Nematode Management in Cotton

The five most important cotton-producing countries are China, United States, India, Pakistan, and Brazil. There are many other important cotton producing regions in Asia, Australia, Africa and the Americas. Cotton is grown entirely in tropical, subtropical, and warm-temperature climates, and the major nematodes of cotton are well adapted to warm environments. Globally, the most damaging nematodes of cotton are Meloidogyne incognita races 3 and 4 and Rotylenchulus reniformis. These nematodes are of concern in the United States, India, Pakistan, Egypt and Brazil. Additional nematodes of major importance in relatively restricted areas include Hoplolaimus columbus and Belonolaimus longicaudatus in the southeastern United States and Pratylenchus brachyurus in Brazil.Meloidogyne incognitafrequently is involved in a cotton disease complex with Fusarium wilt that has far more impact on the crop than the nematode or the fungus alone. Until very recently, the primary strategies used for nematode management in cotton have been the application of fumigants and cholinesterase inhibitors, rotation with Zea mays, Arachis hypogaea or Glycine max and incorporation of soil amendments. The primary concern over P. brachyurus in Brazil is its potential to damage Z. mays or G. max grown in rotation with cotton. Promising seed treatments containing avermectin or harpin proteins have recently become available. Several cultivars resistant to Melodogyne incognita races 3 and 4 have been released. Currently there is intense research toward the introgression of resistance to R. reniformis into upland cotton, Gossypium hirsutum from other Gossypium species. During the last two years DNA markers for major genes for resistance to Meloidogyne incognita and Rotylenchulus reniformis have been discovered in upland cotton and offer great potential in the development of resistant cultivars suitable for the wide range of growing conditions where cotton is produced.