Effect of planting date and climatic factors on soybean sudden death syndrome response in cultivars of different maturities

Abstract

A serious disease affecting soybeans (Glycine max (L.) Merr.) is sudden death syndrome (SDS). SDS is a relatively new disease,which has occurred in several states, causing great concern among farmers growing soybeans. This disease is caused by a soil-borne organism, Fusarium solani f sp. phaseoli strain A, which infects soybean roots. SDS affects mainly fields of high yield potential causing losses up to 80%. Leaf symptoms of SDS usually first appear after flowering as yellow spots between leaf veins, turning into necrosis. As disease progress leaves abscise and pods begin to drop causing yield losses. No effective control has been found for SDS, and varietal choice has been the only relief against it. Several reports have indicated that SDS is influenced by physical environmental factors. High soil moisture and cool temperatures during the reproductive period appear to encourage greater expression of disease while hot and dry conditions during this period seem to restrict disease development. It has previously been shown that varietal reaction to SDS is influenced by planting date though not in a consistent manner. The main purpose of this study was to evaluate the effect of planting dates on the expression of SDS in four varieties of different maturity groups. The study was conducted at Ridgway and Villa Ridge, two locations in Southern Illinois chosen based on their previous history of SDS infestation. Four cultivars from maturity group III to VI were used as main plot, and four planting dates spanning from mid May to late June were used as a subplot in a split plot design. Disease scores as well as growth stage were recorded weekly after disease