Cotton variety evaluation with and without Velum Total for root-knot management in south Alabama, 2016

摘要

Ten cotton varieties were evaluated along with Velum Total for control of the root-knot nematode at the Gulf Coast Research and Extension Center near Fairhope, Alabama. The field was artificially inoculated with root-knot nematode in 2013 and inoculation has been repeated in subsequent years. A control field of the same ten varieties was also planted in an adjacent field that is absent of root-knot nematode. The soil is a Malbis sandy loam, which contains 59% sand, 31% silt, 10% clay. The root-knot field trial was installed as a split plot design (variety and nematicide treatments) with five replications. Plots were planted on 12 May, and consisted of 4 rows, 25 feet long with 36-inch row spacing and 20-foot-wide alleys. Seed varieties contained standard seed treatment as sold based upon variety, and Velum Total was applied in-furrow to two rows in each plot with 8002 flat fan nozzles angled diagonally across the seed furrow at a rate of 14 oz/acre. The other two rows were left untreated. Seed wasplanted at a 1-inch depth. The control field consisted of 2-row plots arranged in a randomized complete block design replicated five times. All plots were maintained as recommended by the Alabama Cooperative Extension System with typical pesticide and fertility production practices, and an overhead irrigation system was used for watering as needed. Nematode densities were measured in the root-knot field at 46 days after planting (DAP) by digging up four random samples for both treated and untreated rows. Nematodes were extracted from the cotton roots using 6% NaOCl and collected on a 25 um sieve. Plots were harvested on 31 Oct, and data were subjected to analysis of variance in SAS 9.4 (SAS Institute Inc.) using the PROC GLIMMIX procedure and means compared using Tukey-Kramer with P < 0.10. Monthly average maximum temperatures from planting to harvest (May through Oct) were 82.7, 88.9, 90.1, 89.2, 88.7, and 83.4°F with average minimum temperatures of 63.9, 71.1, 74.8, 74.2, 70.7, and 58.3°F, respectively. Rainfall accumulation for each month was 2.31, 3.39, 2.91, 3.95, 0.00, and 0.00 in. respectively, with a total of 12.56 in. over the entire growing season.