Managing the wheat curl mite is critical in managing the disease risk to winter wheat, particularly in central and western Nebraska. This article outlines key risk factors to manage.
Four videos illustrate the spread of wheat curl mites among neighboring wheat fields and the importance of controlling these mites to curtail the development of three key viruses of winter wheat in Nebraska.
For wheat growers, one aspect of being a good neighbor is controlling volunteer wheat after harvest to stop wheat curl mites from moving into the new crop of wheat and transmitting viruses, particularly wheat streak mosaic virus. Volunteer wheat should be controlled in time to provide a two-week break in the green bridge.
Wheat streak mosaic virus (WSMV) problems have been extensive throughout the western Great Plains this year, significantly reducing the yield potential of many fields. A critical key in managing this threat in the next crop is elimination of volunteer wheat. Tillage or chemical weed control should occur at least one month before planting to allow host plants time to dry up and cease being a host.
Timely control of volunteer wheat and other weeds is key to managing yield loss risk in your 2018 crop. Yield-limiting risk factors affected by weed control include wheat streak mosaic and other diseases, insects (wheat stem sawfly and disease vectors), moisture loss, and increased weed seed production.
Figure 1. Severe symptoms of wheat streak mosaic in volunteer wheat in sunflower stubble in Deuel County in November 2016. Such a field significantly increases the risk of infection of wheat in nearby fields. (Photo by Gary Hein)
While the mild fall promoted wheat establishment, it also favored survival of wheat curl mites, the leading vector of several viruses common to Nebraska wheat. While much of the state's wheat crop entered winter in very good condition, growers are urged to scout for viruses this spring and assess yield potential of individual fields when making management decisions.
By far, the greatest risk of losses from mite-vectored viruses occurs when there is a summer "green bridge" of volunteer wheat emerging before harvest. This almost always occurs as a result of wheat seed head shatter from hail storms (Figure 1).
