Trichoderma virens-inoculated composted chicken manure for biological weedcontrol

The fungus Trichoderma (Gliocladium) virens produces a broad spectrum of an tibiotic compounds, including the phytotoxin viridiol. However, to be used as a mycoherbicide, an economical substrate must be developed that supports the growth of the fungus and production of viridiol. Composted chicken man ure (CCM) is an abundant, renewable resource that could serve as a substrat e for held delivery of T. virens for weed control. This research investigat ed the conditions necessary for the production and stabilization of viridio l, mycoherbicidal activity of viridiol, and production of viridiol on a CCM substrate. Although produced at basic pH, viridiol was more phytotoxic at acidic pH. The EC50 Of viridiol for inhibition of seed germination of Setar ia viridis and Amaranthus retroflexus was 312 and 764 mu M, respectively. T he EC50 of viridiol for the inhibition of root growth of S. viridis and A. retroflexus roots was 56.3 and 1.3 mu M, respectively. Growth of T. virens and production of viridiol up to 170 mu g/g were supported on a CCM substra te supplemented with nutrients. Viridiol production was detected 10 days af ter incorporation into field soil. In greenhouse tests, T. virens-inoculate d CCM medium mixed with field soil reduced weed emergence and weed dry weig ht 77 and 68%, respectively, 8 weeks after incorporation compared to contro ls. In conclusion, CCM supported T. virens growth and viridiol production a t levels capable of controlling weed emergence and growth in greenhouse tri als. (C) 1999 Academic Press.