Effects of a resistant corn hybrid and fenamiphos on Meloidogyne incognita in a corn-squash rotation

The efficacy of a double-cross corn (Zea mays) hybrid (Old Raccoon selection X T216) X (Tebeau selection X Mp 307) resistant to Meloidogyne incognita as a rotational crop, and fenamiphos treatment for management of root-knot nematode (M. incognita race 1) in squash (Cucurbita pepo var. melopepo) was evaluated in field tests during 1996 and 1997. Numbers of M. incognita in the soil and root-gall indices were lower on the resistant hybrid than on a commercial cultivar DeKalb DK-683. Treatment means across both corn entries had lower root-gall indices following fenamiphos treatment. In soil collected 2 September 1997, there were more colon-forming units (cfu) per gram of oven-dried soil of Pythium spp. from plots planted to DK-683 treated with fenamiphos than in untreated plots (88 vs. 59 cfu). Some corn plots had individual plants with 10% to 15% of the crown and brace roots decayed, but no differences due to fenamiphos treatment. Lodging of stalks was 40% to 50% more in the double-cross hybrid than in DK-683. Yield was greater from DK-683 than the double-cross hybrid. Based on cultivar means across fenamiphos treatments and fenamiphos treatment means across cultivars, root-gall indices and yield of squash were significantly lower following the double cross hybrid than DK-683 and in fenamiphos-treated plots than in untreated plots of squash. Yield of squash was not affected by at-planting treatment with fenamiphos on the preceding crops of corn. Nematode resistance must be transferred into the elite materials of commercial seed companies to reach its full potential as a nematode management strategy.