Some success for its control has been achieved using a bioherbicidal agent, MV. Spore and mycelial formulations of MV tested alone and in combination with glyphosate for control of kudzu under greenhouse and field conditions demonstrated important synergistic actions between herbicide and this bioherbicide on kudzu.Palmer amaranth, originally native to the North American southwest, is an invasive species that has spread rapidly to eastern North America and in some other countries. Now widely distributed in the southeastern United States , this major weed has evolved resistance to several herbicides, including triazine, acetolactate-synthase inhibitor, and dinitroaniline herbicides use . Originally it was controlled with glyphosate,but the first glyphosate-resistant Palmer amaranth population was reported in Georgia in 2006 . Its rapid evolved resistance to glyphosate has now resulted in a major epidemic in the southern US and nearly 40 cases of resistance in this weed are now reported.

Initial host range studies of MV indicated that some phytotoxicity to redroot pig weed , and more recently tests on Palmeramaranth demonstrated bioherbicidal activity on plants that were sensitive or resistant to glyphosate .Hemp sesbania is an aggressive, nodulating legume weed that infests several majorcrops: rice , soybean , cotton and sunflower . It occurs in ditches, on stream banks, fallow areas and waste places in the US coastal plain of Virginia to Florida to Texas and rated as one in the top 10 most troublesome weeds in Arkansas, Louisiana,and Mississippi . Some single or multiple applications of herbicide treatments can provide control of hemp sesbania, but it exhibits some tolerance to glyphosate . MV was shown to be efficacious on hemp sesbania in host range tests and later field studies demonstrated its effectiveness on control of this weed in rice .It has also been reported as a pest in cotton, corn, and soybeans, reduced cotton yield by ~3% per weed per each 9 m row , and was classified as one of the world’s worst weeds.

Full-season interference by sickle pod was shown to reduce peanut yield by70%. Various herbicides have been evaluated of control of this weed, and some were highly efficacious. Although generally not currently a major problematic weed, sickle pod was the original host from which MV was isolated and this weed has been a target of several bioherbicide studies using MV .In early studies with MV, formulations of fungal spores were used as the bioherbicidal agent. However, more recent research showed that my celial formulations of MV were equally efficacious, easier to handle and lacked significant levels of trichothecenes . Very recently, we observed a fungal sector growing on a Petri plate during maintenance culture of MV. Preliminary examination of this spontaneous sector showed it to be a white and non-sporulating mutant. The objectives of further studies on this sector were to isolate and culture it, and to characterize its efficacy compared with MV-parent. To achieve this,greenhouse and bioassay tests were performed on several weeds with demonstrated susceptibility to MV as outlined above, i.e. , hemp sesbania, sickle pod, kudzu and glyphosate-resistant Palmer amaranth. Sicklepod and hemp sesbania seeds were obtained from field-grown plants in a weed nursery at Stoneville, MS.

Seeds of Palmer amaranth were collected from a population in Washington Co., MS and confirmed via bioassays to be resistant to this herbicide . Kudzu seeds were obtained from Adams-Briscoe Seed Co.,Jackson, GA 30233, USA. Silwet L-77 was procured from OSi Specialties, Inc., Danbury, CT, USA. Potato dextrose agar, were purchased from Difco Laboratories, Inc. . All other chemicals used in these studies were of reagent grade or higher purity. When MV is grown on PDA under alternating 12 h light/12 h dark cycles, concentric rings are produced. MV-Sector BSH formed during routine maintenance culture of MV and the sector was isolated and grown on PDA under the alternating light/dark regime as above. No rings or dark pigmented areas corresponding to spore production were observed during growth for several days. Microscopic examination of the white biomass of the sector confirmed that only mycelial growth occurred and that no spores were formed. Over several months of subculture, the sector remained genetically stable, retained high virulence and exhibited no genetic reversion to the wild-type parent . Growth of MV and MV-Sector BSH were very similar when grown on PDA or in shake-culture on soy flour: cornmeal: sucrose as described in the Material and Methods. This is the first report of a non-spore-producing mutant derived from this bioherbicidal strain of MV. Spray application of MV and MV-Sector BSH mycelial preparations on intact hemp sesbania and sickle pod seedlings generally demonstrated equal visual bioherbicidal activity on both species, 72 h after treatment. Injury symptoms were growth reduction, chlorosis, necrosis and desiccation.