Sequence and Rotation Effects on Pest Incidence and Grain Yield of Double‐cropped Soybean and Pearl Millet After Winter Wheat and Canola

The crop-sequence and rotational effect of incorporating alternative crops of canola ( Brassica napus ) as a winter crop and pearl millet ( Pennisetum glaucum ) as a summer crop into a double-crop system of winter wheat ( Triticum aestivum ) and soybean ( Glycine max ) on crop pest incidence, stand, and grain yield was studied at Plains, GA. Twelve double-cropping sequences that substituted winter canola and pearl millet at various intervals in a wheat/soybean double-crop system were studied for five seasons. Previous crop sequence had little effect on stand and grain yield of winter canola but the incidence of Sclerotinia stem rot was greater when canola was grown continuously. Winter infestations of the Hessian fly, Mayetiola destructor (Say), in wheat were reduced following canola than wheat but tended to be greater following pearl millet than soybean. Stand of both pearl millet and soybean were reduced following canola as compared to wheat. Infestations of false chinch bugs ( Nysius raphanus Howard) were greater on seedling stands of both summer crops following canola. Stand losses in pearl millet were associated with false chinch bug infestations but stand losses in soybean most likely were due to several factors. Both crops compensated for stand differences so that grain yield was not affected by previous winter crop. Infection rate of soybean by soybean stem canker was not affected by previous crop sequence. In general pearl millet had little effect on pest incidence and agronomic performance of other crops studied. Stand reductions of summer crops probably can be mitigated so that the beneficial effects of canola in reducing insect and diseases in winter wheat can be realized in a wheat/soybean double-crop system.