Other Aphids

In addition to the bean aphid, foxglove aphid, and lettuce aphid—which are discussed separately—about ten other species of aphids are found on celery. Of these, green peach aphid and rusty banded aphid (also known as the hawthorn-parsley aphid) are the most common. These aphid species vary in color (from light green to black), size, and shape. All are soft-bodied insects. They form dense colonies on the undersides of celery leaflets and in some cases on the celery petioles. Winged aphids form under specific conditions of overcrowding or plant stress and disperse to other plants or fields.

Cotton or melon aphid is a small to medium-sized aphid. It is highly variable in color, ranging from lemon yellow to blackish green in different individuals, often within the same colony. Their color is commonly lighter during the hotter times of the year and darker during cooler periods, but both color forms may be found throughout the year. In some years this aphid may be quite common in celery.

Although cabbage aphid is not a common pest in celery, and is typically found on lettuce and cole crops, this pest can be a problem as their numbers increase inside the heart of celery plants. These aphids can be identified by a waxy covering that is gray to whitish. Their cornicle at the base of the abdomen is very short compared to that of other aphids.

Aphid density can be as high as several thousand per plant. These pests can inflict three types of damage to celery. First, they stunt plant growth and reduce yield through removal of significant amounts of sap. Second, they transmit viral diseases such as celery mosaic virus, celery calico, and cucumber mosaic virus, and occasionally celery yellow spot. Third, they contaminate celery produce, particularly fresh market celery, with honeydew and debris; this contamination can lower the crop value.

Several parasitoid wasps provide natural control of aphids in celery, most notably species in the genera Diaeretiella and Lysiphlebus. In some cases, these parasitoids can control high numbers of aphids over a few weeks. Predators such as lady beetles, syrphids, and lacewing also attack aphids. Preserve natural enemies by avoiding unnecessary insecticide applications and by providing acceptable habitat for these beneficials.

Destroy crop residue immediately after harvest. Avoid other aphid-favored crops such as lettuce in adjacent, upwind fields.

Use biological controls, cultural controls, and sprays of narrow range oil (mineral oil) and insecticidal soaps (potassium salts of fatty acids) in a certified organic crop.

Economic thresholds for aphids on celery have not been established. Aphid survival and development are historically greatest at temperatures below 80°F. On fresh market celery, infestations are more important when the petioles (stalks) start to form and when the rows begin to close. Infestations tend to be erratic in the field so sample several locations. Look at intermediate-age petioles to find the highest aphid numbers. Intensify field monitoring for aphids when adjacent fields with aphid-favored crops are harvested. Concentrate on field edges, particularly where celery fields border harvested lettuce fields.