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Spring Pest Management

Praying mantids, while impressive and fascinating, are not really beneficial predators for insect pests, as they eat good and bad bugs indiscriminately, including one another.

As the weather warms, the dormant insect population emerges to feast. When it comes to protecting the landscape from harmful insect pests, the experts seem in consensus on several points. The first line of defense against insect pests is healthy lawns and plants. Fertile soil and adequate water are key, but how best to keep the soil fertile is debatable. Some warn that overfertilizing with nitrogen makes plants more susceptible to pests. Too much nitrogen in leaves can attract the sucking insects: scales, mealybugs and aphids. Organic fertilizers are said to release nitrogen more slowly, but create more bacteria.

Other tips from the experts:

  • Use insect-resistant or insect-tolerant plants.
  • Buy plants from reputable sources to avoid importing insect pests.
  • Clear away dropped fruit and infested plant residues to reduce overwintering accommodations for pests.
  • Frequently monitor for insect damage.
  • Plant nectar crops and put out an insect bath to encourage beneficial insects that prey on insect pests.
  • Use the safe and inexpensive control methods of handpicking and washing them off plants with a strong spray of water.
  • Releases beneficial insects (predators and parasites) when pest populations are on the rise.
  • Put out barriers (mulches, collars, row covers, and tree bands) to keep pests from reaching plants.
  • Use microbial insecticides, horticultural oil, and homemade repellent sprays and dusts to fight common pests.
  • Spray or dust with botanical poisons only as a last resort (when large populations of insect pests invade).

As spring approaches, walk through the landscape and check the newest growth of each group of plants. The signs of insect damage are chewed areas, holes spots, wilting and curling. If there is evident damage, look for the culprit(s) by checking the underside of leaves first, as that is where most insects and their eggs will be. Also check where leaves attach to the stem. This will reveal most problems.

Ladybugs (lady beetles to the Brits): The larvae eat up to 40 aphids an hour and will dine on thrips, mealybugs, beetle grubs, scale insects, spider mites, whiteflies and other pest with soft bodies. Three thousand ladybugs (two ounces, when purchased) will control the aphid population in an acre of land.

Early identification of insect pests is important. Place traps around the landscape two or three weeks before you expect the insects to emerge. Sticky traps attract pest with color; yellow traps are good for aphids; round red traps for codling moths; sticky panels hung from an outer branch of a holly bush a few feet off the ground will let you know if flea beetles are about. Pheromone traps, which release a particular insect's sex hormones, are available for many species.

(Note: Trap placement is important. Hang traps on the south side of trees and plant groups. If you are trying to attract them with color, don't place the trap above the plant. Experts say many pest don't look up for color. Don't leave sticky traps out for longer than three to four weeks, as you'll end up attracting helpful insects.)

Tree Barriers

Barriers around tree trunks can arrest the progress of insects and also trap them. A cloth band 8-12 inches wide is smeared with Tanglefoot or some other sticky substance. These are put up at the end of September to keep pest from climbing up to winter in the tree. Barriers are also put out in the spring as trees begin to leaf. The barriers are good for catching gypsy moth larvae that migrate daily from the treetop down.

Goldenrod in northern Florida has been shown to attract more than 75 aphid predators, such as honeybees, lacewings, minute pirate bugs, soldier beetles, and spiders.

There are alternatives to sticky barriers. Cloth barriers with string bisecting the middle make a flap that blocks insect progress. Some use cardbord strips tied to the trunk with string with the exposed ridges of the paper facing the tree. Larvae will shelter in the space between the cardboard and the bark.

There is silicone-coated tape that makes it too slippery for ants and beetles to cross. There are also tapes sticky with cayenne pepper and salt to stop snails. Copper is toxic to slugs and snails and is also used to wrap around trees.

