Attraction of northern false chinch bugNysius niger (Heteroptera: Lygaeidae) to mustard oils

Selected isothiocyanates (mustard oils) were tested as attractants for adultNysius niger Baker, a pest of mustard crops in the Canadian prairies. Individuals of both sexes, but predominantly females, were caught in yellow boll-weevil traps baited with certain mustard oils. Initial testing was done with compounds loaded on rubber septa, a procedure that resulted in a great disparity in release rates between compounds due to differences in volatility. In subsequent experiments, glass tubes of varying dimensions were used so that release rates of each compound could be controlled and maintained at a constant rate. Of mustard oils tested, ethyl 4-isothiocyanatobutyrate, the corresponding methyl ester of which is found in seeds in the cruciferous genusErysimum, was the most attractive. However, the methyl ester itself was either less attractive or not attractive at all. Allyl andn-propyl isothiocyanates were less attractive than ethyl 4-isothiocyanatobutyrate, and 2-phenylethyl isothiocyanate was not attractive. Insects were caught in traps almost exclusively when traps were in proximity to canola and mustard fields in bloom.