Factors influencing charcoal rot of melon in Arizona

Abstract

Studies were initiated to determine if drip irrigation contributes to increased incidence of Charcoal Rot, caused by Macrophomina phaseolina , in melons in Arizona. Soil samples from furrow- and drip- (with and without plastic mulch) irrigated fields were analyzed for soil chemical and physical parameters: pH, moisture, salinity and temperature; and for microbial factors: inoculum density, mycorrhizal infection, nematode abundance, and basal respiration. Results show a significant decrease in pH and increase in temperature in drip versus furrow-irrigated soils. Also, the interaction of pH, salinity, moisture, and irrigation type was significant for inoculum density of M. phaseolina which was up to 150 times higher in drip irrigated fields. In greenhouse trials, disease incidence increased significantly as salinity of irrigation water increased, but was not affected by root-knot nematode. Therefore, soil characteristics of drip-irrigated soils may contribute to a soil environment conducive to an increase in Charcoal Rot in melon.