INFLUENCE OF SPORE DOSE AND WATER VOLUME ON A MYCOHERBICIDES EFFICACYIN-FIELD TRIALS

Colletotrichum orbiculare is a potential mycoherbicide agent for contr ol of Xanthium spinosum (Bathurst burr: spiny cocklebur). Applications of conidia at a range of doses in 3 water (carrier) volumes, plus and minus oil as an adjuvant, were assessed in field trials. Spore doses of 10(10) or 10(11) conidia/ha generally gave inadequate control but h igher doses of 2.5 X 10(11), 5 X 10(11), and 1 X 10(12) conidia/ha pro vided satisfactory control where environmental conditions were conduci ve to anthracnose development. High carrier volumes of 1000 liters/ha were generally not superior to volumes of 500 and 250 liters/ha. Oil a s an adjuvant did not enhance infection. Results were inconsistent but best weed control was obtained when the mycoherbicide was applied to young, actively growing plants during long dew periods in spring or ea rly summer. (C) 1995 Academic Press, Inc.