Systemic insecticide for trees

Systemic Pesticides: Chemicals You Can’t Wash Off

When the Pesticide Action Network reviewed the results of pesticide residue tests conducted by the U.S. Department of Agriculture from 1999 to 2007, numerous samples contained residues of these systemic pesticides. For example, 74 percent of conventionally grown fresh lettuce and 70 percent of broccoli samples showed imidacloprid residues. Clothianidin was found in potatoes, thiamethoxam showed up in strawberries and sweet peppers, and some collard green samples were laced with dinotefuran.

The U.S. Environmental Protection Agency (EPA) has launched a comprehensive review of the environmental safety of imidacloprid, but we won’t have results until 2014! In the meantime, the state of California initiated its own reevaluation (currently ongoing) of all four systemics in February 2009. Among its reasons, California’s Department of Pesticide Regulation cited reports of eucalyptus nectar and pollen with imidacloprid levels up to 550 parts per billion — nearly three times the 185 parts per billion needed to kill honeybees. And deadly levels of these systemic poisons are even showing up in leaf guttation drops (water droplets that plants sometimes exude). According to a 2009 report in the Journal of Economic Entomology, “When bees consume guttation drops, collected from plants grown from neonicotinoid-coated seeds, they encounter death within a few minutes.”

Equally disturbing, it appears that nitroguanidine pesticides can persist in soil for 500 days or more, which creates a high risk scenario. After one or two applications, plants grown in treated soil may produce toxic pollen, nectar, and guttation droplets for more than two seasons. All the while, the entire treated area will be moderately toxic to beneficial earthworms, carabid beetles, lady beetles, predatory pirate bugs and more.

There is no scientific evidence yet that says food laced with neonicotinoids will harm humans, but why is the EPA allowing systemic pesticides on food plants in the first place? Do people really want to eat pumpkins that are so full of poison that they kill every cucumber beetle that dares take a bite? Looking beyond food plants, does the use of systemic pesticides to grow perfect roses justify the deaths of millions of bees and other insects? We need to set things right and learn (once again) this important lesson: When we let a novel, man-made chemical loose in the food chain, we can’t be entirely certain of what will happen next. This new contamination of our food is yet another reason to grow and buy organic.

Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.

‘Systemic’ Pesticides Poison Every Pore of Your Plants

Q. Mike: Applying systemic chemical pesticides is a nuisance, and the products can be so dangerous that ORTHO has taken its systemic pesticides off the market. I have tried using products like Pyola, Neem Oil, etc. but they don’t seem to have an effective residual presence on plants like my roses. Gardens Alive and other natural gardening catalogs feature a vast array of pesticide and fungicide products. My Question: Which ones kill on contact, and have good residual effectiveness? Last summer I used a combination of natural and Ortho products every 7 – 10 days. Is there a better method?

    —Frank in North Andover, Mass.

A. Let’s begin with some definitions. The word “pesticide” refers to any substance used to control something undesirable, including insects, slugs and snails, rodents, weeds, and disease. So insecticides, molluskicides, rodentacides, herbicides and fungicides are all grouped under the ‘pesticide’ umbrella.

And despite what many people believe, the word pesticide does not automatically mean the control is a chemical. Pesticides can be natural/organic products or toxic man-made chemicals. That’s right—if it’s sold for use against a pest, it has to be called a pesticide, regardless of whether it’s a natural soil organism like one of the Bt’s or a persistent, deadly chemical like DDT.

‘Contact pesticides’, like insecticidal soap and horticultural oils, must actually strike a pest to harm it. If you spray soap or oil on a pest, the pest will be smothered and die. Spray soap or oil on a leaf in advance of a pest being there, and you waste your time and money. (And run the risk of being mocked by the pest when it does show up.)

Most pesticides are ‘residual’; that is, they cling to the surface of a plant and remain active for a certain amount of time. BTK—an organically approved naturally occurring soil organism that’s deadly to caterpillar pests—is a good example. You spray it on a plant being eaten by caterpillars and the caterpillars currently feeding on the sprayed leaves die, and so do any new ones that show up to feed for a while. How long that ‘while’ lasts depends on variables like temperature, rain, and sunlight.

‘Systemic’ pesticides are taken up inside the plant, typically through the root system, so that every part of the plant then contains the chemical. (I say ‘chemical’ here because I can’t think of any organic systemics.) As you can imagine, systemics on food crops are an especially bad idea. In fact, in one of their very first uses, the string beans they were “protecting” became as poisonous to people as the attacking bean beetles.

Now, you specifically mention roses, and we don’t eat our roses (that’s what Japanese beetles are for), so what could be the problem with systemic pesticides there? Jay Feldman, long-time Executive Director of the great watchdog group Beyond Pesticides, in Washington, DC didn’t have to think about the question more than an instant.

“Merit is the most widely used systemic pesticide”, he explained, “and the active ingredient in Merit is the chemical most implicated by researchers in the Colony Collapse Disorder decimating honeybee hives around the world. Growers use Merit to protect their plants, bees ingest the chemical when they collect pollen from those plants, and boom—the bees are poisoned because the chemical is in every part of the plant, including the pollen. And this isn’t specific to just Merit; its just one example of how these types of pesticides can have a profound and deadly impact on non-target organisms like pollinators.”

And of course, without pollinators, we got no food or flowers.

You also speak of having to treat your plants every week to ten days. That’s a huge red flag. If you’re using ANY pesticide—chemical or organic—that often, something is badly out of whack in your garden.

If disease is the problem you’re battling, are your roses getting morning sun and good airflow? Do you have wood, bark or other disease-harboring mulch incubating illness underneath your plants instead of a mulch of disease-preventing compost? Do you invite even more disease by wetting the leaves of your plants when you water?

If aphids—a common ‘target pest’ of systemics—are the issue, have you tried blasting them off the plants with sharp streams of water? Researchers found this ‘mechanical technique’ to be as effective as any pesticide against aphids—and it won’t foster disease if you do it first thing in the morning, when the sun can dry the plants off immediately afterwards. Aphids are also well controlled with insecticidal soaps, light horticultural oils and/or boric acid traps at the base of the plants if ants are ‘farming’ and protecting the aphids so they can dine on the sweet honeydew the aphids excrete.

And finally, are you feeding your plants harsh chemical fertilizers? The fast, weak unnatural growth these chemicals cause makes plants much more attractive to pests and prone to disease.