Eradication Methods

Once you've identified the pests, you don't have to immediately reach for the sprays or dust. You may want to employ sticky traps (this time to catch large populations of whiteflies or aphids, for example) or even manual methods. Coverings on the ground that offer shade to bugs will attract slugs and earwigs. Disposing these bugs twice a day can effectively keep the population down, as can handpicking bugs off plants as they start to populate. Spraying water on plants will cause the bugs to appear. A stronger spray of water can control aphids, mealybugs and spider mites. Spraying over consecutive days can eliminate these populations.

Bug Preditors and Parasites

The good news is that you don't have to worry about the vast majority of insects doing damage. It is estimated that less than one percent of all insect species are pests.1

Identifying the bad guys is obviously critical. You'll need a good resource, such as the American Horticultural Society's Pests & Diseases: The Complete Guide to Preventing, Identifying and Treating Plant Problems by Andrew Halstead, et al.

Assassin bugs feed on larvae of aphids, caterpillars, Colorado potato beetles, Japanese beetles, leafhoppers and Mexican bean beetles.

You must also recognize the insects that will help you keep the population of harmful bugs under control. Biological insect predators and parasites are one alternative to chemical pest warfare. Some will already be in your landscape, but if they aren't or if not in enough quantity, you can order them like any other commodity and release them into your outdoor environment to keep specific insect pests at bay.

Flies: Flies are abhorrent to most people but some are beneficial. Tachinids are the largest and most important group of insect parasitic flies, with over 1,300 species in North America. All species are parasitic in the larval stage. Most tachinids attack caterpillars and adult and larval beetles; others prefer killing sawfly larvae, various types of true bugs, grasshoppers, or other types of insects. Many important pests in the North Central states are suppressed by tachinids. The female lays thousands of eggs directly on caterpillars. When tachinid eggs hatch, the maggots are ingested by the caterpillar and develop inside the host. In other species, the adult fly glues her eggs to the body of the host; the maggots then penetrate the host. Some adult female tachinids possess a piercing ovipositor that insert the eggs into the host.

Tachinids are the largest and most important group of insect parasitic flies, with over 1,300 species in North America. The female lays thousands of eggs directly on caterpillars and other insect pests.

There are also fly preditors, like the 2-3mm long aphid midge, which lays 150-200 eggs at night among aphid colonies. The larvae develop over 3-5 days, during which time they inject a toxin into the leg joints of aphids to paralyze them and then suck out the aphid body contents through a hole bitten in the chest. Each midge can eat 4-64 aphids a day. After the fifth day, they burrow into the soil to spin their cocoons and emerge as adults in two weeks.

Other useful flies in the landscape and their victims: damselflies (aphids, leafhoppers, treehoppers, caterpillars, immature insects); fireflies (larvae feed on slugs, mites and small crawling insects); robber flies (bees, beetles, flies, grass-hoppers, grubs, leafhoppers, wasps); and syrphid flies (aphids, leafhoppers, thrips).

Green lacewing larvae (Chrysopa carnea) may be the most beneficial insect you can buy. You can purchase them in egg or larval form. They attack aphids, mealybugs, mites, scale insects, whiteflies and the eggs of caterpillars, mites and thrips.

Beetles are useful predators. We all recognize lady bugs, or as they're called in the U.K., "lady beetles." There are many families of beetles, each boasting hundreds of species. Beetles have hard forewings that cover their underwings and all have chewing mouths. Some beetles, certain weevils, have fused wing covers and can't fly. Ground beetles eat snails and slug eggs, root maggots, root weevil grubs, cultworms and small potato beetle larvae. The fiery searcher runs right up trees to feast on armyworms or tent caterpillars, and rove beetles live part of their lives in the soil. The small, hemispheric beetles, like the hister, tiger and firefly, eat slug and snail eggs and insect larvae. Rove beetles (eat mites beetle larvae, aphids and small worms), soldier beetles (aphids, small beetles, caterpillars, grasshopper eggs, spider mites) and tiger beetles (aphids, caterpillars, other crawling insects) are also a benefit.

The female Anagyrus ananatis (a chalcide parasite wasp) with its host, a mealybug. Parasite wasps are are one of nature's great insect pest controllers.

