequate coverage. By definition, this is not a true mist blower operation but rather a compromise between low- and high-gallonage applications.

Mist blowing is most effective under windless conditions, which often occur at night, early morning, or evening at twilight. The most weather-appropriate time is from midnight until morning. Mist blowers equipped with spotlights are very effective for night spraying. Drift is a particular concern with low-volume sprayers and may present problems for other non-target species such as pollinators or grazing animals. Because it is difficult, if not impossible, to control spray drift even with light winds, legal responsibility and environmental stewardship may preclude uses of mist blowers in urban areas, near bodies of water or where there is risk of exposure to non-target species.

2.5 Biorational Pest Management Tools and Tactics

2.7 Insects and Mites Destructive to Woody Ornamentals