Author(s)

Clyde D. Boyette, Hamed K. Abbas, Bobbie Johnson, Robert E. Hoagland, Mark A. Weaver

United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Biological Control of Pests Research Unit, Stoneville, MS, USA.
United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Crop Production Systems Research Unit, Stoneville, MS, USA.

Colletotrichum truncatum, grown on rice grain (3 to 4 weeks, 22°C to 24°C) produced a fungus-infested rice mixture of microsclerotia and conidia (spores) in a ratio of ~9:1, respectively. Greenhouse tests of this formulation (0.4 to 50 mg finely-ground fungus-rice product) which applied pre-emergence to 5 cm² of soil surface, caused 22% to 96% hemp sesbania plant mortality, after 14 days. Post-emergence treatment (fungus-rice aqueous formulation; 2.4 × 10⁵ microsclerotia ml^-1, 30% unrefined corn oil and 0.2% Silwet L-77 surfactant) of weeds surviving the pre-emergence application, resulted in 93% mortality, after 14 days. Based on greenhouse results, field tests were undertaken: 1) pre-emergence treatment (fungus-rice formulation at 2.4 × 10⁵ microsclerotia cm^-2), 2) post-emergence (fungus-rice product in 30% unrefined corn oil, 0.2% Silwet) only treatment, applied 15 days after planting and 3) pre-emergence treatment followed by post-emergence treatment (fungus-rice product in 30% unrefined corn oil, 0.2% Silwet) applied 15 days after planting to surviving weeds. Control treatments were: 1) autoclaved rice product sans fungus, 2) unrefined corn oil (30% unrefined corn oil, 0.2% Silwet in water) and 3) untreated plants. Planting dates were: early season (April-May), early-mid season (June-July), late-mid season (July-August), and late season (September-October). Weed mortality was recorded at 15 days for the pre-plus post-treatment, and at 30 days after planting for the pre-emergence only and the post-treatment only. The early season, pre-emergence treatment caused 67% hemp sesbania mortality (3-yr average) within 15 days and the post-emergence treatment caused 91% mortality of the surviving weeds. In the late-mid-season, pre-emergence treatment caused minimal (<5%) mortality at 15 days, but mortality in the post-emergence treatment was >80%. Results suggest that seasonal environmental conditions are important in the efficacy of this C. truncatum-rice product formulation when applied pre- or post-emergence to this onerous weed.

Bioherbicide, Biological Weed Control, Colletotrichum truncatum, Mycoherbicide, Sesbania exaltata, Microsclerotia, Solid Growth Media Substrate

Boyette, C. , Abbas, H. , Johnson, B. , Hoagland, R. and Weaver, M. (2014) Biological Control of the Weed Sesbania exaltata Using a Microsclerotia Formulation of the Bioherbicide Colletotrichum truncatum. American Journal of Plant Sciences, 5, 2672-2685. doi: 10.4236/ajps.2014.518282.