Integrated management of the Wheat Stem Sawfly by exploiting semiochemicals to enhance trap crops
MetadataShow full item record
The wheat stem sawfly, Cephus cinctus Norton (WSS) causes significant damage in cereal crops in the northern Great Plains of North America. Recently, the use of winter wheat as a trap crop to protect spring wheat from this insect pest in a wheat-fallow cropping system was evaluated, yielding promising results. Subsequently, the overall objective of this dissertation research was to improve the efficacy of winter wheat trap crops to manage the WSS. Oviposition behavior studies in the presence of hosts infested by conspecifics showed that WSS did not avoid infested hosts. These results confirmed the potential of a trap to provide a sink for multiple eggs, resulting in increased WSS mortality due to cannibalism. I identified suitable winter wheat cultivars based on agronomic characteristics that influence WSS behavior in conjunction with the emission of behaviorally active plant volatiles, as well as the performance of the cultivars in the area where the pest occurs. Results from this study identified five cultivars, Norstar, Morgan, BigSky, Neeley, and Rampart, with good potential as trap crops. Norstar emitted greater amounts of attractive volatile compound ⁷-ocimene, and was the preferred host in greenhouse choice tests. Based on these results, a perimeter trap cropping trial comparing three winter cultivars as traps (Norstar, Neeley and Rampart) to protect spring wheat was conducted for two consecutive years. Two spring wheat cultivars differing in suitability for infestation by sawflies were chosen as the main crop.WSS abundance was significantly greater in the winter wheat traps than in the adjacent unattractive spring cultivar Conan both years of the experiment and greater than an attractive spring cultivar Reeder in 2005. No differences in infestation were observed between winter cultivars, although greater numbers of eggs were found in Norstar than in Rampart traps. Swathing the trap crop before grain fill killed most larvae developing in the trap crop. Finally, I investigated the effect of a synthetic attractive compound, (Z)-3-hexenylacetate, on oviposition and found that application of this compound in a lanolin paste resulted in increased oviposition by females in greenhouse choice tests. The results obtained suggest that a trap cropping management strategy involving attractive and unattractive cultivars, and semiochemically assisted trap cropping by application of synthetic host volatiles, show potential to manage the WSS.