HOW TO CONTROL THE TOP 10 GARDEN INSECTS

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. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

Keep garden weed free in spring. Apply floating row covers; encourage native predatory insects; spray young nymphs with Beauveria bassiana or neem.

From Rodale's Ultimate Encyclopedia of Organic Gardening.