Spinach Leaf Miner

species: pegomya hyoscyami
common names: spinach leaf miner
hosts: spinach, beets, chard and weeds including lamb's quarters, chickweeds and nightshade
notes:

Two species occur in Canada, P. hyoscyami (Panzer) and P. betae (Curtis), distinguishable from each other only by minute differences, mainly in the genital structures. Both were probably introduced from Europe before 1880, and now are generally distributed throughout North America.

Injury:

The larvae damage spinach, beets, chard and related plants by mining between the upper and lower leaf surfaces. They render leaf crops unfit as food and stunt root crops. Most damage is noticed late in the growing season.

Life History, Appearance and Habits:

The insect overwinters in the puparium in the soil. In April and May, the greyish, slender-bodied, black-haired flies appear in the fields. They are about 7 mm long. The females deposit small white eggs, singly or in one to five parallel rows on the undersurfaces of leaves. After hatching, the tiny maggots eat slender mines which expand into leaf blotches as the larvae increase in size. Mines of a number of larvae join to form larger blotches. When mature, larvae drop to the ground and pupate in the soil. There may be three or more generations each year.

Pest Management:

Early in spring, plow the susceptible field deeply to expose the overwintering pupae to environmental stresses. Destroy susceptible weeds, such as lamb's quarters and nightshade, as well as old crop remnants. In small plots, screen-covered frames can protect small plants of the host crop from egglaying flies. For information on control, consult your provincial Department of Agriculture.

THE FOLLOWING (UNTIL OTHERWISE NOTED) IS FROM: GERBER, H.S. 1983.
MAJOR INSECT AND ALLIED PESTS OF VEGETABLES IN BRITISH COLUMBIA.
MINISTRY OF AGRICULTURE AND FOOD.

Spinach Leaf Miner:

Pegomya hyoscyami (Panzer) Leaf miners form conspicuous silvery blotches on the foliage. This species also attacks weeds, including lamb's quarters, chickweed and nightshade.

Vegetables attacked:

Beet, chard, spinach

Injury:

Colorless blotches with a silvery overcast are formed by the larvae mining between the surfaces of the leaves. This makes bunched beets unmarketable. Heavy infestations stunt growth.

Insect:

The adult is a slender grey fly 4 mm long. They are frequently seen hovering over the host plants. Small green or white maggots feed inside the leaves, forming blotches.

Life History:

There are several generations a year; pupae overwinter in the soil. Flies lay eggs on the undersides of the leaves. Larvae enter the leaves, feed until mature, then drop to the ground, pupate, and emerge as flies.

Control:

Insecticides should be applied when mining damage is first observed. Two or three treatments at 10-day intervals may be needed. Early in the season infestations may be suppressed by destroying infested crop residues and weeds.