Carrots XXVIII – 3

Carrot Rust Fly

Whitney S. Cranshaw and Michael Brewer

Carrot Rust Fly

Identification (and life cycle/seasonal history)

The adult rust flies, Psila rosae (Fabricius), can be seen flying in May. They appear as a shiny green-bodied fly with a yellow head. The females lay the eggs at the base of the plant. The maggots hatch in three to seventeen days, when they squirm down through the soil to the plant. They appear as a legless maggot which is very slender and a yellowish-white in color. Maggots feed upon the smaller, tender tips of the roots. The entire root system can be in jeopardy as the larvae grow in both size and number. In about a month the larvae leave the root, or what is left of it, and pupate in the soil, near the root. Pupa are slender and brown and normally about ¹/₅ inches long. A second generation of adult flies emerges in August and a third generation may emerge in September. The carrot rust fly overwinters as either a pupa in the soil or a maggot in a root.

Plant Response and Damage

Carrots wilt with when the end of the tap root is eaten off. The root may become scarred and riddled with maggot passages. Feeding damage causes the plant tissue to become a rust-red color, thus the name of the fly. Both growing carrots and stored carrots are fair game for the larvae to feed upon, if temperatures permit.

Celery and other plants of the carrot family are attacked as well. Feeding damage results in the outer leaves yellowing and the entire plant wilting.

Management Approaches

Cultural Methods

Protection of seed beds can be accomplished with the use of a thin cloth (like hospital gauze) that has 20 to 30 threads per inch. Tack the cloth to the frames of the seed beds to exclude the flies from the plants.

Categories: Carrot, Carrot rust fly, Insects

Date: 05/05/02