CSU Will Survey Fields This Spring for Wheatstem Sawfly

The wheat stem sawfly, Cephus cinctus Norton, has been one of the most important pests of wheat in the northern Great Plains for more than 100 years. The sawfly originally attacked spring wheat, however, by the mid-1980’s, damage to winter wheat was reported in Montana.  Since then, the sawfly has become more common in winter wheat, and reports of damage indicate spread into southeastern Wyoming and the Nebraska Panhandle. In 2011, this pest was found damaging winter wheat along Highway14 northeastern Colorado.

Sawfly larvae feed throughout the wheat stem, reducing grain yield by up to 20%. However, the most dramatic damage is due to lodging which occurs after the stem has been girdled by the larvae, and losses of up to 80% due to lodging have been reported. Annual economic losses in Montana average $25 million.

Effective chemical controls are not available. Several cultural controls help to reduce, but not eliminate, infestations.  Solid-stemmed cultivars are resistant, but may not yield as well as well adapted hollow-stemmed varieties in the absence of sawfly infestation.   Resistant cultivars generally are recommended only for areas at high risk for sawfly problems.  See the High Plains IPM Guide (http://wiki.bugwood.org/HPIPM:Main_Page) and the CSU wheat stem sawfly fact sheet (http://www.ext.colostate.edu/pubs/insect/05612.html) for more details on biology and management.

In April, 2012, Colorado State University personnel will start a three-year wheat stem sawfly survey to (1) determine the extent and rate of spread of wheat stem sawfly into Colorado wheat production areas; and (2) identify wheat production areas most likely to benefit from the use of solid-stem winter wheat cultivars. Two hundred fields will be sampled in eastern Colorado wheat producing counties.  Fields will be mapped and categorized as to infestation and sawfly risk.  If you suspect wheat stem sawfly activity or damage in your area, please contact Frank Peairs (frank.peairs@colostate.edu).

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