The following list of pest descriptions and control measures provides a good starting point for tackling pest control in gardens throughout the United States and Canada. Control solutions are listed in order of environmental friendliness. Botanical sprays, which can have detrimental effects on beneficial insects and other animals, should be used only as a last resort.
1. Aphids (many species).
Tiny, pear-shaped; long antennae; two tubes projecting rearward from abdomen.
Host/Range: Most fruits and vegetables, flowers, ornamentals, shade trees. Found throughout North America.
Damage: Aphids suck plant sap, causing foliage to distort and leaves to drop; honeydew excreted on leaves supports sooty mold growth; feeding spreads viral diseases.
Control: Wash plants with strong spray of water; encourage native predators and parasites such as aphid midges, lacewings, and lady beetles; when feasible, cover plants with floating row cover; apply hot-pepper or garlic repellent sprays; for severe problems, apply horticultural oil, insecticidal soap, or neem.
2. Cabbage maggot (Delia radicum)
Adults: 1⁄4-inch gray flies. Larvae: white, tapering maggots.
Host/Range: Cabbage-family crops. Found throughout North America.
Damage: Maggots tunnel in roots, killing plants directly or by creating entryways for disease organisms.
Control: Apply floating row covers; set out transplants through slits in tar-paper squares; avoid first generation by delaying planting; apply parasitic nematodes around roots; burn roots from harvested plants; mound wood ashes or red pepper dust around stems.
3. Caterpillars (many species)
Soft, segmented larvae with distinct, harder head capsule; six legs in front, fleshy false legs on rear segments.
Host/Range: Many fruits and vegetables, ornamentals, shade trees. Range varies with species.
Damage: Caterpillars chew on leaves or along margins; droppings soil the produce; some tunnel into fruits.
Control: Encourage native predators, parasites; hand pick; apply floating row covers; spray with Bt (Bacillus thuringiensis) or spinosad.
4. Cutworms (several species)
Fat, 1-inch-long, gray or black segmented larvae; active at night.
Host/Range: Most early vegetable and flower seedlings, transplants. Found throughout North America.
Damage: Cutworms chew through stems at ground level; they may completely devour small plants; most damaging in May and June.
Control: Use cutworm collars on transplants; delay planting; hand pick cutworms curled below soil surface; scatter bran baits mixed with Btk (B.t. var. kurstaki) and molasses before planting.
5. Colorado potato beetle (Leptinotarsa decemlineata)
Adults: yellow-orange beetles with 10 black stripes on wing covers. Larvae: orange, hump-backed grubs with black spots along sides. Eggs: yellow ovals, laid in upright clusters.
Host/Range: Potatoes, tomatoes, eggplant, petunias. Found throughout North America.
Damage: Beetles defoliate plants, reducing yields or killing young plants.
Control: Apply floating row covers; use deep straw mulches; hand pick; attract native parasites and predators; spray with Beauveria bassiana or spinosad; spray with neem.
6. Mexican bean beetle (Epilachna varivestris)
Adults: oval, yellow-brown, 1⁄4-inch beetles with 16 black spots on wing covers. Larvae: fat, dark yellow grubs with long, branched spines.
Host/Range: Cowpeas, lima beans, snap beans, soybeans. Found in most states east of the Mississippi River; also parts of Arizona, Colorado, Nebraska, Texas, Utah.
Damage: Adults and larvae chew on leaves from beneath, leaving characteristic lacy appearance; plants defoliated and killed.
Control: Apply floating row covers; plant bush beans early; hand pick; plant soybean trap crop; put out lures to draw spined soldier bugs (predators) to your yard. Spray Beauveria bassiana, insecticidal soap, or neem.
7. Flea beetles (several species)
Small, dark beetles that jump like fleas when disturbed.
Host/Range: Most vegetable crops. Found throughout North America.
Damage: Adults chew numerous small, round holes in leaves; most damaging to young plants; larvae feed on plant roots.
Control: Apply floating row covers; repel the pests by spraying plants with garlic spray or kaolin clay; for a serious infestation, try repeated sprays of Beauveria bassiana or spinosad.
8. Tarnished plant bug (Lygus lineolaris)
Fast-moving, mottled, green or brown bugs, forewings with black-tipped yellow triangles. Nymphs: similar to adults, but wingless.
Host/Range: Many flowers, fruits, vegetables. Found throughout North America.
Control: Adults and nymphs suck plant juices, causing leaf and fruit distortion, wilting, stunting, and tip dieback.
Damage: Keep garden weed free in spring. Apply floating row covers; encourage native predatory insects; spray young nymphs with Beauveria bassiana or neem.
9. Japanese beetles (Popillia japonica)
Adults: metallic blue-green, 1⁄2-inch beetles with bronze wing covers. Larvae: fat, white grubs with brown heads.
Host/Range: Many vegetables and flowers, small fruit. Found in all states east of the Mississippi River.
Damage: Adults skeletonize leaves, chew flowers, may completely defoliate plants; larvae feed on lawn and garden plant roots.
Control: Shake beetles from plants in early morning; apply floating row covers; set out baited traps upwind of your garden on two sides and at least 30 feet away; apply milky disease spores or Herterorhabditis nematodes to soil; spray beetles with insecticidal soap.
10. Scales (more than 200 species)
Adults: females look like hard or soft bumps on stems, leaves, fruit; males are minute flying insects. Larvae: tiny, soft, crawling larvae with threadlike mouthparts.
Host/Range: Many fruits, indoor plants, ornamental shrubs, and trees. Found throughout North America.
Damage: All stages suck plant sap, weakening plants. Plants become yellow, drop leaves, and may die. Honeydew is excreted onto foliage and fruit.
Control: Prune out infested plant parts; encourage native predators; scrub scales gently from twigs with soft brush and soapy water, rinse well; apply dormant or summer oil sprays; spray with neem oil.