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Increase in Cabbage Yield by Fenamiphos Treatment of Uninfested and Heterodera schachtii-Infested Field Soils. G. S. Abawi, Associate Professor, Department of Plant Pathology, Cornell University, Geneva, NY 14456. W. F. Mai, Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Plant Dis. 67:1343-1346. Accepted for publication 14 June 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1343.

In field microplot tests, fenamiphos was broadcast onto cabbage field soils and incorporated into the top 812 cm at a rate of 6.7 kg a.i./ha. All insect and disease control measures were made according to recommendations for commercial use. In 1977, marketable heads of cabbage grown in soils infested with 0.7 and 12 eggs of Heterodera schachtii per gram of soil (damaging level = six to nine eggs) averaged 4.3 and 3 kg, respectively. Addition of fenamiphos to the same soils resulted in 23% (5.3 kg/head) and 73% (5.2 kg/head) increases in marketable head weight, respectively. Applications of fenamiphos did not significantly affect the final population of H. schachtii. The influence of fenamiphos on cabbage yield was minimal when field soils were pretreated with Telone C-17 at 374 L/ha or by autoclaving. Increase of cabbage yield by fenamiphos, however, occurred in field soils previously pasteurized for 30 min at 50 C. Intermediate increases with fenamiphos were also obtained in soils previously pasteurized at 60, 70, or 80 C. A similar effect on cabbage yield was obtained with aldicarb at 6.7 kg a.i./ha. Control of foliar insects by fenamiphos and aldicarb did not explain the observed increase in cabbage yield. Soil treatment with the miticide propargite, the nitrification inhibitor nitrapyrin, and the fungicide metalaxyl (selectively active against pythiaceous fungi) did not increase cabbage yield. These data indicate that higher yields of cabbage obtained by treating soil with fenamiphos or aldicarb are due to control of soilborne biological agent(s) other than plant-parasitic nematodes.