Biological Control of Northern Jointvetch in Rice by An Endemic Fungal Disease

Abstract

An endemic anthrocnose disease of northern jointvetch [ Aeschynomene virginica (L.) B.S.P.] incited by the fungus Colletotrichum gloeosporioides (Penz.) Sacc. f. sp. aeschynomene was discovered in 1969 at Stuttgart, Arkansas. When grown on solid or in liquid media, the organism grew rapidly and sporulated abundantly. From 1970 through 1972 water sprays of the fungus spores at 2 to 15 million spores per milliliter in 94 to 374 L/ha controlled northern jointvetch grown in the growth chamber, greenhouse, and field. The fungus controlled plants ranging from 5 to 66 cm tall. The disease developed on northern jointvetch most rapidly at temperatures of 23 to 32 C and at relative humidities above 80%. An incubation period of 4 to 7 days and up to 5 weeks was usually required to kill the weeds. The fungus was specific for Aeschynomene species since it was very virulent on A. virginica and only slightly virulent on Indian jointvetch ( A. indica L.). It did not affect rice ( Oryza sativa L.), soybeans [ Glycine max (L.) Merr.], cotton ( Gossypium hirsutum L.), or 12 other common field, forage, and vegetable crops or 15 common weeds.