Switch to compost, practice good sanitation and prevention, and watch your problems shrink and your plants prosper. Because in the end, a natural feeding program based on improving the health and life of your soil is the most reliable ‘systemic’ response to virtually any problem.

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Colorado State University

Print this fact sheet

by W.S. Cranshaw * (6/13)

Quick Facts…

  • Many houseplant insect problems are introduced by infested plants.
  • Carefully check plants before purchasing and quarantine them in a separate area for a few weeks to avoid introducing new pest problems.
  • Changes in cultural practices can help control many houseplant insects, such as fungus gnats.
  • Several insecticides are available to control houseplant pests. For some pests, biological controls also exist.

Houseplants are susceptible to attack by many insects and mite pests. Some of these houseplant pests can cause extensive damage to the appearance and health of the plant while others are simply a nuisance. Plants that are not vigorously growing and/or are under stress may be particularly susceptible to insect and mite injuries.

Infestations of scale insects (mealybugs and whiteflies) are almost always established from infested plants recently purchased or received as gifts. As a precaution, all new plants should not be placed with existing houseplants for at least three weeks. A careful inspection at the end of this time helps determine the presence or absence of pests.

Methods Used to Control Houseplant Pests

Syringing plants. Many household plant pests can be controlled, at least in part, by washing the plant periodically with a vigorous jet of water. This is particularly effective for spider mites and aphids, which are most readily dislodged.

Cultural changes. Watering affects houseplant pests in a couple of differerent of ways. Excessively moist soil favors the development of problems with fungus gnats. However, plants placed in very hot, dry sites are prone to problems with spider mites.

Handpicking. Larger houseplant insects can be controlled by handpicking. This is especially useful for scale insects and mealybugs. Regularly using small, hand-held vacuums assist in controlling whiteflies.

Trapping. Yellow sticky traps can be useful to reduce the number of insect pests that fly – whiteflies, winged aphids, and fungus gnats. These traps are sold commercially or you can easily make them by cutting bright yellow cardboard and covering it with petroleum jelly or some other sticky material. However, trapping alone will not entirely eliminate problems because much of the population, including the younger stages, remain on or about the plants.

Sanitation. Seriously infested plants are often best discarded because they usually require lengthy and extraordinary efforts to control the pests. They may also serve as a source for infesting other plants. You can use periodic “host-free” intervals to cause insects that survive for short periods without feeding to die out.

Biological controls. Under certain conditions, natural enemies of houseplant pests are effective in reducing the problem to acceptable levels. However, they are relatively difficult to acquire and are usually available only through specialty suppliers. See Table 1 for a list of several biological controls for pests associated with houseplants.

Table 1. Summary of biological controls for insects and mites affecting houseplants and interiorscapes.
Species Pest(s) controlled
Predator mites Spider mites Several species of predator mites are available that feed on spider mites. Check with a supplier as to the species best adapted to the environment of the plantings. Predator mites are quite perishable.
Whitefly parasites (Encarsia formosa, Eretmocerus californicus) Whiteflies Can effectively manage greenhouse whitefly if temperatures are maintained at an average of at least 72 to 75 degrees F. Inefficient at lower temperatures. Available through several mail order suppliers.
Mealybug destroyer (Cryptolaemus montrouzieri) Some mealybugs A species of lady beetle that feeds solely on young and eggs of mealybugs. This species has been used successfully in some indoor plantings but requires fairly high mealybug populations to maintain. Most effective in warm temperature settings. Available through several mail order suppliers.
Mealybug parasite (Leptomastix dactylopii) Mealybugs Has provided control of mealybugs in atrium settings. Available through some mail order suppliers.
Aphid predator midge (Aphidoletes aphidimyza) Aphids Larvae are predators of aphids. These have been most effective at higher temperatures. During winter supplemental lighting must be provided to maintain a minimum of 12 hours daylight or they become dormant.
Green lacewings Aphids, primarily A general predator that feeds on a wide variety of insects and may help suppress mealybugs, scales and spider mites. Widely available from garden catalogs, often as eggs.

Alcohol. Sprays of alcohol, or alcohol dabbed onto insects, is well known as a useful control of mealybugs. However, using alcohol on plants may cause injuries such as leaf burn. Carefully test a small part of the plant if you attempt to use this method.

Insecticidal soaps. Insecticidal soaps (potassium salts of fatty acids) are one of the most commonly available houseplant insecticides. These are used as dilute sprays (one to three percent concentration) and can help control many houseplant insects and spider mites. Many liquid hand soaps and dishwashing detergents also have insecticidal effects, although there is potential for plant injury with such treatments. See fact sheet 5.547, Insect Control: Soaps and Detergents for more information.

Horticultural oils. Diluted sprays of oils (petroleum distillates, mineral oils) are some of the most useful insecticides for houseplant pests, capable of controlling scales, young whiteflies and spider mites. These are highly refined oils that primarily act by smothering. See fact sheet 5.569, Insect Control: Horticultural Oils for more information.

Neem. Some houseplant insecticides are derived from seed extracts of the neem plant, a commonly grown tree in many tropical areas. Neem seed contains materials that disrupt insect growth and is useful for control on developing whiteflies and some other insects. Neem seed also contains oils that may be used in a manner similar to other horticultural oils and is sold in products labelled as containing “clarified hydrophobic extracts of neem seed.”

Pyrethrins and pyrethroid insecticides. Pyrethins are a common ingredient in many houseplant and garden insecticides. They are a natural product derived from flowers of a certain (pyrethrum) daisy. Pyrethrins are fast acting, have a very short persistence (a few hours), and low toxicity.

Several “synthetic pyrethrins,” better known as pyrethroids, are also commonly used. These are synthetically manufactured insecticides based on the chemistry of the natural pyrethrins. Some of these pyrethroids, such as resmethrin and sumithrin, are also fast acting and have a short persistence like the natural product. However, other pyrethroids, such as permethrin, cyfluthrin, and bifenthrin, may persist in active form on foliage for several days. Pyrethroids may have differences in their ability to control houseplant pests, such as bifenthrin, which is much more effective than other pyrethroids against spider mites.

Systemic insecticides. Some insecticides, known as “systemic insecticides” have the ability to be absorbed by plants. Those used on houseplants are sold as granules or as stakes. They are applied to the soil for the roots to absorb.

