BIOFUMIGATION WITH MUSTARD, CANOLA AND OILSEED RADISH AS AN ALTERNATIVE TO METAM SODIUM FOR CONTROL OF PINK ROOT AND WEEDS IN ONIONS

Deron Beck*1, Brad Geary2, Corey Ransom3, Terry Mcgonigle4, Brad Brown1 and Mike Thornton1 * 29603 U of I Lane, Parma, ID 83660. Office: (208) 722-6701, Ext 221, Fax: (208) 722-6708, E-mail: dbeck@uidaho.edu

Mustard, canola and oilseed radish green manure crops have been suggested as substitutes for commercial pesticides in controlling soil-borne pests of onions. These biofumigant crops release allelochemicals, including glucosinolates, into soil upon incorporation. The objective of this study was to determine if biofumigants have the potential to reduce the use of fumigants and herbicides by reducing pink root infection and weed germination. A split-plot design was used with fallow, metam sodium, “Sunrise” spring canola, “Ida-Gold” hot mustard and “Colonel” oilseed radish as the main plots. Weed control subplots consisted of a weedy check, low input herbicide, high input herbicide and hand weeded treatments. Weed control input level was the most significant factor affecting weed densities. The high herbicide input treatment provided significantly better weed control than the low input treatment. Onion yields were increased by hand weeding, low input herbicide and high input herbicide weed control treatments compared to the weedy check. The low and high input herbicide treatments had yields similar to the hand-weeded plots. Based on weed competition, lower onion yields were expected in the low input herbicide treatment compared to the high input treatment. Metam sodium significantly reduced mycorrhizae colonization of onion roots had no affect on yield. In contrast, biofumigants did not significantly affect mycorrhizae colonization or pink root infection, but tended to reduce onion yields. This yield reduction was probably due to poorer onion stands that were seen each year of the study. Plant residue from biofumigant incorporation may have caused trash to build up on the planter shoes or reduce soil-seed contact, thereby reducing germination.

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