'n Evaluering van die doeltreffendheid van verskillende nematisiede by die beheer van aalwurms op mielies met spesiale verwysing na die tydperk van doeltreffendheid

Abstract

This study was undertaken to evaluate the effectiveness of various nematicides in the control of nematodes on maize. Field trials were conducted in the districts of Ventersdorp (1982-83) and Sterkstroom (1983-84). In trying to achieve chemical control of Pratyl e nchus brachy= urus and P. z e ae , carbofuran, aminofuracarb , terbufos, car= bosulfan and aldicarb were compared to each other. A com= plete randomized block design was used for the layout of the two experiments. Counting of nematodes was done prior to treatment and at two intervals after planting, with a final counting eight weeks after planting . Other data col= lected were dry mass, number of plants/ha, rainfall, soil temperature and yield estimates. For the 1982-83 season a crop was yielded at the Ventersdorp trial, although it was severely influenced by drought. Yield results for the Sterkstroom trial (1983-84) could not be ob= tained, due to drought conditions. Most of the nematicides effectively controlled nematodes under existing conditions. No significant differences were shown between treated and un= treated plots when the final yield was determined. During the 1982-83 season a higher yield was obtained in all treated plots (except for those treated with carbosulfan) than in the untreated control plots. As the differences were not statis= tically significant, the cost of the nemati~ides was not re= covered and no economic profit could be shown. For the 1983- 84 trial at Sterkstroom a gaschromatographic study was con= ducted to determine the period of effectiveness of the carbo= furan treatment. More research is needed to determine at which level of nematode infestation the use of nematicides would become economically feasible.