How to Prevent Garden Pests and Diseases

Common Garden Pests

Here are some common garden pest problems and suggestions about how to deal with them. A reputable garden center sells pesticides, repellents, and fungicides, keeping up with current regulations and usage. Each entry below names the pest, describes the damage, and suggests one or more controls.

Keep harmful insects away from your plants if you want a good harvest.

AnthracnoseThis tree blight of dogwood, ash, willows, and others causes leaves to develop brown spots, giving them a scorched look.Remove badly diseased branches. Prune for good air circulation.
Tiny green, gray, reddish, or brown pear-shape insects suck juices out of plant leaves and stems. You can see them clustering around the tips.Spray them off with a forceful jet of water, use insecticidal soap or rotenone, or bring in ladybugs to eat the aphids.
Beetles, variousYou can sometimes find beetles burrowing into flowers or leaves. They chew away foliage, leaving it very ragged.
Pick them off by hand or spray with rotenone. Look for beetle egg cases on the undersides of leaves and destroy them.
Caterpillars, variousLacy holes and big bites appear in leaves. Sometimes you can catch criminal caterpillars in the act.Kill them by hand or spray with Bacillus thuringiensis or pyrethrin.
Chinch bugsRound or irregular yellow patches appear in the lawn in hot, dry weather. This can mean chinch bugs, which are barely visible insects that suck juices from grass blades.Use an insecticide labeled for this problem and repeat at three-week intervals.
CutwormsCertain grubs and caterpillars live underground and chew through entire young plants, nipping them off at the base.
Destroy any cutworms you find by searching underground near the damage. Make protective collars for plants out of cardboard tubes two inches tall, setting each one around a plant, halfway into the soil.
GrubsPatches of dead turf and garden plants that vanish without a trace are signs that you may be dealing with grubs, the larvae of beetles.Control adult beetles by hand picking. If the problem is severe, use a recommended insecticide in late spring or early summer.
Lace bugsLeaves of azaleas and other plants become speckled and lose vigor. Lacebugs, with telltale small black specks, are the culprits.Spray the undersides of leaves with the appropriate remedy, after you have taken an afflicted leaf to the Agricultural Extension agent or garden center expert for confirmation of the diagnosis.
Leaf hoppers
Leaves are peppered with small round holes and begin to curl. Small, triangular hopping insects are the cause.Spray off light infestations with a garden hose before you turn to stronger remedies.
Leaf minersThere are white, curling trails inside the layers of a leaf. You can sometimes see a dark spot where the leaf miner is doing its damage.Remove all damaged leaves. Throw them in the trash, not the compost pile.
MealybugsA type of white, fuzzy scale insect, mealybugs make sticky clumps on leaves, buds, and stems and seriously weaken plants.Wash them off with Ivory soap and water solution, paint them with alcohol, or use pyrethrin to get rid of them.
MolesIf you have tunnels under your grass, it could be moles. They are carnivores that eat grubs and earthworms they find underground.Control insects that they feed on, or trap and remove the moles. Voles sometimes use similar tunnels.
ScaleLike mealybugs, scale insects cluster on stems. Some forms are dark and have a shell about an eighth of an inch long. Juvenile forms can move but adults stay in one place, sucking plant juice and spreading disease.
Wipe branches with alcohol or soapy water, and spray them in early spring with dormant oil.
Slugs and snailsSlimy trails are one clue left by these mollusks, and irregular holes in leaves and stems are another.Handpick and destroy, or use newer types of slug bait that are earth-friendly. A classic remedy is to trap them in shallow tubs filled with beer, set with the tops at soil level near the damaged plants. Or place a cabbage leaf near the damage, then look under it a day or two layer and find the critters hiding there.
Spider mitesFoggy little webs are nearly invisible, but the damage caused by spider mites can be extensive, killing leaves and plants.Spray with water often, for they prefer dry, dusty conditions. If the problem is extensive, use a miticide at three-day intervals.
SpittlebugsIn a mass of tiny white bubbles on plant stems, spittlebugs are hiding.They are not much of a problem, so unless they are pervasive, just spray them off with the hose from time to time.
WhitefliesSmall white insects shaped like houseflies but less than a quarter-inch long make their home on the undersides of leaves, laying eggs and sucking plant juices.
Wash plants off, use yellow sticky traps, improve air circulation, or destroy afflicted plants before the pests spread.

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