Controlling Vegetable Garden Insects without Pesticides

Here are some easy control measures that may avoid the need to use stronger methods.

A Red Aphid Highlighted on a Leaf Surface

Aphids

The aphid is tiny and pear-shaped with long antennae and two tubes projecting from its abdomen. Usually found on most fruits and vegetables, flowers, ornamentals, and shade trees throughout North America, they feed on plant sap. This distorts the foliage, causing leaves to drop. The honeydew excreted from the aphid left on leaves encourages sooty mold growth and feeding spreads viral diseases. To control these bugs:

• Wash plants with a strong spray of water
• Introduce native predators and parasites such as aphid midges, lacewings, and lady beetles
• If possible, cover plants with floating row covers
• Apply hot pepper or garlic repellent sprays
• For severe problems, apply horticultural oil, insecticidal soap, or neem oil

A Spiny Caterpillar Exploring a Leaf in Nature

Caterpillars

Caterpillars are the larvae of a butterfly or moth, having a segmented wormlike body with three pairs of true legs and several pairs of appendages. Caterpillars may be hairy, have warning coloration, or be colored to resemble their surroundings.cThey are found on many fruits and vegetables, ornamentals, and shade trees. Caterpillars chew on leaves or along margins; some tunnel into fruits. 

To deter them:

• Promote native predators and parasites
• Hand-pick them from your harvest
• Apply floating row covers

A Close-Up of a Cutworm Curling on a Leaf

Cutworms

Cutworms are gray or black segmented larvae that are fat and are about 1 inch long. Mostly active at night, they are found on most early vegetable and flower seedlings and transplants throughout North America. Cutworms chew through stems at ground level; they may completely devour small plants in May and June. For control:

• Use cutworm collars on transplants
• Delay planting
• Hand-pick cutworms curled below the soil surface

A Colorado Potato Beetle Feeding on a Leaf

Colorado Potato Beetle

The adult potato beetle is yellow-orange with ten black stripes on its wing covers. They are found on potatoes, tomatoes, cherry tomatoes, eggplants, and petunias throughout North America. Potato beetles defoliate plants, reducing yields or killing young plants. To control:

• Apply floating row covers
• Use deep straw mulches
• Hand pick
• Attract native parasites and predators
• Spray with neem oil

A Mexican Bean Beetle Resting on a Leaf

Mexican Bean Beetle

Adult Mexican bean beetles are oval, yellow-brown, and 1/4-inch long with sixteen black spots on their wing covers. Their larvae are fat, dark-yellow grubs with long, branched spines. These beetles are found on cowpeas, lima beans, snap beans, and soybeans in most states east of the Mississippi River as well as parts of Arizona, Colorado, Nebraska, Texas, and Utah.

Adults and larvae chew on leaves from below, creating a lacy appearance. To control:

• Apply floating row covers
• Plant bush beans early
• Hand pick
• Plant a soybean trap crop
• Spray with insecticidal soap or neem oil

A Flea Beetle on a Leaf with Feeding Damage

Flea Beetle

Flea beetles are small, dark beetles that jump like fleas when disturbed. Found usually on most vegetable crops, they are found throughout North America. Adults chew numerous small round holes into leaves (most damaging to young plants), and larvae feed on plant roots. For control:

• Apply floating row covers
• Spray plants with garlic spray or kaolin clay

Japanese Beetles Feeding on a Damaged Leaf

Japanese Beetles

Japanese beetle adults are metallic blue-green and ½-inch long with bronze wing covers. The larvae are fat white grubs with brown heads. They can be found on many vegetables, flowers, and small fruits in all states east of the Mississippi River. Adults skeletonize leaves, chew flowers, and may completely defoliate plants while larvae feed on lawn and garden plant roots. To control these insects:

• Shake beetles from plants in early morning
• Apply floating row covers
• Set out baited traps upwind of your vegetable garden on two sides and at least 30 feet away
• Spray beetles with insecticidal soap

As a premier tree care company in the San Francisco Bay Area, we at Arborist Now love sharing natural, eco-friendly ways to keep your trees and plants thriving. Check out our other blogs on gardening and pest control for more tips!