As an aside, Charles Darwin's first "wildlife" interests as a youngster was collecting beetles. He was intrigued by the incredible variety. He relates that out for a field trip one day he spotted a species he'd never seen. Excited, he caught the beetle, but immediately saw another kind he wanted and picked that up, too. When he saw a third specimen while holding a beetle in each hand, and afraid of losing the opportunity to add all three to his collection, he put one of the beetles in his mouth and nabbed the third.

Other preditor/parasite helpful insects and their victims:

Assassin bugs: feed on larvae of aphids, caterpillars, Colorado potato beetles, Japanese beetles, leafhoppers and Mexican bean beetles.

Bigeyed bugs: found in western North American, they prey on aphids, chinch bugs, leafhoppers, spider mites and most immature insects.

Damsel bugs: aphids; leafhoppers; small caterpillars.

European earwigs: common aphid and Aphis pomi that attack apples, plums, pears, spirea, dogwood and flowering crabapples and quinces.

Spiders: Spiders are of course classified as arachnids, not insects. They are among the first predators to emerge in the spring. Don't be arachnidphobic, they're truly wonderful insect predators. The more the merrier (I'd like to see someone convince my daughter of that pearl). Spiders like to build webs in camphorweed, goldenrod or asters.

Beneficial Bugs to Buy

Green lacewing larvae: These larvae (Chrysopa carnea) may be the most beneficial insect you can buy. You can buy them in egg or larval form. They attack aphids, mealybugs, mites, scale insects, whiteflies and the eggs of caterpillars, mites and thrips. Lacewings don't like the cold, so wait for 70? temperatures. To keep lacewings in your landscape, plant wild carrot, yarrow or oleander; lacewings also enjoy wheast or an equal mixture of sugar and brewer's yeast in water.

Parasitic wasps: While yellow jackets and mud daubers feed caterpillars, flies and grubs to their offspring, the parasitic wasps are considered the most important biological group in controlling insect pests. They fall into four groups: chalcid, braconid, ichneumonid and trichogramma.

Braconids, sold as eggs, attack aphids, cucumber beetles, cutworms, gypsy moths and tent caterpillars.

There are 22,000 species of chalcids documented, but because they are so small, it's believed that a million species could exist! This group includes the world's smallest adult insect, the degenerate male of Dicopomorpha echmepterygis, all of 0.11mm long. They invade aphids, asparagus beetles, leafhoppers, scale insects, whiteflies and various caterpillars and beetles.

The ichneumonids are over an inch long with long ovipositors hanging down, generally mistaken for stingers. The adults lay eggs in eastern tent caterpillars, cutworms, fall webworms, sawflies, European corn borers and other larvae.

Damsel bugs enjoy feasting on aphids, leafhoppers and small caterpillars.

The tiny trichogramma kills eggs of insect pests (aphids, armyworms, loopers, fall webworms, leaf rollers, gypsy moths, mealybugs, scale insects, whiteflies and beetle larvae). Adults feed on nectar of the daisy and carrot families, so it's a good idea to plant them.

Aphid midges: A midge will lay about 250 eggs on an aphid; the larvae then eat the aphid.

Mites: Shakespeare observed, "Though she be but little, she is fierce." This describes the mighty mite of insect predators. Mites are part of the arachnid family (eight legs versus the six of insects). Said to be 1/50 of an inch (who's measuring?), they dine on plant-feeding spider mite, cyclamen, or rust mites with a piercing, sucking mouth. Some prefer thrips and fungus gnats; others (the Phytoseiidae family) like the leaf eaters, and yet others camp out in the top soil for fungi and fly larvae.

Ladybugs (lady beetles to you Brits): The larvae eat up to 40 aphids an hour and will dine on thrips, mealybugs, beetle grubs, scale insects, spider mites, whiteflies and other pest with soft bodies. You'll need 3,000 ladybugs (two ounces) to control aphids in one acre.

Natural Sprays

Bug Juice: spray made from crushed insect pests. Its effectiveness is questioned, but grinding up insects may release a warning scent.

