Adult sugarbeet root maggot flies approximate house flies in size and appearance (approximately 1/4 inch).
The wings of this fly are transparent, with a smoky-brown patch on the front one-third of the way from the wing base.
The legs have yellowish-white stripes on the terminal segment (“ankles”), while the rest of the leg is black.
Females have sharp abdomens, while males have broader abdomens. The eggs are white, long, and slightly curved.
The larvae are white, legless maggots that grow to be about a third to a half-inch long. The front end is blunt, while the back end tapers to a point.
Pupae are elongate, tan to brown capsules about 5/16 inches long.
Host plants:
Only larvae harm. They diminish tonnage and sugar content by scraping the root surface with their rasping mouth hooks. They do not burrow into the beet like wireworms, nor do they eat aboveground like cutworms or crown borer larvae. Only maggots that emerge from eggs during the current growing season are harmful. During the spring, overwintering larvae never eat the crop.
Damages caused by Sugarbeet Root Maggot:
Sugarbeet root maggots feed on the root’s surface, creating surface scarring. Heavy feeding may cause deeper scarring and deformed roots. Because the maggots feed on and cut the tap root, a heavy infestation of the sugarbeet root maggot can cause considerable stand loss, especially in tiny plants. Plants that have suffered serious damage become excessively wilted or die. If stands are not lowered, losses from diminished plant vigor may occur.
Life history and habits:
Sugarbeet root maggots overwinter as fully formed larvae in soil 10 to 14 inches deep. When the weather warms up in the spring, the larvae crawl up close to the soil surface and pupate. Fly emergence and activity peak occurs in late May or early June. Females deposit their eggs in the top 1/4 to 1/2 inch of soil at the base of sugarbeet plants. Eggs are deposited in batches ranging from a few to as many as 40; a female will lay more than 100 eggs during her lifetime. In dry soils, the survival of eggs and early larval stages is severely decreased. The larvae start feeding on the sugarbeet roots and feed for three to four weeks. Feeding ends between late June and early July, but the larvae stay in the soil near the sugarbeet roots.