Bacillus thuringiensis var. israelensis (H-14 strain). A naturally occurring soil bacteria, Bacillus thuringiensis, has the ability to control many insects. It is a commonly used microbial insecticide. Different strains of this bacteria occur which may have different effects on insects. For example, one strain (“kurstaki”) is commonly sold to control caterpillars on vegetables and ornamental plants. Another strain, “israelensis” or “H-14,” can control certain larvae of gnats, blackflies, and mosquitoes. It is sold under the trade names Gnatrol and Knock-Out Gnats to control fungus gnat larvae in houseplants.

Notes on using pesticides:

Follow the cautions listed below when using pesticides on houseplants to avoid exposure and plant injury.

1. Only use pesticides that are specifically labeled for use on houseplants. Most yard and garden pesticides do not allow this use.

2. If possible, take the plant outdoors before spraying to minimize pesticide exposure within the home.

3. When using aerosol sprays, do not apply closer than 18 inches to the plant or injury may occur from the spray. This precaution appears on most label use directions.

4. Avoid treating plants that suffer from environmental stresses such as temperature extremes or drought to minimize potential plant injury.

5. If granules or plant stakes containing DiSyston are used, use extra care when watering. Excess water may carry this insecticide as it puddles or drips. This product is extremely toxic.

6. Always read and follow instructions on the label!

Common Houseplant Pests

Figure 1. Greenhouse whitefly adult and nymphs.

Figure 2. Greenhouse whitefly adults.

Greenhouse Whitefly

Greenhouse whitefly (Trialeurodes vaporariorum) is a common pest of several houseplants such as poinsettia, ivy, Hibiscus, and Lantana. Greenhouse-grown vegetables, such as tomatoes and cucumbers, are also frequently infested. Damage is caused from the insects sucking sap from the plant. Heavily infested plants may drop leaves prematurely and have reduced vigor. During feeding, whiteflies also excrete sticky honeydew that detracts from the appearance of the plant.

Winged adults are the stage most commonly seen. They are somewhat gnat-like and covered with fine white wax. Adults lay eggs on the leaves. These eggs hatch in three to seven days to produce the immature nymph stage. Most feeding injury to the plant occurs by the nymphs. Whitefly nymphs are scale-like in shape, translucent color, and fairly immobile. Feeding on the leaf undersides, whitefly nymphs are often inconspicuous and easily overlooked. After feeding for two to four weeks, whitefly nymphs change into an inactive “pupal” stage. This stage typically lasts one to two weeks, before adults emerge. Adults may be active and lay eggs for two months if conditions are favorable.

The greenhouse whitefly is a tropical insect that is incapable of overwintering outdoors in Colorado. Freezing temperatures or a relatively short host-free period eliminates greenhouse whitefly. Although most houseplant problems originate from the purchase and movement of infested plants, some whiteflies can reproduce and infest new plantings during the warm summer months.

Management. Yellow sticky cards or tape can be used to trap adult whiteflies. On small plants, adult whiteflies can be eliminated by vacuuming.

Insecticides containing pyrethrins or related insecticides (tetramethrin, resmethrin, sumithrin) are the most effective chemical controls for adult whiteflies. Horticultural oils, neem insecticides, and insecticidal soaps may control nymphs on leaves. The systemic insecticide imidacloprid is highly effective against greenhouse whitefly.


Figure 3. Citrus mealybugs on coleus.

Mealybugs are soft-bodied insects that suck sap from plants. This weakens the plant and causes leaves to shed. Mealybugs also excrete large amounts of sticky honeydew. Coleus, cactus, lantana, hoya, jade, and poinsettia are among the plants mealybugs prefer. Root-infesting mealybugs are associated with African violet and gardenias.

When full grown, most female mealybugs produce a large amount of cottony material in order to lay hundreds of eggs. The eggs hatch within a few days. The newly emerged insects, known as crawlers, move about the plant. Oftentimes, infestation of new plants occur during this movement. Mealybugs mature in apporximately two months.

Mealybugs may infest different areas of the plant. Although populations on foliage are most visible, most mealybugs infest roots and some are predominantly associated with roots. Some species tend to move to roots when growing conditions are less favorable, but return in high populations on stems and leaves when plants are actively growing.

Management. Swabbing individual mealybugs with alcohol is useful for control. Dilute alcohol sprays (25 to 50 percent concentration) or insecticidal soaps can also be used. However, before applying these treatments be sure to test a small area because some plants may become injured. Alcohol and soaps are strictly contact sprays with no residual action. Root-feeding stages of mealybugs will be missed with these treatments.

Sprays of pyrethroid insecticides (tetramethrin, bifenthrin, permethrin) are usually effective for mealybug control. The soil-applied systemic insecticides disulfoton and imidacloprid can also be effective.

Biological controls for mealybugs include a species of ladybird beetle (the “mealybug destroyer,” Cryptolaemus montrouzeri) and a type of parasitic wasp (Leptomastix dactylopii). However these are expensive and difficult to use effectively which limits their application primarily to large indoor plantings where using insecticides
is not desirable or possible.

Spider Mites

Figure 4. Twospotted spider mite and eggs.

Figure 5. Spider mite webbing on Norfolk Island pine.

The twospotted spider mite (Tetranychus urticae) is one of the most common houseplant pests. Unlike whiteflies and mealybugs, the twospotted spider mite can survive year-round outdoors in Colorado, going dormant during the winter. Original infestations of houseplants may arise from plants kept outdoors, from mite migration from outdoor plants, or
by acquiring infested plants from a greenhouse. Once established on a plant, spider mites can crawl short distances or be carried or blown to other plants.

Spider mites feed on plant sap, producing small wounds on the outer plant cells which appear as white flecks. In the beginning of a spider mite infestation, these injuries occur as small patches on the leaf underside near the base of leaf veins. As damage progresses, the leaves have a generalized “off” color that appear as a graying or bronzing. Spider mites also make webbing and in very high populations the webbing may be very visible. Often heavily infested leaves drop prematurely. Common hosts include ivies, dracaenas, figs, hibiscus, Norfolk Island pine, and scheffleras.

Spider mites have a short life cycle that can be completed in one to two weeks under favorable conditions. Approximately five eggs may be laid daily by a mature female. Eggs hatch within a couple of days and the newly emerged nymphs feed almost continuously.

Management. Spider mite control can be difficult. Heavily infested plants should be disposed of whenever possible since they serve as a source of new infestations. Fundamentally important is providing optimal growing conditions as spider mite problems can be aggravated by a poor environment.

The most effective controls include washing and increasing humidity around the plant. Small plants can be repeatedly washed with a jet of water from a shower or kitchen sprayer. This forces off the mites and eggs. If done over the course of several weeks, mite populations should be reduced to low levels.

