How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PESTS

Several other aphids may occur on cole crops. The most common is the green peach aphid, which is a yellow-green aphid with prominent tubercles at the base of the antennae. None of the other aphids occurring in cole crops have the waxy coating that characterizes the cabbage aphid. Green peach aphid and turnip aphid also tend to be more randomly dispersed around the plants than the dense colonies of the cabbage aphid. The turnip aphid, a species that is a worldwide foliar aphid pest, occasionally infests the roots of cole crops in coastal California. These aphids are dark to olive green and unlike other root aphids, have visible cornicles.

DAMAGE

When populations are heavy, green peach aphid can stunt seedlings; however, economic damage rarely occurs on older plants because green peach aphids tend to feed on older leaves and rarely enter heads of broccoli, cauliflower, cabbage, or Brussels sprouts. Turnip aphids on the roots of cole crops can seriously stunt and even kill plants.

MANAGEMENT

These aphids rarely require treatment in cole crops. Because they remain mostly on the older, nonmarketable leaves of cole crops, low-to-moderate populations can be tolerated on older plants. High numbers of green peach aphid can kill young seedlings or transplants, so treat infested young plants if they show stress from feeding by this aphid. The same general predators and parasites that attach cabbage aphids also attack these aphids.

Biological Control
Many predators and parasites attack aphids, especially in fields that are not sprayed or sprayed with less toxic materials. These natural enemies, including general aphid predators and the parasites Lysiphlebus testaceipes, Aphidius matricariae, Aphelinus semiflavus, and Diaeretiella rapae, may provide adequate control under certain circumstances.

Cultural Control
Remove infested culls and weedy species around fields that may harbor the aphid between crops. Turnip aphid problems tend to recur in the same fields. Long term rotation to other crops may be advised.

Organically Acceptable Methods
Biological and cultural controls as well as sprays of insecticidal soap, which can give partial control of aphids, are organically acceptable methods. Insecticidal soap sprays, however, may be phytotoxic under some conditions and rates, especially in Brussels sprouts and cabbage.

Monitoring and Treatment Decisions
No special monitoring is needed for green peach or turnip aphids in cole crops; keep notes on them as you monitor the cabbage aphid. Treat seedling plants if they appear to be stressed by aphid populations. Older plants can tolerate low to moderate populations. If applications are made for cabbage aphid just before heading, other foliar aphid species will be controlled as well.

PUBLICATION

UC IPM Pest Management Guidelines: Cole Crops
UC ANR Publication 3442
Insects and Mites
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgments for contributions to Insects and Mites:
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
W. E. Chaney, UC Cooperative Extension, Monterey County
N. C. Toscano, Entomology, UC Riverside

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