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Nematodes pose a serious threat to cotton production in South Carolina. Each year nematodes claim over 5% of the possible cotton production in South Carolina. Not every field is infested with damaging levels of nematodes. But, in the fields that are infested, yield losses probably range from barely detectable to over 50%. Over 90% of South Carolina cotton fields have at least one species of nematodes present in the field. Almost half of all fields have at least one of the species over damage threshold levels. Columbia lance nematode is the primary nematode pest in all areas of the state being present in almost 40% of all fields at damaging levels. The incidence of fields with either root-knot or reniform nematodes at damaging levels is much lower. Root-knot appears to be more severe in the Savannah Valley area, whereas reniform nematode is more severe in the Pee Dee region and has not been found in Aiken, Allendale, Bamberg, Barnwell, or Hampton counties.
Management tools for any of the three nematode species are limited. Use of deep tillage of some sort is useful in helping with managing all three species. Management tactics by species are as follows.
Columbia lance nematode management relies heavily on the use of nematicides. There are no resistant or tolerant cultivars available. Crop rotation is of limited value in South Carolina since corn and soybeans are hosts. Peanut is a good nonhost, however limited acreage in South Carolina makes this option limited in application. Many weeds are hosts for Columbia lance nematode making the fallowing of fields ineffective as a rotation strategy. The effects of planting date are unknown. Conservation tillage practices in general have little effect on Columbia lance nematode as long as some form of deep tillage is maintained. Most winter cover crops are hosts of this nematode and may increase populations of Columbia lance nematodes if the cover crop is planted prior to November and harvested after March. Cover crops planted after October and harvested prior to April will probably not affect nematode numbers since the nematode is inactive at low soil temperatures.
Root-knot nematode management is very similar to that of Columbia lance nematode in that it relies heavily on the use of nematicides. There are no resistant or tolerant cultivars available. Cultivars advertised as root-knot nematode or “nematode” resistant are usually resistant only to the Fusarium wilt-root-knot nematode complex. Stoneville’s LA 887 does exhibit partial resistance to root-knot nematode, but it will still respond to the application of a nematicide in most root-knot nematode infested fields. Damage from the wilt fungus is rarely seen on modern cultivars, but even low levels of root-knot nematode can cause two severe yield losses on these cultivars. Crop rotation is of limited value in controlling root-knot nematode in South Carolina. Root-knot nematode will survive or build on corn without damaging the corn. Many soybean cultivars are resistant to root-knot nematode, however the widespread distribution of Columbia lance nematode limits this rotation since Columbia lance is very damaging to most soybean cultivars and most growers do not survey their fields. Peanut is a good nonhost, however limited acreage in South Carolina restricts this option. Many weeds are hosts for root-knot nematode making the fallowing of fields ineffective as a rotation strategy. The effects of planting date are unknown. Conservation tillage practices in general have little effect on root-knot nematode as long as some form of deep tillage is maintained. With the exception of ‘Cahaba’ vetch, most of legume winter cover crops are hosts of root-knot nematode and may increase populations if the cover crop is planted prior to November and harvested after March. Cover crops planted after October and harvested prior to April will probably not affect nematode numbers since the nematode is inactive at low soil temperatures. Rye may help decrease root-knot nematode numbers, however this is not well documented at the present time.
Reniform nematode management also relies heavily on nematicides. Reniform nematode is relatively new and very little data exists on its management compared to root-knot or Columbia lance nematodes. Resistance or tolerance to reniform nematode has not been well documented in commercially available cultivars. Some cultivars such as Stoneville’s LA 887 may be partially tolerant to reniform nematode, however, it will still respond to the application of a nematicide. Crop rotation is possible as a management tool as corn, grain sorghum, and some soybean cultivars are resistant. See the Cotton Nematode Control Guide for rates of nematicides for controlling either Columbia lance, root-knot or reniform nematodes. Also observe the following guidelines.