Effects of oxamyl on the reproduction of Meloidogyne hapla and Heterodera schachtii.

Veech (7) reported that dif lubenzuron had ovicidal activity against Meloidogyne incognita and suggested that this activity could be impor tan t in developing new control strategies. Radewald et al. (5) and Birchfield (1) respectively provided prel iminary evidence that oxamyl suppresses reproduct ion of M. incognita and Rotylenchulus reniformis. This study was conducted to determine the effects of oxamyl on the reproduct ion of Meloidogyne hapla Chitwood 1949, and Heterodera schachtii Schmidt 1871, and to determine the impact of t ime of appl icat ion on the control of M. hapla and H. sehachtii. Three-week-old lettuce (Lactuca sativa L. cv ' I thaca ' ) seedlings in 10-cm-diam pots of autoclaved organic soil (Carlisle muck) were inoculated with 6,800 M. hapla eggs. Similarly, 5-week-old table beet (Beta vulgaris L. cv 'Ruby Queen ') seedlings in 10-cm-diam pots of autoclaved sandy loam soil were inoculated with 6,000 H. schachtii larvae. Beginning at the t ime of inoculat ion or 1 week after inoculation, the lettuce and beet seedlings each received two foliar applications of oxamyl (methyl N,Ndimethyl-N[(methylcarbamoyl)oxy]1thiooxamimidate) at 2-week intervals at a rate of 4.8 g a.i . / l i ter. Dur ing appl icat ion of oxamyl the pots were placed on their sides and the surface covered with a luminum foil to prevent contaminat ion of the soil. T h e seedlings were sprayed to run-off, left in the horizontal position until the foliage had dried, and then placed in controlledenvi ronment chambers at 25 C with a 14-1i photoper iod (26,900 ix). Lettuce plants were harvested six weeks after i lmculation and the root-gall index was determined on a ra t ing system of 0 = nogal l ing ; 1 = 1 1 0 % ; 2 = 11-25%; 3 = 26-50%; 4 = 51-75%; and 5 = 76-100% of the roots galled. T h e reproduct ion of M.