Effects of Fumigant and Nonfumigant Nematicides on Pratylenchus penetrans and Yield of Potato.

In 1984-85 metham-sodium and the combination of 1,3-dichloropropene plus aldicarb decreased (P = 0.05) soil population densities of Pratylenchus penetrans at planting, midseason, and at harvest relative to the untreated control. These treatments increased (P = 0.05) marketable potato tuber yield from 27% to 46% in 1984 and from 23% to 37% in 1985, as compared with the control. In 1984 oxamyl (10% granular and 24% liquid) applied immediately after planting increased (P = 0.05) only the total yield; oxamyl applied 2 weeks after planting failed to control P. penetrans and to increase total or marketable yields. Oxamyl (10 G) applied 2 weeks after planting decreased (P = 0.05) Pf. In 1985 oxamyl (10 G) reduced (P = 0.05) P. penetrans population densities at midseason and harvest, whereas oxamyl (24 L) reduced only harvest population densities. In 1985 neither formulation of oxamyl increased tuber yield.