Impact of Fall Cover Crops On Processing Sweet Corn and Snap Bean Yield and Pest Pressure.

Although many Ontario vegetable growers have been using cover crops for numerous years, questions remain as to what is the best cover crop to grow before specific crops.  A split-split-plot factorial design field experiment was conducted in 2011 to compare the impact of cover crop type (main plot 18x9m) and fall planting date (split plot 9x9m) on processing sweet corn and snap bean (split-split plot 4.5x9m) in terms of insect and disease pest pressure and crop yield and quality.  The cover crops were planted in early August and early September in 2008-2010 after cucumbers, which included a no cover crop control treatment and cover crop treatments of oat (Avena sativa L.), cereal rye (Secale cereale L.), oilseed radish (OSR) (Raphanus sativus L. var. oleiferus Metzg Stokes), forage peas (Pisum sativum L.), and hairy vetch (Vicia villosa Roth.) drilled at 81, 134, 13, 224, and 28 kg ha^-1, respectively  The following spring in 2011, the site was fertilized according to industry standards, disked and cultivated prior to planting processing snap bean (cv. Festina) or sweet corn (cv. Obsession). Generally, early-planted cover crops had greater biomass and N uptake compared to late-planted cover crops but cover crop planting date or type did not impact snap bean or sweet corn total or marketable yield.  At harvest, there were no differences among treatments for the incidence of anthracnose, bacterial blight, or insect feeding damage on bean pods.  At sweet corn harvest, the incidence of Lepidopteran feeding damage on cobs from the pea cover crop was lower than the no cover crop but no difference in the number of larvae was detected.  Preliminary results suggest neither yield penalty nor increased pest pressure with the cover crops tested in snap bean or sweet corn.  This study will be repeated in 2012 with sweet corn and snap bean crops rotated.