Garlic spray: garlic, onion and chives effectively repel certain insects.

Hot pepper spray: can be an effective insect control.

Antifeed sprays: chemical produced by plants that deter insects (peppermint, Japanese flower glory and sagebrush are a few plants with this quality.) Green Ban is made in Australia from kelp, English ivy, sage, garlic and eucalyptus.

Caffeine and citrus peel also have insecticidal qualities.

Microbial Insecticides

Like us, our "friends" the insects get diseases from bacteria, fungi, nematodes, protozoa and viruses. Science makes these diseases available to you for insect pest control. This is an area carefully studied and tested before the microbial agents are registered. We'll only touch briefly on this area.


The most used bacterial control agent, which has been sold for decades, is Bacillus thuringiensis (BT). This bacteria forms spores that produce toxic materials inside. When the insect eats the spores, toxic crystals dissolve in its stomach and paralyzes the gut. The insect stops eating. As the spores germinate the insect's blood is poisoned; additionally, the spores also produce the toxin, thuringiensin. The insect usually doesn't stand a chance against this insidious bacteria.

Bigeyed bugs, found in western North American, prey on aphids, chinch bugs, leafhoppers, spider mites and most immature insects.

Its downside is a short toxic life; you can't count on it to spread. Science has isolated more than a 1,000 strains of BT. The most common varieties are BTK (strain HD-1), BTI and BTSD. Results vary depending on the BT variety and the bug. BTK achieves excellent results with alfalfa and tent caterpillars, bag, cabbage and span worms, and diamondback moths. It gets good results with many worm species and other varities of caterpillar.

BT is sold as wettable powders or as liquid concentrates for spraying.

The oldest commercial insect disease product on the market is milky disease spores, the answer to Japanese beetles since 1933. Bacillus popilliae and B. lentimorbus are usually combined in the soil, where it survives for years. The Japanese beetle grubs ingest the bacteria when feeding on grass roots. Infected grubs spread the disease. Some areas are reported to have diseased larvae appearing 45 years after the spores went into the sod.

New sod and grass should be treated with milky disease spores. The spores are sold as dust, and can be applied any time, except in frozen ground. Spreading spores only on grass will control the grubs, but the beetles can still migrate to plants nearby.

The disease is most effective in soil with temperatures exceeding 70?F. Apply 7-10 pounds of spore per acre, the equivalent of 10 ounces per 2,500 sq. ft.

Viral Diseases

Most of the insect disease viruses infect caterpillars and some flies. The most common, Gvs and NPVs, dissolve inside the insect's stomach and spread to other organs. Millions of viruses will replicate and literally burst open the insects body, spreading the virus to its surroundings. Predatory and parasitic insects are not harmed by these viruses. The U.S. and Canadian forest services use some viruses against gypsy moths and sawflies.

Fungal Diseases

Fungal diseases of insects are common in large populations of caterpillars, aphids and flies. Fungi produce mold that penetrate insect cuticles and infect the blood. Verticillium lecanii has been used for aphids, thrips and whiteflies.

Protozan Diseases

These one-celled animals live in the environment or as parasites that form spores. The Vairimorpha necatrix protozoan attacks various caterpillars; Nosema locustae targets grasshoppers and Morman crickets. They are sold as spores and mixed with wheat bran for palatability.

The tiny parasitic nematode is a worm that releases bacteria into the insect's body. An infected insect dies within one or two days from blood poisoning, making the little buggers the fastest-acing microbial biological control. Nematodes are best used to controal soil pests. You need to apply about 35,000 nematodes per sq. foot of soil or 15,000 per plant. They control various borers.

Chemical Controls

Insecticidal soap: Over 100 years ago, gardening books recommended sprays made with laundry soap. Soaps are the salts of fatty acids and kill insects on contact. Beetles are not as susceptible, though it does kill ladybug larvae. Home-mixed soap sprays are quite effective, but commercial ones are likely to be less toxic to plants. The soaps are generally used for soft-bodied insects (aphids, mealybugs, scales, thrips, whiteflies and mites). Commercial brands kill only 60-80 percent of aphids, 2 however, the remaining aphids can rebound in a week or two to their pre-spray population. The other problem, is that the soap kills the insects that kill aphids.