Twospotted spider mite is difficult to control with pesticides. Horticultural oils are probably the most effective spray. Bifenthrin, found in many houseplant insecticide preparations, can also be effective for spider mite control. Insecticidal soaps are marginally effective.

In large indoor plantings, using predator mites may be considered. Several species of predator mites are available and can be used successfully to manage mites on greenhouse grown tomatoes, cucumbers, and some ornamental plants.

Other Mites

Figure 6. Cyclamen mite damage to African violet. (Photo by J. Baker.)

Much less commonly found are the cyclamen mite and the broad mite (Family Tarsonemidae). Both are extremely tiny and do not make the webbing characteristic of spider mites. Instead, the presence of these mites is usually suspected from the plant symptoms that they produce. Cyclamen mite often cause new growth to be stunted, twisted, and sometimes killed back. Leaves may also appear small, thick, and rough textured. African violet is the houseplant most often damaged by cyclamen mite. Broad mite produces a bronzing of the leaf underside on plants such as citrus and begonias.

Management. Cyclamen mites can be very difficult to control since they occur deep within leaf folds and other protected sites. Therefore, it is usually recommended that cyclamen mite-infested plants be discarded.

Soft Scales

Figure 7. Brown soft scale.

Figure 8. Honeydew produced by brown soft scale.

Several scales, particularly the brown soft scale (Coccus hesperidum) and the hemispherical scale (Saissetia coffeae) may attack houseplants. These occur on many kinds of plants but problems are most frequent on ficus, citrus, ferns, and ivies. Heavy infestations of soft scales result in large amounts of sticky honeydew which can create serious nuisance problems. Sustained infestations can cause die back.

The brown soft scale is found on both twigs and leaves. Eggs hatch underneath the cover of the mother scale continuously over a period of several weeks. The newly hatched “crawlers” have limited mobility and usually move short distances in search of feeding sites. After the scale crawlers settle to feed, they begin to produce the characteristic protective body covering and excrete honeydew as waste. The scales continue to grow over the next two to four months rarely moving in later stages.

Management. Soft scales can be difficult to control since their protective covering largely prevents contact insecticides from being effective. However, spray oils are the most effective treatments for scales. Alcohol and soap sprays may also provide some control of scales, particularly crawler and very young, poorly protected stages.

Where infestations are not widespread, scales can be killed by rubbing or picking them off. Fairly minor disturbance of the settled scale can break its mouthparts, causing it to starve. Scales killed in this manner, or by soaps or oils, may remain in place and appear similar to living scales.

Crawler stages are susceptible to most houseplant insecticides. However, insecticides must maintain coverage throughout an entire generation of the insect (two to four months) to eliminate further infestation. Short persisting insecticides, such as pyrethrins and resmethrin, need reapplying at least once per week. Longer persisting treatments, such as bifenthrin and permethrin are effective for scale control when used at longer intervals. Soil applied systemic insecticide imidacloprid should be effective for most soft scale infestations.

Armored Scales

Figure 9. Armored scales. (Photo by J. Capinera.)

Armored scales are much less common than soft scales. Typical species are generally round in shape, often with a distinct central spot. Many cause spotting around the feeding site. They can also cause die back when abundant. Unlike soft scales, they do not produce honeydew and, except for a very brief period after egg hatch (crawler stage), are immobile. Horticultural oils are the most effective treatment for armored scales. Systemic insecticides provide poor control.


Aphids develop as pests on several types of houseplants including ornamental peppers, hibiscus, chrysanthemums, and many garden plants and herbs. Aphids also feed on plant sap and excrete large amounts of sticky honeydew. In high populations they cause wilting and distortions of the new growth.

Aphids common on house plants include the green peach aphid, potato aphid, cotton/melon aphid, and chrysanthemum aphid. Populations increase rapidly as generations can be completed in two to three weeks.

Figure 10. Chrysanthemum aphids.

Management. Since aphids are exposed on the plant, periodic washing with water and contact sprays of insecticides is effective. However, most aphids adapted to greenhouse culture, particularly the green peach aphid, are highly resistant to insecticides due to long-term exposure. Imidacloprid is particularly effective for aphids. Insecticidal soaps and pyrethroid insecticides may also be effective.

Biological controls for aphids have had modest success at best. Some aphids are best controlled by a small predator midge, Cecidomyiia aphidomyza. Mass releases of green lacewing eggs, which hatch into larvae that prey on aphids and many other insects, can also be effective.


Thrips are extremely minute insects, usually less than 1/16 inch when full-grown. They have elongated bodies and are usually brown, although pale and dark forms can be common. Adults can fly and their very small size allows them to easily penetrate most screening.

Figure 11. Thrips and associated damage.

Figure 12. Thrips scarring of flowers. (Photo by J. Capinera.)

Thrips are usually recognized by the damage they cause. Light, irregular silvery areas on the leaf surface develop around the feeding site. Tiny dark spots of excrement appear at the feeding area. This feeding may somewhat resemble spider mites, but wounds produced by thrips are larger and more silvery. Thrips infesting buds and developing flowers produce distortion and scarring of petals.

Perhaps most important is the ability of thrips to transmit certain virus diseases to plants. Tomato spotted wilt is a very serious disease, primarily affecting vegetables but also many ornamental plants. The closely related virus impatiens necrotic spot similarly has a very wide host range, particularly among ornamental plants. See fact sheet 2.947, Greenhouse Plant Viruses (TSWV-INSV) for more information on this serious disease.

Management. Many strains are resistant to insecticides and their habits make them even harder to control. Egg stages are inserted into plant parts and later immature stages (sometimes called “pupae” and “prepupae”) develop in soil where they are inaccessible to sprays.

Pyrethroid insecticides control some thrips (onion thrips) but not the most common types. Exposed stages are controlled with soaps or oils. Adults are attracted to sticky traps, particularly yellow or pale blue.

Where problems with tomato spotted wilt or impatiens necrotic spot occur it is critical to remove and destroy all infected plants immediately since they can serve as a renewing reservoir of the disease.

Fungus Gnats

Figure 13. Fungus gnat adult.

Figure 14. Fungus gnat larve.

Fungus gnats (Bradysia species) are small, dark colored flies that jump and fly across the soil surface. Adult gnats are commonly seen as they collect around windows. Fungus gnats cause little or no injury to house plants but create a serious nuisance problem. Problems are most common during winter and early spring. Since these insects develop in potting soil, virtually any houseplant can be a host for fungus gnats.

