Crucifer Pests
 

Aphids
Several species including Myzus persicae, Hyadaphis erysimi and Brevicoryne brassicae

Found worldwide

Damage Symptoms

Leaves are curled, wrinkled, or cup-shaped. Plants in all growth stages can be damaged. With severe infestations the leaves wilt and the entire plant dies.


Insect Characteristics

Piercing-sucking mouthparts. They are small, soft-bodied, and pear-shaped. They vary from yellow to green to black. Some have transparent wings and prominent eyes. Note the small tubes arising from either side of the back of their bodies (tail region).


Where to Look

Select leaves that are beginning to curl, show signs of wilting, or are partially dried up. Look within the cupped leaf for colonies of the pear-shaped insects. They vary in size from 2 to 4 mm in length.


Technical Information

Aphids have continual generations and many hosts. When populations on one plant are high, winged forms are produced that fly to adjacent plants to establish new colonies. Aphid colonies are commonly visited by ants that feed on the honeydew secreted by the aphids. This honeydew also serves as food on which a sooty mold grows. Some aphid species are virus vectors. Many different vegetables serve as hosts of aphids.


Control

Biological: Natural enemies, such as parasitic wasps and predators, are usually numerous enough to keep aphid populations from building to damaging levels. Adults and larvae of coccinelid beetles and syrphid fly larvae are well-known predators. Wet weather will cause fungal pathogens to kill aphids.

Cultural: Remove weeds. Destroy and remove crop residues immediately after harvest. Aphids are less attracted to mulched plantings since host plants are less highlighted compared to a bare-soil background.

Chemical: Soap sprays may be used, but thorough applications (especially on the underside of leaves) are needed as soap only kills those pests that it comes into direct contact with. Aphids, especially cabbage aphid, naturally hide in protective areas of the plant. Spray no more than three times with the same product or rinse plants to prevent damage to leaves.

Among synthetic insecticides, dimethoate and pirimicarb are effective, but check local recommendations. The use of these and other broad-spectrum insecticides early in the cropping season will reduce the natural enemies of aphids, leading to a rapid increase in aphid populations.