OVERWINTER SURVIVAL OF COLLETOTRICHUM-ACUTATUM IN INFECTED STRAWBERRY FRUIT IN OHIO

Colletotrichum acutatum, a causal organism for anthracnose fruit rot of strawberry, was recovered from 100% of all infected strawberry fruit exposed for 18 wk in the laboratory to constant temperatures of -12 and -30 C or six cycles of fluctuating temperatures of -12 or -30 C for 2 wk followed by 5 C for 1 wk. In a 2-yr field study (1988-89, 1989-90), C. acutatum was recovered from nearly 100% of fruit located on the soil surface or 5-8 cm below the soil surface after exposure to winter conditions for 3 mo (November through January), but recovery of C. acutatum decreased with time after 3 mo. After 6 mo of exposure, from November through May over a 3-yr period, the percentage recovery of C. acutatum from nonmummified fruit located on and below the soil surface, respectively, was: 1988-89, 80 and 67%; 1989-90, 60 and 0%; and 1990-91, 7 and 7%. Percentage recovery of C. acutatum was: 1989-90, 53 and 7%, and 1990-91, 47 and 40% from mummified fruit located above and below ground, respectively. This is the first report of C acutatum overwintering in a northern strawberry production region.