The effects of moisture and temperature on the survival of Colletotrichum acutatum on strawberry residue in soil

Abstract

Strawberry stolons inoculated with Colletotrichum acutatum, the causal agent of strawberry anthracnose, were buried in autoclaved or nonautoclaved Reiff fine sandy loam soil and kept at 5 or 10 °C in controlled environment chambers. Samples were examined monthly for 6 months to determine the survival of the pathogen from the number of recovered conidia and the percent conidial germination. Two soil moisture levels, with water contents of 26.8 or 35.3 g per 100 g of dry soil, were maintained at each temperature. Three isolates of C. acutatum (Wolfskill, Surecrop, and 102) from California strawberry performed similarly at the same temperature. The number of conidia recovered and percent conidial germination were the highest at 5 °C with a soil moisture level of 26.8%. Conidia recovered from buried stolons decreased progressively over the 6 months, from 5 × 104 to 0.5 × 104 per linear centimeter of lesion on stolons. The decline was more pronounced at 10 °C than 5 °C and at a higher soil moisture. Percent conidial germination remained between 80% and 90% for 4 to 5 months, fell to 40%–60% in the last period, and was particularly low at 10 °C and high soil moisture. Our results indicated that C. acutatum may survive the relatively short winter fallow season in strawberry nursery soil in California.