Effects of Rapeseed Meal Soil Amendments on Microsclerotia of Cylindrocladium crotalariae in Naturally-Infested Soil1

Abstract

Abstract Cylindrocladium black rot (CBR) of peanut, caused by Cylindrocladium crotalariae, is most often controlled through the use of metham sodium (Vapam), a commercial soil fumigant. Several plant species, including rape, produce glucosinolates which decompose to form isothiocyanates which are closely related to methyl isothiocyanate the active ingredient of metham sodium. Such plants may be useful in CBR control strategies. This research was conducted to determine the fungicidal effect of the glucosinolate in rapeseed meal on microsclerotia of C. crotalariae. Rapeseed meal containing 13 mmol of glucosinolate kg-1 was added to a soil column 50 mm in diameter and 325 mm long. Meal was either placed at the 150 mm depth or mixed with the top 150 mm of soil. An untreated control and metham sodium at a rate equivalent to 190 L ha-1 injected 150 mm deep were included. Metham sodium was much more effective in reducing microsclerotial populations of C. crotalariae than rapeseed meal. However, the amount of glucosinolate in the metham sodium treatment was three times as great as that found in the rapeseed meal. Rapeseed meal treatments usually significantly reduced the number of soilborne microsclerotia when comparisons were made with untreated soil.