Damage to melon (Cucumis melo L.) cv. Durango by Meloidogyne incognita in Southern California

The relationship between increasing Meloidogyne incognita inoculum density and the growth of melon plants in pots was well described by the Seinhorst model. The estimated tolerance level was not affected by the age of the plant at time of exposure to the nematodes, but minimum yields increased significantly when nematode inoculation was delayed until 2 weeks after seeding. Similarly, in field grown plants, melon fruit yields decreased with increasing pre-plant nematode levels. Tolerance levels estimated from the field study were one second stage juvenile (J2) per 200 g soil sampled before planting, and the estimated yield loss at high nematode densities was 65%. The yield loss resulted primarily from fewer fruits being harvested per plant, rather than from the fruits being smaller. This may be due to a redirection of plant nutrients towards sustaining the nematodes developing in the root systems, inhibiting fruit set. The results indicate that preventing immediate access of the nematodes to very young seedlings may prevent severe yield losses, but may also result in high populations at harvest.