Wheat Insects

Russian Wheat Aphid, Diuraphis noxia.

Wheat>Close-up of Rusian Wheat Aphids

on leaf

The Russian wheat aphid arrived in the Great Plains in 1986, but recent years’ losses have been lower than in the decade following its invasion. Significant infestations in Kansas have generally been limited to the counties near the Colorado border.

This small, lime-green aphid has a football-shaped body and very short cornicles and antennae. These aphids prefer to feed on the newest growth of the wheat plant within rolled-up leaves that provide a protected microhabitat. Infested leaves exhibit purple, yellow or white longitudinal streaks along the leaves and leaf sheaths. Heavily infested plants may appear flattened, with young tillers lying almost prostrate to the ground.

High populations of Russian wheat aphids that persist for long periods can lead to serious crop losses. Risk of yield loss is highest when infestations develop in early spring. Fortunately in Kansas, climatic conditions and biological control by predators, especially lady beetles are normally quite effective in keeping them below damaging levels.

The recommended threshold for treatment varies with the expected yield. In spring, if wheat has a yield potential of at least 20 bushels per acre, treatment should be considered when 20 percent of tillers show symptoms and most have live aphids. In fields with a yield potential of 40 bushels or more, it may be economical to treat when as few as 10 percent of tillers are infested. When 30 to 40 percent of primary tillers are infested anytime between flowering and the soft dough stage, treatment may be advisable, but infestations confined to late-developing secondary tillers are less damaging to yield.

Populations that develop soon after the crop emerges in early fall can also be damaging but are unusual in Kansas. At this time, a 20 to 30 percent infestation of plants or tillers may warrant treatment.

Resistant Varieties

In areas with a history of Russian wheat aphid problems, resistant varieties are a potential management option. Varieties containing resistance to Russian wheat aphid include Ankor, Halt, Yumar, Prowers 99, Prairie Red and Stanton. However, in 2003 a new biotype of the pest was detected in Colorado that appears to have broken the resistance present in these varieties. This biotype is now reported to be widely distributed throughout eastern Colorado, and was found to be common in western Kansas in 2006. The new biotype is capable of very rapid population growth and can damage wheat very quickly, especially at warmer temperatures.

Seed Treatments

Seed treatments offer early season protection and may help reduce infestation in the western third of the state during periods of Russian wheat aphid activity.

Imidacloprid (Dyna Shield Imidacloprid, Gaucho, Gaucho Grande, Gaucho XT, Imida and Senator) Reference labels for information on how these products should be applied. Some products indicate that they are to be commercially applied and others allow end-use seed treatment on agricultural establishments in liquid or slurry treaters at or immediately before planting. Some carry the carry the warning to not graze or feed livestock in treated areas for 45 days after planting.

Thiamethoxam (Cruiser)

This chemical is commercially applied to seed at 0.75 to 1.33 fl. oz. of Cruiser 5FS per 100 pounds of seed. It is often combined with a fungicide treatment.

More information on the biology and life history of the greenbug can be found in KSRE publication MF 2666: Russian Wheat Aphid

Please refer to the most recent version of the Wheat Insect Management Guide for control options.

Page last updated 10/30/2013 by J.P. Michaud.