Mites, including these two-spotted variety, are part of the arachnid family. A mite will lay about 250 eggs onto an aphid; the larvae then eat the aphid.

Note: The minerals in hard water (calcium, magnesium, iron) combine chemically with the fatty acids in insecticidal soaps, rendering it less effective on insects and more damaging to leaves. To test if the water is too hard, add three tablespoons of insecticidal soap concentrate to a quart of water, mix, and wait 15 minutes. If a scum appears on the surface, find another water source for use with the insecticidal soap.

Horticultural oil sprays: These sprays are 1-3 percent petroleum oil with an emulsifier (such as soap) and mixed in water. This method has been used since 1787. It kills on contact to the insect or mite, but is not poisonous to people. The more viscous (thicker) oils are called dormant and are applied in the spring before growth starts, or in fall after the leaves fall. Summer oils are more refined and for use while leaves are still on the tree. Supreme oils are the highest quality and useful year around.

Diatomaceous Earth (DE): Diatoms are fossilized one-celled algae mined and milled into a powdery silica. It is used to filter dirt from pools, but it scratches and dries out insect bodies.

DE does not break down in the environment, and so remains an insecticide until it is washed away of distributed.

Botanical Poisons–the Final Resort

When manual methods, traps, parasites/predators, biological controls, chemical controls (natural sprays and dusts) don't do the job, the judicious use of botanical poisons (pyrethrum, tyania, rotenone, sabadilla, etc.) may be called for. Nature has many toxins, and though they are "natural," they are poisons. The up side is that botanical pesticides break down into harmless compounds within days and can be used to control infestations. Here a just three examples of botanical poison.

Pyrethrin: The powdered flowers of the pyrethrum daisy was used as far back as 1880 for mosquito control. Pyrethrins are concentrated in the seed of the flower and chemically extracted (not to be confused with pyrethroids, a class of synthetic pesticides). Pyrethrins are quick to kill flies, gnats, and mosquitoes. It's effective for many chewing and sucking insects (most aphids, cabbage loopers, celery leaftiers, codling moths, Colorado potato beetles, leafhoppers, Mexican bean beetles, spider mites, stink bugs, some thrips, pinworms, and whiteflies). It does kill ladybugs, is toxic to fish, but not to bees, birds or mammals. It is available in premixed sprays, liquid concentrates or wettable powders.

Rotenone: Derived from a South American legume, but occurring in 65 species of plants, it was first used to kill fish and used on crops beginning in 1848. It's a slow-acting nerve poison that does not damage plants but is very toxic to fish, birds and pigs. It works well for aphids, Colorado potato beetles, leafhoppers, plant bugs, spider mites, whiteflies and other chewing insects. It is not very soluble in water.

Ryania: This South American shrub is a contact and stomach poison that paralyzes. It is not toxic to plants, has a relatively low toxicity for mammals, and is highly water soluble. It controls many sucking insects. Ryania dust can be store at least three years.

European earwigs dine on common aphids and Aphis pomi that attacks apples, plums, pears, spirea, dogwood and flowering crabapples and quinces.

Phytotoxicity is the science dealing with insecticide or fungicide damage to plants. Make sure correct dilution is applied. Plants known to be harmed by a chemical will be listed by the manufacturer, but this information is not known for all plant and chemical interactions. If unsure, treat just a part of one plant and watch for adverse reaction. "Control domes" are used to test chemicals on an enclosed environment.


Breeding Plants for resistance

Some plants have physical or chemical characteristics that insects don't appreciate. Geranium leaves are not popular because of their sticky, fuzzy hairs; the sulfar compounds in garlic leaves bug bugs; the bitter tannins in oak trees take bugs elsewhere.

