Trap strip and field border modification for management of the wheat stem sawfly (Hymenoptera: Cephidae)

The alternate-year summer fallow wheat production system predominates in the semi-arid prairie regions of Montana. These farms consist of the current crop and idle fields in which the previous year's crop was located. Larvae of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), overwinter in post-harvest wheat stubble. Adults appear and disperse to new crops during the following growing season. Adults begin oviposition as soon as suitable hosts are encountered; therefore, larval infestations usually are concentrated along field borders. We tested several types of trap strips as intercepts to reduce dispersion of adult sawflies into fields. The most successful system was a fall-planted winter wheat trap that protected spring-planted wheat. These trap strips utilized the "border effect" as well as the higher attractiveness of the earlier maturing winter wheat. In another trial, losses were reduced by planting a semi-resistant solid-stemmed wheat cultivar within the border of a comparatively higher yielding hollow-stemmed cultivar.