Biological Control of the Weed Sesbania exaltata Using a Microsclerotia Formulation of the Bioherbicide <i>Colletotrichum truncatum</i>

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 cm 2 of soil surface, caused 22% to 96% hemp sesbania plant mortality, after 14 days. Post-emergence treatment (fungus-rice aqueous formulation; 2.4 × 10 5 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 × 10 5 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%)

Production of Escovopsis weberi (Ascomycota: Hypocreales) Mycelial Pellets and Their Effects on Leaf-Cutting Ant Fungal Gardens

“…Here, it is reported for the first time that E. weberi , when cultured in a liquid medium, can produce hyphal aggregations regarded to be mycelial pellets (MPs). Under laboratory conditions, it is possible to induce certain species of fungi to produce these types of propagules [ 53 , 54 , 55 ]. The medium used here was originally developed to stimulate the production of blastospores by Metarhizium anisopliae [ 52 ].…”

“…Escovopsis weberi is a specialist parasite of Leucoagaricus gongylophorus and is a threat to leaf-cutting ant colonies [ 59 ]. The use of entomopathogenic, phytopathogenic, and nematophagous fungal MPs for biological control was studied and shown as a potential alternative to chemical control [ 45 , 46 , 47 , 55 , 58 , 73 , 74 ]. The application of Escovopsis MPs could also have the potential for use in biological pest control programs due to its capacity to affect colony integrity and remain viable for long periods.…”

Bioherbicides: An Eco-Friendly Tool for Sustainable Weed Management

“…Under greenhouse conditions, the conidial suspensions of Colletotricum truncatum with the addition of an invert oil emulsion decreased the moisture, yielding a 100% control of Sesbania exaltata (Raf.) Cory, while under field conditions a 95% control was achieved [170]. Bailey et al [171] reported that the use of the bioherbicide P. macrostoma in combination with nitrogen fertilizers to manage broadleaf weed species significantly enhanced the effectiveness of the bioherbicide, by 10 to 20%, against T. officinale.…”

Production and Stabilization of Mycoherbicides

“…It demonstrated its high efficacy against dandelion (Taraxacum officinale) (78 and 97% by pre-or post-emergence application correspondingly) [55]. The microsclerotia of Colletotrichum truncatum can be produced by both submerged and solid-state fermentation and to be effectively used for Sesbania exaltata control [56][57][58]. The development of "multi-propagule" formulations of mycoherbicides is possible as well [58].…”