Adults live for a few days and lay eggs in soil cracks and around the base of plants. The pale colored larval (“maggot”) stage feeds on fungi and decaying organic matter. They also feed on root hairs of the plant which causes reduced plant vigor. A generation can be completed in one month.

Management. Fungus gnats are native insects and are common in lawns and garden soils. Reinfestation from these outdoor sources is very likely and difficult to prevent completely. However, fungus gnat populations can be reduced to levels that are not a serious nuisance. Since fungus gnat larvae feed primarily on decaying plant materials, changing soil moisture conditions is the most important step to take. Watering should be limited so that the soil surface can dry between waterings.

Some adults can be captured on sticky cards. However, as they are very short lived they may have laid many eggs before capture. Adults can also be suppressed by sprays of pyrethrins and pyrethroid insecticides. However frequent application is required to reduce adult abundance and egg laying, particularly when using insecticides of short persistence.

Larval control is more effective. The biological insecticide Bacillus thuringiensis var. israelensis or (H-14 strain) is highly effective as a soil drench. Also some neem products are labeled for soil drench purposes and can control fungus gnat larvae. Unfortunately neither of these products is commonly sold in Colorado and may be more readily acquired via mail order.

Other Flies

Figure 15. Shore flies and associated “fly specks.”

Sometimes other flies are associated with indoor greenhouses. Where algae develops shore flies may become established. These flies are slightly larger than fungus gnats and don’t pose nuisance problems. However, adults regurgitate dark material and “fly specks” on plants. In stagnant water rich in organic matter moth flies can breed. These minute flies have a broad feathery wing that superficially resembles a small moth. Both shore flies and fungus gnats are managed by eliminating breeding sites.


Figure 16. Springtails.

Springtails are small, gray or cream-colored insects that feed on decaying organic matter in soil. They are most often recognized by the habit of many species to jump on the soil surface, like a small flea. They are most often observed in potted plants shortly after watering brings them to the surface. Springtails cause little, if any damage to houseplants but can be a nuisance problem. Limiting water reduces springtail numbers.

Table 2. Summary of cultural and mechanical controls for houseplant insects and mites.
Pest Non-chemical Controls
Spider mites Increase humidity around the plant; periodically hose with jet of water.
Greenhouse whitefly Use sticky traps to capture the adult whiteflies; vacuum plants to capture adult stages.
Brown soft scale Physically pick or rub scales to kill them; coat individual scales with alcohol.
Mealybug Coat individual mealybugs with alcohol; grow plants under conditions that allow moderate growth to reduce succulence favored by many mealybugs.
Fungus gnats, Springtails Avoid excessive watering; avoid use of high organic matter soils or fish emulsion fertilizers which can favor development of fungi eaten by fungus gnats.
Aphids Periodically hose the plant with a vigorous jet of water. Crush individual aphids. Yellow sticky traps may capture winged adults.
Table 3. Summary of expected performance of insecticides available for use on houseplants.
Insecticide Whitefly nymphs/ adults Mealy bugs Spider mites Soft scale Armored scale Aphids Fungus gnat (larvae/ adults)
Horticultural oil C/N S C C C S N/N Primarily acts by smothering; no residual effects.
Insecticidal soap S/N S S S* S* C/S N/N Contact insecticide with no residual effects.
Pyrethrins, resmethrin, sumithrin, tetramethrin N/S S S/N S* S* S/N N/C Short persistence (hours).
Permethrin, cyfluthrin S/C S N S* S* S/N N/C Moderately persistent (days) pyrethroids.
Bifenthrin S/C C C/S S* S* S/N N/C Moderate persistent pyrethroid with some activity against spider mites.
Neem insecticides C/N N N N N S C/N Acts to disrupt growth of some developing insects.
Neem oil C/N S S S S S N/N A plant-derived horticultural oil.
Disulfoton S/S S S S N S N/N A systemic insecticide applied to soil. Highly toxic.
Imidacloprid C/C C N C S S N/N A systemic insecticide usually applied to soil; some foliar treatments are available for houseplants.
Bacillus thuringiensis var. israelensis (H-14) N/N N N N N N C/N A bacterial disease of certain fly and gnat larvae.
C – Can provide control of the pest; S – May suppress numbers of the pest; N – Not effective for control of the pest.* Effective against the newly hatched, crawler stages of scales only.

*W.S. Cranshaw, Colorado State University Extension entomologist and professor, bioagricultural sciences and pest management. Reviewed 11/06.

Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.

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‘Tis the season for houseplant pests: how to keep them at bay

Now that winter is here, scale insects have started showing up on my potted citrus tree and some orchids. How many other plant pests lurk, ready for a population explosion when conditions become ripe, typically in late winter?

Dowsing plants – especially indoor houseplants – with pesticides is bothersome and hazardous. Repeat applications usually are needed to catch each wave of the emerging pest population at its most susceptible stage. And it’s difficult to spray a plant thoroughly while keeping the mist off curtains, windows and furniture. A number of sprays can stain or even dissolve certain finishes or plastics.

A systemic pesticide such as Bonide Systemic Insecticide Granules, which spreads within the plant, also has shortcomings. It creates a toxic plant, which can poison any pet or child who nibbles a leaf. And, such materials can’t, of course, be used on an indoor citrus whose fruit you plan to eat.

Story continues below advertisement In this undated photo, Cottony cushion scale insects are enjoying their feast on this plant\’s leaves in New Paltz, New York. AP Photo/Lee Reich

Indoors, where rain and wind can’t carry away residues, you have to be wary even of pesticides labelled “natural.” Natural does not mean nontoxic. Rotenone, for example, is an all-natural pesticide extracted from a tropical plant, yet it is much more toxic than, say, malathion, a synthetic pesticide that also might be used on houseplants. I’m not suggesting using synthetic pesticides over natural ones on houseplants, but be aware of the hazards associated with any pesticide.

I try to avoid using pesticides altogether. They are just one approach to controlling pests, and should be the last one. Other approaches may demand greater intimacy with your pests, learning their habits and life cycles, but that’s part of what makes gardening interesting. Books such as The Gardener’s Guide to Common-Sense Pest Control by William and Helga Olkowski, and The Organic Gardener’s Handbook of Natural Pest and Disease Control, edited by Fern Marshall Bradley, Barbara W. Ellis and Deborah Martin, detail ways to control many houseplant pests.

