The Lesser Bulb Fly, Eumerus strigatus Fallen, in Oregon

Abstract

The Lesser Bulb Fly, Eumerus strigatus Fallen, was first reported from Oregon in 1918. This pest is now established in the commercial onion and narcissus producing sections of the state. Brief descriptions of the various stages are given. The larvae have been found in onion, narcissus, and hyacinth bulbs; one grower has reported larvae in tulip bulbs. The seasonal history records are somewhat incomplete at the present date but may be briefly summarized as follows:- The insect passes the winter as fully grown larvae mostly in the bulbs but in some cases in the soil. During March and April the larvae leave the bulbs and migrate into the upper two inches of soil surface and pupate. The flies emerge and are active during April and May. Mating and egg laying take place at this time. The second generation of flies emerge during June, July, and August. These flies lay the eggs that produce some of the over wintering larvae although some of these larvae may pupate and emerge as flies in September and thus produce a partial third generation. The larvae are evidently capable of injuring healthy bulbs, but on this question the writer has no conclusive data. The flies, however, show a marked preference for diseased or injured plants for the bulk of their egg deposition. Bulbs infested by this pest are usually entirely destroyed. This pest can be partially controlled by the hot water treatment as applied for the Stem Nematode, Tylenchus dipsaci Kuehn. Sanitation is of value in the control of this pest. Corrosive sublimate and white oil emulsions applied as ovicides in the spring show promise of being practical methods of control for this insect.