TITLE:
Biological Control of the Weed Sesbania exaltata Using a Microsclerotia Formulation of the Bioherbicide Colletotrichum truncatum
AUTHORS:
Clyde D. Boyette, Hamed K. Abbas, Bobbie Johnson, Robert E. Hoagland, Mark A. Weaver
KEYWORDS:
Bioherbicide, Biological Weed Control, Colletotrichum truncatum, Mycoherbicide, Sesbania exaltata, Microsclerotia, Solid Growth Media Substrate
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.18,
August
18,
2014
ABSTRACT: 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 (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.