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For now, I’m dealing with scale insects by flicking any that I see off leaves with my thumbnail. I know I won’t eliminate them with this brute-force method, but I can at least keep the population in check. In a couple of months, they might get ahead of me, but by then perhaps the ladybugs that call my home their home will help out, as they have in years past.

I’ve used similar methods against aphids, crushing them where they congregate on leaves near the tips of stems, and against mealybugs, doing them in with a cotton swab dipped in alcohol. Keeping an aphid-infested plant in the shower will wash the pests away and create conditions inimical to another common pest, red spider mites, which are hard to see but make their presence known by imparting a bronze cast to leaves.

Trapping is a more elegant approach to pest control. Thwart aphids on single- or few-stemmed plants by blocking travel of the ants that herd and protect them: Wrap a sticky band around the stem or stems. Masking tape coated with sticky Tangle-Trap works and lasts for weeks. If clouds of whiteflies puff up whenever you brush against your geraniums, place yellow cards coated with oil or Tangle-Trap near the plants.

Good growing conditions also can help deter pests. Less frequent watering, for instance, is usually all that’s needed to deal with fungus gnats or sowbugs.

Yes, the occasional pest-ridden houseplant will need the last resort, a pesticide spray (or a walk to the compost pile, always an option). Even then, there are some effective and relatively nontoxic sprays, such as insecticidal soap, horticultural oil and Bt. By the time a spray is needed, the weather likely will have warmed enough that it can be done outdoors. Hold pests at bay long enough and you can move houseplants outdoors for their summer vacation, where pest problems frequently clear up by themselves.

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What is a systemic insecticide?

If you’ve gardened for a while, chances are that you’ve heard the term systemic insecticide. When applied to pesticides, the term systemic means that the chemical is soluble enough in water that it can be absorbed by a plant and moved around in its tissues. Movement of systemic insecticides, like all transportable chemicals in the plant, takes place principally in the plant’s vascular system, which includes the phloem and xylem.

Not all chemical compounds are soluble in water. Most chemicals are going to soluble in water to some degree, or soluble in oil to some degree. Solubility is not an either/or thing. Some pesticides are highly soluble in water, some moderately so. Most pesticides have relatively low solubility in water.

What are the pros and cons of a pesticide being highly soluble in water? On the down side, being highly soluble in water means that a pesticide is more likely to be washed off of a plant by rain or irrigation. Also, high water solubility means that a pesticide may be more easily washed into a stream or (especially in places with sandy soils) seep into ground water. On the plus side, water soluble pesticides may be absorbed more easily into a plant, since plants are largely made of water and the sap is mostly water.

Pesticides that can be applied to the soil beneath a plant and transported in the xylem sap tissue can reach pests that are otherwise hard to kill. Many sap feeding insects, like scales, don’t move around much and may be protected by wax, or by the plant itself, from insecticides sprayed on the leaves and stems. These insects do take in lots of plant sap during feeding, however, so a pesticide in the sap can be easily ingested by the pest.

When systemic pesticides are applied to the soil, beneficial insects, birds and even pets and people are much less likely to encounter the pesticide in the form of residues or spray drift. The treatment of some trees (for example the big oak over the swimming pool) would be difficult to do safely without a systemic pesticide option.

Some of the common house and garden insecticides that are systemic include acephate (Orthene®), imidacloprid (Bayer’s Tree & Shrub Insect Control™, Merit®) and dinotefuran (Greenlight Tree and Shrub Insect Control™, Safari®). You should be especially careful when using systemics if you have a shallow water table under sandy soils, or if you are applying the product near streams, lakes or water features. As with all pesticides, it is important to read and follow the label of a systemic pesticide carefully at the time of purchase, before use, and before discarding any leftover containers or product.

What is systemic insecticide

Whether you are just starting with gardening or have already been a gardener for many years I am sure you have come across the term systemic insecticide, because it is quite commonly used to describe insecticide, so it is important to understand what it means.

Insecticides usually are classified in two groups, first being contact insecticides that have no residual activity and the second being systemic insecticides that have residual or long term activity. Here it is again the word systemic and this time combined with the word long term.

So what it all means?

The easiest way how to explain what systemic insecticide does is to understand how it works. If contact insecticides kill the insects upon their contact with the plant that is sprayed with this insecticide, hence the name contact insecticide, then systemic insecticide works a bit slower but also very efficient – the systemic insecticide becomes incorporated throughout the whole plant usually in a protein form that is not toxic to humans or animals and then when the targeted insect feeds on this plant, they ingest the insecticide and die. And if contact insecticide will wear off with the wind or rain, because it sits on top of the plants, then systemic insecticide will stay in the plant and will work for quite some time.

The plants are able to absorb the systemic insecticide into their cells and move it around thanks to the fact that this insecticide consists of substances that are highly soluble in water, so that plants can soak up the insecticide just like they would do with water. The downside is that if you apply the insecticide just moments before it starts to rain, there is a good chance that the insecticide will be washed away by the rain because it is water like or if the insecticide is applied incorrectly it can flow down from the plant and into the ground, however if there is no rain and the insecticide is applied correctly then the insecticide will be easily absorbed by plants.

There are some systemic insecticides that are applied to the soil not the plants, however, I wouldn’t recommend them because by doing it this way there is a bigger chance that not only your target insects will ingest this insecticide and be killed but it will be ingested by beneficial insects and even birds that can harm them.

Usually that how efficient each of these insecticides are is determined from that how the insecticide is sprayed. For example if a fogger is used in the application then the results will be much better, because the insecticide droplets will be very small and will thoroughly cover targeted area, but if a sprayer is used that distributes the solution in large droplets, then all targeted plants might not be coated with the insecticide you are using.

Systemic insecticide is one type of insecticide that you should really consider especially if you need to target places that are near other objects that cannot be laced with this insecticide, for example, if you want to spray the flowers that are near the pool with an insecticide, you cannot use contact insecticide, because that can contaminate the pool, however by using systemic insecticide it will be safe to enjoy your pool without having to worry about insects pursuing your flowers.


PRODUCT DESCRIPTION: Odorless material which is applied to the soil around plants, trees and shrubs which works as a systemic. This formulation is safe for use in the garden and can be used on both fruit and vegetable bearing plants.

WHERE TO USE IT: Outside the home in the yard for any plant, flower, shrub or tree.

RATE OF APPLICATION: Mixtures vary depending on the size of area you want to treat and whether you’re treating leafy vegetables/fruits or trees.

For most ground growing vegetables and fruits, 1/2 oz per quart of water per 10 sq/ft is sufficient with “days to harvest” in the 7-14 days range.

