Theses and Dissertations at Montana State University (MSU)

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Impact of harvest operations on parasitism of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae)
(Montana State University - Bozeman, College of Agriculture, 2005) Meers, Scott Byron; Chairperson, Graduate Committee: Wendell L. Morrill.
Wheat stem sawfly, Cephus cinctus, has been a long term pest management challenge for wheat producers in Alberta, Saskatchewan, North Dakota and Montana. Many studies have laid the groundwork for biological control of this pest. Two species of parasitoids, Bracon cephi and B. lissogaster, have been shown to effectively attack C. cinctus in wheat Triticum aestivum L. Their effectiveness as part of an integrated pest management plan, however, has been highly variable. A survey was conducted to assess the distribution of the two Bracon parasitoids. A two pronged approach was used to better understand parasitoid spatial dynamics and parasitoid promotion. First, intensive field sampling was performed to determine the overwintering location of parasitoid cocoons in wheat fields. Second, wheat stems were cut at varying lengths to stimulate harvest management techniques that producers could employ. B. cephi occurred at most locations where sawflies were an agricultural concern, although the level is sometimes very low. B. lissogaster was only found in wheat in Montana. The vast majority of overwintering cocoons (>80%) were consistently found in the bottom third of standing wheat stems when measured prior to harvest.