Forty cotton (Gossyium spp.) varieties or breeding lines close to release were planted in a field infested with the Reniform nematode (Rotylenchulus reniformis). Plots were two 40-ft rows. Experimental design was a RCB with five replications. Factoral treatments (40x2) consisted of the cotton varieties with and without Temik 15G at 6 lb/A. The plots which were not treated with Temik received 10 lb/A of Terraclor Super X + Disyston (6.5 + 1.63 + 6.5 G); the Temik treated plots received 10 lb/A of Terraclor Super X (10 + 2.5 G). Disyston was included for early season insect control but has little nematode activity. All treatments were applied in-furrow at planting. All plots were treated for early insect control. Reniform nematode counts were taken Apr 19 (at planting), Jun 15, Aug 5, and Oct 4. The experiment was harvested on Oct 4 with a commercial picker adapted for plot harvesting.

No significant differences in reniform nematode numbers were found among the 40 varieties on any of the sampling dates. Therefore, none of the varieties were resistant. Nematicide treatment had a significant (P = 0.05) effect on reniform nematode counts only on the second sampling date. Averaged across cotton genotypes, Temik increased yields by 7.6%. Yield increases of individual varieties in response to Temik ranged from 2.8% to 21.1%. `Holly 147', `DP 51', `DES 119', `CB 1233', `SG 125', `ST 453', `GC 9033', `GC 210', `SG 501', and `Holly 133' yielded significantly higher than treated with Temik. Several high yielding varieties had no significant yield increases with nematicide treatment. This lack of yield increase indicates that there may be some tolerance to this nematode within the varieties evaluated.