For broadcasting out over the plant foliage, mix 1 oz per gallon of water for every 50 sq/ft. The quart will cover up to 1600 sq/ft.

For fruit bearing trees, the rate will vary based on tree size; you’ll need to read the label for specific rates or call for help in calculating.

TARGET PESTS: Adelgids, Aphids, Armyworms, Japanese beetles, Lace bugs, Leaf beetles (including elm and viburnum leaf beetles), Leafhoppers (including glassy- winged sharpshooter), Mealybugs, Psyllids, Sawfly Larvae, Thrips (suppression) and Whiteflies to name just a few.



$30.00 32 oz (.235%)(455260)(FREE STANDARD SHIPPING)
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(Last Updated On: June 7, 2010)

Photo courtesy Educational Community Garden, Urban Solutions Center, Dallas.

It’s not often that I dislike seeing a new pesticide label. Not that I like insecticides per se (they are tools for pest control), but in recent years new insecticides have generally represented products that produced either better or safer control of pests. The active ingredient, imidacloprid, in the new Bayer Advanced™ Fruit, Citrus and Vegetable Insect Control is not new, but the label is. The recent label amendment permits imidacloprid use by homeowners on fruit and nut trees, citrus, herbs and vegetables.

Imidacloprid is a systemic insecticide, which means that it is water soluble enough to be picked up by plant roots and translocated throughout the plant via the vascular (sap) system. This is not true of most insecticides, which tend to have very low water solubility and mostly stay where they are put. But systemic action can be a good thing, making application easier (especially on big plants, like trees) and even safer for beneficials (no residues on leaves to harm predators and parasites). I believe imidacloprid is one of the better products we use for safely controlling white grubs, aphids and other sap-feeding insects on ornamental plants.

The use of imidacloprid for commercial vegetable production is not new. Years ago the manufacturer of imidacloprid had to do a lot of homework to get a vegetable label. Any pesticide manufacturer who wants to label one of their products for use on food crops has a very rigorous set of standards that must be passed. First the government has to issue a tolerance–that is a level of the pesticide that it deems is safe for human consumption. These tolerances are carefully vetted by toxicological research. Then research must be done to find out how long a grower must wait after application before the pesticide has degraded to that safe, tolerance level. This is called a pre-harvest interval. When you read on a pesticide label that you should wait 3 days until harvest, that’s the pre-harvest interval. This interval is designed to make sure you are not eating dangerously high levels of pesticides.

I’ve always told Master Gardeners, and others who asked, that systemic insecticides are generally not labeled for edible crops because they can persist in plant tissues. This persistence has been noted repeatedly for imidacloprid by researchers, with insect control persisting up to a year or more on some woody plants. Presumably the persistence of imidacloprid in vegetables is shorter, and the levels of product remaining at harvest low enough to pose any human health risks. The new Bayer label has a pre-harvest interval of 14-21 days. The label also specifies that no more than one application should be made per year. These sorts of restrictions on a product are required by EPA to ensure that levels remaining on the plants are below acceptable residue tolerances.

My dislike of the new label is not necessarily because I distrust the science. The EPA generally does a good job reviewing toxicology data and environmental fate data. I am concerned, however, that homeowners are less likely to read and follow the small print on a label than a commercial grower with pesticide applicator training.

In my experience, home gardeners tend to be more emotionally sensitive to pesticide use in their own garden, even if they don’t always buy their veggies from the organic produce section at the store. This comes, it seems to me, from an expectation that food from our own gardens should be purer and more wholesome that store-bought foods. I know this is the way I feel about my garden.

I am reluctant to water imidacloprid into my veggies when insecticidal soap or oil might be just as good and less risky. My personal list of acceptable insecticides in the veggie garden includes soap and oil, spinosad and Bt products, hard streams of water, and maybe even an occasional use of a spot application of a pyrethroid insecticide on tough pests like squash bug. But even though my brain says trust the science, my heart says leave the systemic products for lawns, trees and shrubs. If you choose to do otherwise, be sure to follow the pre-harvest interval.

What Is A Systemic Pesticide: Using Systemic Insecticides In Gardens

If you have ever heard the term “systemic pesticide,” you may have wondered what it means. This is actually an important thing to know to prevent accidental hazards in the garden. It’s also important to know how to use a systemic insecticide should such use be warranted.

What is a Systemic Pesticide?

A systemic pesticide is any pesticide that is absorbed into a plant and distributed throughout its tissues, reaching the plant’s stem, leaves, roots, and any fruits or flowers. Systemic pesticides are water-soluble, so they easily move throughout a plant as it absorbs water and transports it to its tissues.

Typically, these chemicals are applied to soil and taken up through plants’ roots; less commonly, they are applied to foliage or injected into tree trunks.

Systemic insecticides are specifically those that target insects. Some of the most commonly used systemic insecticides are neonicotinoids. These are a group of insecticides that interfere with insect nervous systems.

Systemic herbicides (weed killers), fungicides (which target fungi), and nematicides (nematode killers) are also in use.

Are Systemic Pesticides Safe?

Systemic insecticides cannot be washed off a plant after they are absorbed, since they are inside the plant’s tissues, including the parts we eat as fruits or vegetables. Because systemic pesticides are water-soluble, they can easily be washed away from the application site if it rains before plants absorb them. Then they can run off into a neighboring body of water or natural area.

One group of systemic insecticides, the neonicotinoids, is suspected of poisoning honeybees and other beneficial insects: these chemicals enter the pollen that bees collect, and they can be found in nectar as well. It is very important for applicators to understand how to use a systemic insecticide properly and to take measures to protect pollinators and other non-target species.

In some cases, a systemic pesticide is safer for the environment than a non-systemic pesticide would be. For example, systemic insecticides used for tree pest control, including the emerald ash borer, are injected into the trunk or applied to the soil for uptake by the tree’s roots. Less of the chemical ends up drifting onto other plants or contacting non-target insects than if non-systemic chemicals were sprayed.

Also, systemic chemicals are more effective in targeting certain pests, which may allow for less frequent applications or lower volumes than would be required with a non-systemic pesticide.

However, non-chemical pest control methods are usually the safest. These include integrated pest management (IPM) strategies and many of the strategies developed for organic farming and gardening. Non-chemical strategies are a better choice for protecting pollinators and other beneficial insects.

Systemic Insecticides in Gardens

Most common insecticides used in home gardens are non-systemic. Most systemics are only approved for use in commercial agriculture or horticulture, while some need to be applied by professionally trained pesticide applicators. Recently, systemic insecticide products have become available for sale to home gardeners in some locations.

