Management of root-knot nematodes with resistant cotton cv. NemX

Root-knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] is a serious pest of cotton (Gossypium hirsutum L.) and many crops worldwide. R ecent banning of most nematicides has increased the need for development of nematode resistant crop cultivars, such as NemX cotton, which was released in California in 1995. This study was conducted to determine the effective ness of NemX in suppressing populations of M. incognita and protecting susc eptible crops grown in rotation with it. NemX was grown in rotation with su sceptible cotton cvs, Maxxa and Pima S7, susceptible lima bean (Phaseolus l unatus L. cv, Henderson), and resistant cowpea [Vigna unguiculata (L.) Walp , cv, CB 88] and alfalfa (Medicago sativa L, cv, WL525HQ). The experiments were done at Shafter, CA, during 1994-1996 on plots with sandy loam soil an d natural infestation of M. incognita rare 3, NemX suppressed nematode popu lations strongly in all treatments and one planting was as effective as two successive ones. Lint yield of NemX averaged 1000 kg ha(-1), irrespective of preplant nematode density (Pi). In contrast, yields of susceptible Maxxa cotton varied indirectly with nematode Pi and ranged from 530 to 1360 kg h a(-1). NemX and resistant cowpea or alfalfa had shout equal effectiveness i n suppressing nematode population density in soil and in protecting a subse quent susceptible crop. Since different species of root-knot nematode attac k many crops and M. incognita is the only species that reproduces well In c otton, utilization of NemX will greatly enhance the rotational value of rot ten for managing the nematodes.