Characterization of disease reduction by cover crops in a no-till pumpkin production system

Production of pumpkin on a no-till cover crop of hairy vetch or hairy vetch and rye, in contrast to conventional tillage and bare ground, reduced disease and resulted in acceptable pumpkin disease management with fewer fungicide applications. In order to determine the mechanism by which disease is influenced by cover crops, experiments were conducted on pumpkins grown on no-till rye, hairy vetch, rye plus hairy vetch, or spring oat residues, or on bare ground. The effects of chemical, physical, nutrient and water content changes, and microbial population shifts on disease development were studied. Differences in soil-surface residue, splash dispersal, fatty acid profile, and soil nutrient content were examined for their relationship to pumpkin fruit rots and edema, a physiological disorder. A ground cover index was devised to integrate the percentage of ground cover at the beginning and end of the pumpkin growing season.; The hairy vetch plus rye cover crop combination provided the greatest season-long ground cover, followed by the rye treatment. A strong negative correlation was found between percentage of ground cover and amount of rain-driven soil splash. There also was a significant negative correlation between pumpkin fruit rot incidence and ground cover index. In years where differences were observed, fruit produced on bare ground had significantly greater Plectosporium blight and edema. Both Plectosporium blight and edema were negatively correlated with ground cover index.; There were no differences in inhibition of Fusarium solani f sp. cucurbitae growth when an in vitro assay was performed using soil taken from the experimental field plots. The survival of Sclerotium rolfsii sclerotia buried during the pumpkin season did not differ among cover crop treatments. There also was no significant difference in soil community profiles among cover crop systems or bare ground when fatty acid methyl esters were extracted and analyzed.; These data suggest that the primary mechanism of disease reduction in the cover crop pumpkin production system is physical. While this study shows that the use of cover crops can reduce disease, including edema of pumpkin, greater understanding of these relationships is needed in order to refine management strategies within a sustainable cropping system.