Extra care is required when using systemic pesticides in a home garden, especially on vegetables and fruits, and it’s best to choose another pest control strategy if possible. If you do use one of these products, be sure to use it only on plants for which it is approved. When using systemic insecticides, it is essential to follow the label instructions regarding when and how to apply.

If you’ve gardened for a while, chances are that you’ve heard the term systemic insecticide. When applied to pesticides, the term systemic means that the chemical is soluble enough in water that it can be absorbed by a plant and moved around in its tissues. Movement of systemic insecticides, like all transportable chemicals in the plant, takes place principally in the plant’s vascular system, which includes the phloem and xylem.

Not all chemical compounds are soluble in water. Most chemicals are going to soluble in water to some degree, or soluble in oil to some degree. Solubility is not an either/or thing. Some pesticides are highly soluble in water, some moderately so. Most pesticides have relatively low solubility in water.

What are the pros and cons of a pesticide being highly soluble in water? On the downside, being highly soluble in water means that a pesticide is more likely to be washed off a plant by rain or irrigation. Also, high water solubility means that a pesticide may be more easily washed into a stream or (especially in places with sandy soils) seep into groundwater. On the plus side, water-soluble pesticides may be absorbed more easily into a plant, since plants are largely made of water and the sap is mostly water.

Pesticides that can be applied to the soil beneath a plant and transported in the xylem sap tissue can reach pests that are otherwise hard to kill. Many sap-feeding insects, like scales, don’t move around much and may be protected by wax, or by the plant itself, from insecticides sprayed on the leaves and stems. These insects do take in lots of plant sap during feeding, however, so a pesticide in the sap can be easily ingested by the pest.

When systemic pesticides are applied to the soil, beneficial insects, birds and even pets and people are much less likely to encounter the pesticide in the form of residues or spray drift. The treatment of some trees (for example the big oak over the swimming pool) would be difficult to do safely without a systemic pesticide option.

Some of the common house and garden insecticides that are systemic include acephate (Orthene), imidacloprid (Bayer’s Tree & Shrub Insect Control, Merit) and dinotefuran (Greenlight Tree and Shrub Insect Control, Safari). You should be especially careful when using systemics if you have a shallow water table under sandy soils, or if you are applying the product near streams, lakes or water features. As with all pesticides, it is important to read and follow the label of a systemic pesticide carefully at the time of purchase, before use, and before discarding any leftover containers or product.

If you have questions, Jimmy Driggers, Garland County Extension Agent — Staff Chair, is available at or 501-623-6841. The Garland County Extension Office is located at 236 Woodbine, Hot Springs.

Master Gardener information

If you have an interest in gardening you’re welcome to attend the monthly Master Gardener meeting which is held on the 3rd Thursday of each month, 1 p.m. at the Elk’s Lodge. They’re open to the public and guests are always welcome. For information call the Extension office at 623-6841 or email Allen Bates at

EHC information

Would you be interested in joining an Extension Homemakers Club (EHC)? How about forming a new club in your community? EHC is the largest volunteer organization in the state. For more information, call Alison Crane, 501-623-6841 or email her at Follow Alison on Facebook @garlandEGF and @GarlandFCS, and EHC on Facebook @GarlandCountyEHC.

4-H information

If you’re between the ages of 5 and 19, you can join 4-H! We have a club for you, or you and a group of friends can organize your own club. For more information call Linda Bates at the Extension office, 623-6841 or email her at

The University of Arkansas Division of Agriculture is an equal opportunity/equal access/affirmative action institution. If you require a reasonable accommodation to participate or need materials in another format, please contact your County Extension office (or another appropriate office) as soon as possible. Dial 711 for Arkansas Relay.

Society on 11/19/2018

Fall Strategies for Spring Insect Control

How a systemic insecticide works

When you apply a systemic insecticide to the soil, roots take it up, and the plant’s internal transport system distributes it to every single leaf and twig. As a result, systemic insecticides actually protect plants from the inside out. Using systemics allows you to treat tall trees –at a fraction of the price of hiring a professional pest control company to spray foliage.

When insects feed on the treated plant (leaves or wood the pests eventually die. You may still see insects on a treated plant, and you may even see some damage. Using a systemic insecticide doesn’t keep insects from touching a plant, but it does kill them as they feed.Once a systemic insecticide is in the plant it protects against future attacks.

Once a systemic is applied to soil, different factors influence how quickly it will move throughout the plant. In ideal conditions, expect the insecticide to be distributed in 7-14 days and up to one month for larger trees.

How to get great results with systemics

A systemic insecticide may have a dry granule form that you sprinkle on soil and water in, or it may be a liquid that you mix with water and pour onto soil. With either type, you’ll get best results if you apply when shrubs and trees are:

  • Actively growing–When plants are actively growing, their roots take up water and nutrients from soil and will also take up the insecticide better. When treating plants in fall, time applications for early in the season, while leaves are still present on plants. In colder regions, apply systemic insecticides in very early fall. In warmer zones, wait until mid-fall or even later, depending on when or if trees become dormant for winter.
  • Healthy–When plants are healthy, roots are more actively taking up water and nutrients from soil and will also take up the insecticide better. If a tree or shrub is stressed and missing many of its leaves through pest or disease attacks or due to drought, it likely won’t take up the insecticide as effectively –and control results could be weakened.

Soil and weather conditions also have an effect on application. You’ll get best results with systemic treatments if:

  • Soil isn’t saturated–Plant roots won’t take up water if soil is already saturated when you make the application.
  • Soil isn’t overly dry–If drought has plagued plants prior to application, it’s a good idea to water the night before the application. This prepares roots to take up the insecticide.
  • Sunny, warm days follow–When days are warm and sunny, trees and shrubs lose water through their leaves, which means their roots take up more water (plus insecticide).
  • Soil isn’t frozen–Making applications too late in the season, after soil freezes, is a waste of time and money. Water (and insecticide) can’t move through frozen soil.

Other steps to protect plants

Other simple autumn strategies that help to eradicate pests from shrubs and trees include:

  • Cleaning up plant debris, such as fallen leaves or fruits. Destroy any materials that come from trees or shrubs that are already diseased or infested. Healthy materials can go into your compost pile.
  • Make sure trees and shrubs are well-watered going into winter. If fall rains are scarce, water landscape plantings during autumn. If a winter thaw occurs and the ground isn’t frozen, water plants again.

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