|Lawrence, Kathy -|
|Moore, Scott -|
|Durbin, Bobby -|
Submitted to: Cotton Research and Extension Report
Publication Type: Experiment Station
Publication Acceptance Date: February 15, 2009
Publication Date: March 15, 2009
Citation: Lawrence, K.S., Moore, S.R., Balkcom, K.S., Durbin, B. 2009. Cotton Cultivar Response to Root-Knot Nematodes in Two Tillage Regimes, 2008. 2008 Cotton Research and Extension Report. No. 33. p. 74. Technical Abstract: Six cotton cultivars were evaluated for yield response to the root-knot nematode in a naturally infested field at E. V. Smith Research and Extension Center, near Shorter, Alabama. The field had a long history of root-knot nematode infestation, and the soil type was classified as a sandy loam. Plots consisted of four rows, 50 feet long with 36-inch row spacing, and were planted in a factorial arrangement with five replications. Convention tillage and no tillage were the main factors and cotton cultivar was the sub factor with plots split with and without nematicide. Avicta amd Cruiser was applied to the seed by the manufacturer. Temik 15G (5 pounds per acre) was applied at planting on May 23 in the seed furrow with chemical granular applicators attached to the planter. All plots were maintained throughout the season with standard herbicide, insecticide, and fertility production practices as recommended by the Alabama Cooperative Extension System. Population densities of the root knot nematodes were determined at mid-seasons after a significant rainfall event. Ten soil cores, 1 inch in diameter and 6 inches deep, were collected from the two rows of each plot in a systematic sampling pattern. Nematodes were extracted using the gravity sieving and sucrose centrifugation technique. Plant height and nodes per plant were also recorded at this time. Plots were harvested on October 22. Data were statistically analyzed by GLM and means compared using Fisher’s protected least significant difference test (P = '0.10). Monthly average maximum temperatures for May through September were 84.5, 93.6, 92.5, 89.7, and 86.7 degrees F with average minimum temperatures of 60.9, 68.2, 70.0, 71.1, and 66.0 degrees F, respectively. Rainfall accumulation for each month was 2.52, 1.98, 4.97, 9.92, and 0.73 inches with a total of 20.1 inches. Rainfall was a limiting factor in the 2008 season; thus, rootknot nematode pressure was moderate under these conditions. Only 20 inches of rain were recorded for the entire growing season. At planting, root-knot nematode numbers averaged 51 J2’s per 150 cm3 of soil. Interactions between cultivar, tillage, and nematicide were observed for plant height and nodes per plant. Root-knot numbers of J2 from the soil varied between varieties with the lowest numbers observed in DPL 117, STM, and ST 5599. Over all cultivars, no tillage plots contained higher numbers of root-knot nematodes than conventionally tilled plots. Nematicide application did not consistently reduce rootknot numbers across cultivars. Seed cotton yields averaged 3708 pounds per acre across all cultivars with ST 5599 and STM producing a greater yield (P = 0.01) than DPL 555, DPL 515, DPL 117, and DPL 143. Nematicide and tillage did not affect seed cotton yields (P = 0.01).