Ma. Jackson et al., FORMULATION OF COLLETOTRICHUM-TRUNCATUM MICROSCLEROTIA FOR IMPROVED BIOCONTROL OF THE WEED HEMP SESBANIA (SESBANIA-EXALTATA), Biological control, 7(1), 1996, pp. 107-113
Submerged cultures of the biocontrol fungus Colletotrichum truncatum p
roduce high concentrations of microsclerotia (MS) when grown under spe
cific nutritional conditions. Previous studies have shown that MS surv
ived drying, remained viable following longterm storage at 4 degrees C
, and killed hemp sesbania seedlings when incorporated into potting so
il. In this study, dried preparations of C. truncatum MS were encapsul
ated in wetted formulations of pregelatinized corn hour pregelatinized
cornstarch, or a mixture of the two (1:1). Germination rates of micro
sclerotia immediately after formulation and drying were not significan
tly different, After storage at 4 degrees C for 18 months, MS germinat
ion rates were significantly lower for all formulations compared to no
nformulated MS, Dried MS were capable of producing mycelia or spores u
pon germination when plated on water agar. After 3 days of growth on N
oble agar, the MS-flour formulations produced significantly more conid
ia than those made with starch, starch-hour or nonformulated MS. By th
e 10th day of incubation, significantly more conidia were produced in
formulations containing starch-flour (similar to 10-fold) and flour (s
imilar to 50-fold) than in MS starch formulations and nonformulated MS
. Bioassays showed that all MS preparations incorporated into potting
soil incited disease in emerging hemp sesbania seedlings. A significan
tly higher incidence of disease was seen in seedlings grown in potting
soil containing flour-formulated MS. These results suggest that corn
flour formulations of C. truncatum microsclerotia can be used to incre
ase the effectiveness of this bioherbicide for controlling the weed he
mp sesbania and that increased conidial production may play a role in
improving biocontrol efficacy. (C) 1996 Academic Press, Inc.