Title: Biological Control of the Weed Hemp Sesbania (Sesbania exaltata) in rice (Oryza sativa) by the Fungus Myrothecium verrucaria Authors
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2014
Publication Date: January 27, 2014
Citation: Boyette, C.D., Hoagland, R.E., Stetina, K.C. 2014. Biological control of the weed hemp sesbania (Sesbania exaltata) in rice (Oryza sativa) by the fungus Myrothecium verrucaria. Agronomy Journal. 4: 74-89. Interpretive Summary: Hemp sesbania, one of the most serious weeds in mid-south U.S. rice producing areas, can reduce quality and yield =50%. This weed is also problematic in row crops such as soybeans, cotton, corn and sunflower, has shown tolerance to the widely used herbicide glyphosate, and is not controlled in imazethapyr-resistant rice using the Clearfield™ system. A bioherbicidal fungus, Myrothecium verrucarria (MV) has been shown to control several leguminous weeds such as sicklepod and kudzu. The objectives of this research were to examine the effects of several mycelia inoculum rates of MV on various growth stages of hemp sesbania, and to determine if rice yields can be improved in field test plots in which this weed was effectively controlled. We found that = 95% control of hemp sesbania (= 20 cm) was achieved using a 50g/L mycelial wt. (dry weight basis) MV rate, with a concomitant rice yield increase (> 65% compared to control). These high weed control levels and increased rice yields were equivalent to those in plots treated with the herbicide, acifluorfen. This research demonstrates that an effective biological control agent such as MV can provide weed control and increase crop yield equivalent to that achieved by recommended synthetic herbicide application.
Technical Abstract: In greenhouse and field experiments, a mycelial formulation of the fungus Myrothecium verrucaria (IMI 361690; henceforth designated MV) containing 0.20% Silwet L-77 surfactant exhibited high bioherbicidal efficacy against the problematic weed hemp sesbania. High infection and mortality (100%) of hemp sesbania seedlings occurred within 48 h after fungal application in the greenhouse. In replicated rice field tests conducted over a three year period, MV controlled = 20 cm tall hemp sesbania plants at a 95% level using high inoculum concentration rates (50 g L-1 of dry mycelium). MV also controlled larger plants (= 60 cm tall) using this high inoculum rate. Rice yields were significantly higher in plots where weeds were effectively controlled. These results suggest that a mycelial formulation of MV has potential as a bioherbicide for controlling hemp sesbania in rice.