Companion Plants

Companion planting is the long held practice of planting certain plants near crops to reduce insect damage to crops. Companion planting does work, but not always because the plants repel insects, but because they attract predators and parasites. What attracts the predators and parasites is pollen and nectar. When it comes to selecting plants for a landscape, it makes sense to plant some companion plants on the borders of planting areas and sometimes within the area.

Here are a few companion plants that have been documented as helpful:

Goldenrod in northern Florida has been shown to attract more than 75 aphid predators, such as honeybees, lacewings, minute pirate bugs, soldier beetles, spiders and many parasites. Ivies attract the parasite of diamondback moths; marigolds bring hover flies; Queen-Anne's lace brings out many parasitic wasps and flies, Japanese beetle parasites, lady beetles and minute pirate bugs; sunflowers attract lacewings and parasitic wasps; sweet clover will bring honeybees and tachinid fly parasites of many caterpillars; white clover will help you control the landscape of aphids, cabbage worms, shelters ground beetles and spiders.


Know Your Pests

Sap-feeders: adelgids; aphids; leafhoppers; mealybugs; plant bugs; pysllids; scale insects; spider mites; spittlebugs; thrips; whiteflies.

Flower pests: aphids; birds, caterpillars; earwigs; Japanese beetles; pollen beetles; slugs; snails; strawberry bud weevil; thrips.

Root-feeders: black vine weevil grubs; cabbage maggots; carrot rust fly larvae; cutworms; nematodes; onion maggots; root aphids; root mealybugs; slugs; white grubs; wireworms.

Gall-formers: (pest that secrete chemicals into the plant causing abnormal growths called galls): adelgids; aphids; gall midges; gall mites; gall wasp larvae; nematodes; psyllids; sawflies.

Fruit pests: birds; codling moth larvae; European apple sawfly; Japanese beetle; nut weevil; Oriental fruit moth; pea moth larvae; plum curculio; raspberry fruitworm; squirrels; wasps.

Stem pests: the sap-feeding pests plus bark beetles, clearwing moth larvae; deer; rabbits; squirrels; voles.

Leaf pests: sap-feeders plus adult black vine weevils; beetles; caterpillars; earwigs; leaf-cutter bees; nematodes; sawfly larvae; slugs, snails.

Stink bugs are "true bugs," with the characteristic triangular-shaped dorsal area. They have sharp beaks for sap feeding and exude a foul odor from a pore on each side of the thorax. Stink bugs are good fliers and are beneficial for killing cankerworms (inchworms) that cluster beneath bark in early spring and can defoliate a tree and kill it.

True bugs" are a class (Hemipterans) of insects distinguished from the generic insects that most people call "bugs." True bugs have leathery forewings that cross over one another and lay flat against the body; the hindwings flold under the forewings. The middle back section of a true bug is triangular-shaped. They have sharp beaks for sucking their food. The Hemiptera group includes water scorpions, water boatman, backswimmers, water striders, plant bugs, bed bugs, assassin bugs, flat bugs, seed bugs, red bugs and stink bugs. All "true bugs" have three life stages: egg, nymph and adult. The nymphs generally start out as miniature versions of the adult with slightly different coloration. As the nymph grows through several molts, it appears more like the adult in size and coloration. The pest of the true bugs drinks the sap from plant tissues; the predatory ones drink blood. The helpful true bugs like the blood of aphids, beetle larvae, leafhopper nymps, small caterpillars, spider mites, and thrips.


1 & 2. Carr A; Smith M; Gilkeson L; Smillie J; Wolf B. Chemical-Free Yard & Garden. The Ultimate Authority on Successful Organic Gardening. Rodale Press, Emmaus, Pessnylvania.

Other Sources

Ball J, Ball L. Rodale's Landscape Problem Solver: A Plant-by-Plant Guide. Rodale Press.

Greenwood P; Halstead A; Chase AR; Gilrein D. American Horticultural Society: Pests & Diseases. Dorling Kindersley Publishing.

Gay K. Cleaning Nature Naturally. Walker and Company, New York.

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October 13, 2019, 6:46 pm PDT

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