Diseases of melon (
Root-knot nematode
Root-knot nematode, Meloidogyne incognita, infects all varieties of melons and many other plants. This nematode is widespread in Arizona, but is usually found in sandy or sandy loam soils. It is an obligate parasite that must complete its life cycle in a plant host, but eggs are persistent and can remain inactive in the absence of a host and/or fallow for months or years.
As M. incognita larvae enter the plant root, feed and mature, the surrounding cells of the plant root increase in size and divide causing swellings, often referred to as galls, on the roots. The flow of nutrient and water is restricted, and plants wilt quickly when water becomes limiting. If plants are infected when young, they are often severely stunted and chlorotic. Infected vines rarely die, but are generally not productive.
Because of its wide host range, control of root knot nematode is difficult. Cotton, sorghum, corn, and beans, among many other crops, are all hosts and should not be rotated with melons when M. incognita is a problem. Rotations to alfalfa and oats, which are not hosts, are effective, especially in multiple year rotations. Preplant soil fumigation with 1,3 dichloropropene or metam-sodium (Vapam) is also effective in reducing early infections. Soil solarization is an option for small areas that can be effectively tarped for at least 6 weeks in summer. More information on control strategies and solarization can be obtained from:
http://cals.arizona.edu/yavapai/anr/hort/byg/archive/soilsolarization.html
and
http://edis.ifas.ufl.edu/pdffiles/CV/CV11200.pdf
March 3, 2009