Evaluation of Composted Manure as a Growth and Delivery Substrate for the Biological Weed Control Agent Gliocladium virens in Sustainable Vegetable Production Systems

1996 Annual Report for LNC96-100

Project Type: Research and Education
Funds awarded in 1996: $70,000.00
Projected End Date: 12/31/1998
Matching Non-Federal Funds: $35,851.00
Region: North Central
State: Indiana
Project Coordinator:
Stephen Weller
Dept of Horticulture and Landscape Architecture, Purdue University

Evaluation of Composted Manure as a Growth and Delivery Substrate for the Biological Weed Control Agent Gliocladium virens in Sustainable Vegetable Production Systems

Summary

The overall objective of this research was to develop a more efficient and potentially useful system for growing the fungus G. virens in order to deliver the biological herbicide to the crop field in a form that was active against weed growth in vegetable crops.

Specific objectives were:

1) To use composted chicken manure (CCM) as a substrate for growth and delivery of G. virens as a biological weed control agent for use in sustainable vegetable production systems;

2) To use annual rye as a cover crop (Secale cereale) in association with G. virens as an alternative to conventional herbicides in vegetable production systems; and

3) To assess the effectiveness of these environmentally friendly production systems and disseminate information to the farming community.

During the first year of this project studies were initiated in the laboratory, greenhouse and field to address the specific objectives. Initial studies were conducted in the laboratory to develop a method by which the inputs and time required to inoculate and deliver the fungus in an active form to the field could be reduced. Results in year one showed that the required nutrients and carbon source necessary for fungal growth on the CCM could be reduced by one-half, that the required incubation time prior to field delivery could e reduced from 28 to 7 days and that there was no need for sterilizing the CCM prior to inoculation with G. virens.

These results provide a reduced cost system for mycoherbicide preparation and allowed greater flexibility in preparation of the substrate for field delivery. During the second year, the combined effect of the reduced inputs in substrate preparation was tested in the laboratory and in the greenhouse.

Results in year two indicated that reduction of the nutrient and carbon source to one-half caused a decrease in viridiol (the active herbicide component) production over time. In the greenhouse, the non-sterilized treatment incubated for 7 days provided the best mycoherbicidal activity.

In addition to the substrate preparation studies, field experiments were conducted over a two year period in tomato, pumpkin and snap bean crops to assess the potential of the mycoherbicide as a weed control agent. The studies showed that the mycoherbicide had activity under field conditions, although the overall effectiveness of the mycoherbicide varied considerably among the tests. G. virens control of weeds was inconsistent when compared to conventional herbicides. G. virens inoculated chicken manure did, under certain conditions, provide acceptable control of broadleaf weeds; however, its activity against grassy weeds was poorer. The activity of G. virens was better when applied to early season crops prior to extremely hot and dry weather conditions (tomatoes and snap beans), but was less active when applied to later season crops (pumpkins) planted when weather conditions were hot and dry.

Results from the two year studies were promising in many respects for the potential of this G. virens system as a biological control agent for weed control. A major constraint at this time is the need for additional formulation research to ensure consistent activity under a variety of field conditions. We found that environmental conditions at the time of and immediately after application greatly influence the level of weed control that can be obtained.

Further development and research with G. virens as a mycoherbicide will require input from private pest management companies and from governmental research support agencies focusing on the development of biological approaches to pest (weed) control.

Collaborators:

Stephen Weller

Purdue Univ.
IN 47907
David Kent

Kent Farms
IN 47923
Steve Bonny

Indiana SA Assoc.
IN 47906
K.G. Raghothama

Purdue Univ.
IN 47907
David Swaim

Swaim & Assoc.
IN 47933
Farah Heraux

Purdue Univ.
IN 47907