Survey of Plant Parasitic Nematodes Associated with Virginia Cotton Production

Plant parasitic nematodes limit yield potential of cotton throughout production areas including those in Virginia. Efficacy of and need for nematode management strategies, including host resistance, rotation, biological control, and chemical control, depends on the type and numbers of nematodes present. Thus, an assessment of parasitic nematodes associated with cotton in Virginia and their distribution is needed as a basis for making management recommendations. A survey of fields in the cotton-growing region of southeastern Virginia was initiated in 2015 and will be continued for a minimum of three years. In 2015, 86 fields from throughout the cotton growing counties of Virginia were sampled in late summer/early fall prior to harvest. Each sample was a composite of soil cores taken at a 6-in. depth in a zig-zag pattern from across approximately 10 acres. Sampled fields varied in current crop planted (cotton, soybean, or peanut) but all have cotton in the rotation. Overall, 38% (N=33) of sampled fields were at low risk for damage to the cotton crop from nematodes, 21% (N=18) had moderate risk, and 41% (N=35) had high risk. Twenty-four percent of fields sampled had stubby root numbers indicating high risk for damage to cotton. Southern root-knot nematode is considered one of the most economically important nematodes for cotton, but only 2% of the fields sampled had either moderate or high populations, and root-knot nematode was found in only 26% of fields overall. Though lesion and lance nematodes were present in many fields, less than 10% of fields had numbers sufficient to impact the cotton crop. Sting nematode was found in 16% (N=14) of sampled fields, and this nematode can be highly damaging even at low numbers. Additional samples are being collected during the 2016 field season. The impact of plant parasitic nematode populations on Virginia cotton will be discussed.