Category : Insects
Aphids (Green peach aphid, Melon aphid)
Myzus persicae
Aphis gossypii
Symptoms
Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants
Cause
Insect
Comments
Management
If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver colored plastic can deter aphids from feeding on plants; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use
Armyworms (Beet armyworm, Western striped armyworm, etc.)
Spodoptera exigua
Spodoptera praefica
Beet armyworm larva
Symptoms
Singular, or closely grouped circular to irregularly shaped holes in foliage; heavy feeding by young larvae leads to skeletonized leaves; shallow, dry wounds on fruit; egg clusters of 50-150 eggs may be present on the leaves; egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance; young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside
Cause
Insect
Comments
Management
Organic methods of controlling armyworms include biological control by natural enemies which parasitize the larvae and the application of Bacillus thuringiensis; there are chemicals available for commercial control but many that are available for the home garden do not provide adequate control of the larvae
Cabbage looper
Trichoplusia ni
Cabbage looper
Symptoms
Large or small holes in leaves; damage often extensive; caterpillars are pale green with a white lines running down either side of their body; caterpillars are easily distinguished by the way they arch their body when moving; eggs are laid singly, usually on the lower leaf surface close to the leaf margin, and are white or pale green in color
Cause
Insect
Comments
Management
Looper populations are usually held in check by natural enemies; if they do become problematic larvae can be hand-picked from the plants; an organically acceptable control method is the application of Bacillus thuringiensis which effectively kills younger larvae; chemical sprays may damage populations of natural enemies and should and should be selected carefully
Cucumber beetles (Western striped cucumber beetle, Western spotted cucumber beetle, Banded cucumber beetle)
Acalymma vittata
Diabrotica undecimpunctata
Diabrotica balteata
Pumpkin plant infested with cucumber beetles
Western spotted cucumber beetle
Pumpkin plant infested with cucumber beetles
Western striped cucumber beetle
Banded cucumber beetle
Symptoms
Stunted seedling; damaged leaves, stems and/or petioles; reduced plant stand; plants may exhibit symptoms of bacterial wilt; scars on fruit caused by beetle feeding damage; adult beetles are brightly colored with either a green-yellow background and black spots or alternating black and yellow stripes
Cause
Insect
Comments
Management
Monitor new planting regularly for signs of beetle; floating row covers can be used to protect the plants from damage but will need to be removed at bloom to allow bees to pollinate plants; applications of kaolin clay can be effective for management of small beetle populations; application of appropriate insecticides may be necessary
Cutworms
Cutworms
Agrotis spp.
Peridroma saucia
Nephelodes minians
and others
Cutworms will curl up into a characteristic C shape when disturbed
Cutworm larva severing plant stem
Symptoms
Stems of young transplants or seedlings may be severed at soil line; if infection occurs later, irregular holes are eaten into the surface of fruits; larvae causing the damage are usually active at night and hide during the day in the soil at the base of the plants or in plant debris of toppled plant; larvae are 2.5–5.0 cm (1–2 in) in length; larvae may exhibit a variety of patterns and coloration but will usually curl up into a C-shape when disturbed
Cause
Insects
Comments
Management
Remove all plant residue from soil after harvest or at least two weeks before planting, this is especially important if the previous crop was another host such as alfalfa, beans or a leguminous cover crop; plastic or foil collars fitted around plant stems to cover the bottom 3 inches above the soil line and extending a couple of inches into the soil can prevent larvae severing plants; hand-pick larvae after dark; spread diatomaceous earth around the base of the plants (this creates a sharp barrier that will cut the insects if they try and crawl over it); apply appropriate insecticides to infested areas of garden or field if not growing organically
Flea beetles
Epitrix spp.
Systena spp
Symptoms
Small holes or pits in leaves that give the foliage a characteristic “shothole” appearance; young plants and seedlings are particularly susceptible; plant growth may be reduced; if damage is severe the plant may be killed; the pest responsible for the damage is a small (1.5–3.0 mm) dark colored beetle which jumps when disturbed; the beetles are often shiny in appearance
Cause
Insects
Comments
Management
In areas where flea beetles are a problem, floating row covers may have to be used prior to the emergence of the beetles to provide a physical barrier to protect young plants; plant seeds early to allow establishment before the beetles become a problem - mature plants are less susceptible to damage; trap crops may provide a measure of control - cruciferous plants are best; application of a thick layer of mulch may help prevent beetles reaching surface; application on diamotecoeus earth or oils such as neem oil are effective control methods for organic growers; application of insecticides containing carbaryl, spinosad, bifenthrin and permethrin can provide adequate control of beetles for up to a week but will need reapplied
Squash bug
Anasa tristis
Squash bug nymphs
Pumpkin leaves damaged by squash bugs
Close-up of squash bugs feeding on pumpkin fruit
Squash bug infestation on pumpkin
Pumpkin leaves damaged by squash bugs
Squash bugs feeding on pumpkin leaves and fruit
Symptoms
Speckled leaves which turn yellow and brown; wilting plants; dieback of runners; blemished fruit; fruit death; adult squash bugs are often misidentified as stink bugs; they are grey-black in color with orange and black stripes on the edges of their abdomen; nymphs are greenish gray in color and often covered in white powder; female squash bugs lay conspicuous copper colored eggs on the undersides of the leaves
Cause
Insect
Comments
Management
Destroy all crops residue as soon as possible after harvest or on plant death; apply row covers at planting to protect plants;organically acceptable control methods include applications of insecticidal soaps and oils
Squash vine borer
Melittia cucurbitae
Squash vine borer damaging vine
Symptoms
Wilting plants; holes in vines or at base of petioles; green frass (insect excrement) visible around holes
Cause
Insect
Comments
Management
Apply appropriate insecticide if eggs are found on leaves; plow plants into soil after harvest
Thrips (Western flower thrips)
Frankliniella occidentalis
Western flower thrips
Symptoms
If population is high leaves may be distorted; leaves are covered in coarse stippling and may appear silvery; leaves speckled with black feces; insect is small (1.5 mm) and slender and best viewed using a hand lens; adult thrips are pale yellow to light brown and the nymphs are smaller and lighter in color
Cause
Insect
Comments
Management
Avoid planting next to onions, garlic or cereals where very large numbers of thrips can build up; use reflective mulches early in growing season to deter thrips; apply appropriate insecticide if thrips become problematic