Differential effect of nematicide treatments on tuber yields in early- andlate-maturing potato cultivars

A 3-year field study examined the effects of 1,3-dichloropropene or oxamyl on tuber yields in four early- and five late-maturing potato cultivars. The nematicide treatments increased total tuber yield by approximate to 12% fo r early-maturing cultivars, but by less than 2% for the late-maturing culti vars. The treatments reduced the numbers of root lesion nematodes (primaril y Pratylenchus penetrans), which were the dominant plant parasitic nematode s at the site. Covariance analysis indicated that treatment effects on tota l tuber yield were no longer significant after adjusting for root lesion ne matodes in soil at harvest, confirming that these nematodes had a direct ef fect on the host. As expected, there were significant inverse relationships (P = 0.05) between total tuber yields and numbers of root lesion nematodes in soil and in roots. However, the application of nematicides in late-matu ring cultivars was found to be of no practical value. Crop production syste ms designed to reduce or optimize pesticide applications can form one crite rion in the development of more environmentally sensitive management strate gies. The merit of utilizing chemicals for root lesion nematode control are considered with regard to cultivar maturity.