Green Peach Aphid and Turnip Aphid

In addition to cabbage aphid, the green peach aphid and turnip aphid can also infest cole crops. In the low desert, they are more common than cabbage aphid. However, in coastal areas, turnip aphid is rare and green peach aphid is less common than cabbage aphid.

The green peach aphid adults and nymphs are pale green to yellowish, and some individuals may be pinkish. The frontal tubercles at the base of the antennae are prominent and convergent on adults, which can be winged or wingless. Winged green peach aphids also have a distinct dark patch near the tip of the abdomen, which the wingless adults lack. On adults, the pair of rearward cornicles on the abdomen are markedly swollen or clublike at the tip.

The turnip aphid (also called mustard aphid) is a worldwide pest of cole crops. In California cole crop production, it is most commonly a problem in the low desert. These aphids are dark to olive green and have apparent cornicles, which are shorter than those of the green peach aphid. The waxy coating on the turnip aphid is also much thinner and less apparent than that of the cabbage aphid.

Green peach aphid can stunt seedling growth when abundant, and high numbers sometimes kill young seedlings or transplants. Economic damage is rare on older plants. Green peach aphids tend to feed on older leaves, and rarely enter heads of broccoli, Brussels sprouts, cabbage, or cauliflower.

Turnip aphids feeding on cole crop roots can seriously stunt, and even kill, plants.

In coastal cole crop-growing areas, both green peach and turnip aphids rarely require insecticide application. Because green peach aphids remain mostly on the older, nonmarketed leaves of cole crops, low to moderate numbers can be tolerated on older plants. Apply an insecticide to infested young plants if they show stress from feeding by green peach aphid.

In the low desert, infestations of both turnip aphid and green peach aphid often require insecticide application. Apply insecticide if green peach aphids or turnip aphids are numerous enough to contaminate the marketable heads. Time insecticide application to reduce aphid infestations before they reach the marketable heads. Turnip aphids typically require insecticide application between January and April.

Many general predators and parasitic wasps attack foliage-feeding aphids. Brown or black mummified bodies of aphids indicate the larvae of the parasitic wasps Aphidius matricariae, Aphelinus semiflavus, Diaeretiella rapae, Lysiphlebus testaceipes, or other parasites fed on the inside of the aphids and killed them. Sometimes natural enemies provide adequate biological control, especially in fields where residual, broad-spectrum insecticides are not applied. Consider installing insectary plants to attract natural enemies of aphids.

Remove infested culls and weeds around fields that may harbor aphids that move to crops. Turnip aphid problems tend to recur in the same fields; long-term rotation to other crops (such as lettuce) is advised.

Use primarily biological and cultural controls in an organically certified crop. Sprays of insecticidal soap and other organic insecticides are also registered for aphid control in organic cole crops.

Keep notes on the number of other aphids you see as you monitor for cabbage aphid. Apply insecticide to seedlings if they appear to be stressed by aphids based on monitoring information and observed damage. Older plants can tolerate low to moderate numbers of aphids. An application for cabbage aphid just before heading also controls the other foliar aphids.