Sandy Steckel

Thrips are one of the most ubiquitous pests of cotton in Tennessee. Adult and immature thrips injure seedling cotton by puncturing leaf cells and feeding on the contents. Injury may cause leaf deformity, stunting, and delays in maturity. Severe, prolonged infestations may cause stand loss and plant death. Preventative at-planting insecticide seed treatments and/or in-furrow insecticides are recommended. However, a foliar treatment may also be needed in high-pressure situations or when abiotic stressors cause delayed plant growth. Selected insecticides were evaluated for control of thrips spp. in seedling cotton at the Research and Education Center at Milan, TN. Cotton was planted on 3 June. The test was arranged in an RCB design with 4 replicates. Individual plots were 13.3 × 30 ft and planted at a rate of 4 seeds per row ft on 40-inch row spacing. Treatments were applied with a CO₂ backpack sprayer calibrated to deliver 9.7 gpa with 8001 flat fan nozzles at 40 psi. The foliar application was made on 13 June to cotton with one true leaf, and high thrips numbers were present. Insects were sampled by cutting 5 random plants near the soil level and immediately placing in a 70% isopropyl alcohol solution. Samples were taken to the lab and individual plants were washed with a fresh alcohol solution. Each sample was sieved through a 150-µm sieve, and immature and adult thrips were counted using a dissecting microscope. Thrips control was evaluated 15 June, 2 days after the initial application (2 DAT) and 21 June (8 DAT). Thrips injury ratings were determined 21 June (8 DAT) by examining whole plots using a 0–5 scale with 0 = no injury and 5 = plant death. Yield data were collected 2 November by harvesting the 2 center rows of each plot with a spindle picker modified for this purpose. Data were subjected to ANOVA and an F-protected least significant difference (LSD, P < 0.05) was used to distinguish treatment mean differences.

Twospotted spider mites (TSSM) are occasional pests of cotton in Tennessee, most often occurring when weather conditions are very hot and dry and when insecticide applications have reduced populations of beneficial arthropods. Spider mites reduce the plant’s ability to produce photosynthate and can cause premature defoliation, stunting, and yield loss. Selected miticides and the herbicide Liberty (AI, glufosinate) were evaluated for control of a TSSM infestation on cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 2 May on a 38-inch row spacing. The test was arranged in an RCB design with 4 replicates. Individual plots were 12.7 × 40 ft. Treatments were applied with a high clearance sprayer with a compressed air system calibrated to deliver 9.4 gpa with 8001 flat fan nozzles. A foliar application was made on 19 July to flowering cotton with a spider mite infestation well in excess of the recommended treatment threshold of 30–50% of plants showing injury with mites present. Adult and immature TSSM were counted on the abaxial leaf side using a 1-inch² hand lens. Ten leaf samples were collected from the center 2 rows of all plots. TSSM were counted 3 and 6 days after treatment (DAT). Data were subjected to ANOVA, and Fisher’s Protected Least Significant Difference (P ≤ 0.05) was used to distinguish treatment mean differences.

Tarnished plant bug is consistently the most destructive insect pest in Tennessee cotton. Plinazolin, a new insecticide, and other selected foliar insecticides were evaluated for control of plant bugs in ThryvOn cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 19 May. The test was arranged in an RCB design with 4 replicates. Individual plots were 12.7 × 40 ft and planted at a rate of 4 seeds per row ft on 38-inch centers. Treatments were applied with a high clearance sprayer using a compressed air system calibrated to deliver 9.4 gpa with 8001 flat fan nozzles. The foliar application was made 3 August to flowering cotton with a plant bug infestation well in excess of the recommended treatment threshold of 6 plant bugs per 10 row feet. Plots were sampled with a standard 2.5 × 2.5 ft black cloth shake sheet by placing the sheet between 2 rows and vigorously shaking plants to dislodge insects. On each date, 2 shake sheet samples were taken on the center 2 rows (10 row ft total) of all plots. Plant bug control was evaluated 8 August, 5 days after initial application (5 DAT), 12 August (9 DAT), and 19 August (16 DAT). Data were subjected to analysis of variance, and an F-protected least significant difference (P < 0.05) was used to distinguish treatment mean differences.

Tarnished plant bug is consistently the most destructive insect pest in Tennessee cotton. Tarnished plant bug has a history of developing resistance to insecticides, and ongoing evaluations are needed to verify the continued effectiveness of labeled materials and to test new products. Plinazolin, a new insecticide, was compared with selected labeled insecticides to evaluate its control of plant bugs in cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 31 May. The test was arranged in an RCB design with 4 replicates. Individual plots were 12.7 × 40 ft and planted at a rate of 4 seeds per row ft on 38-inch row spacing. Treatments were applied with a high clearance sprayer using a compressed air system calibrated to deliver 9.4 gpa with 8001 flat fan nozzles. The foliar application was made 8 August to flowering cotton with a plant bug infestation well in excess of the recommended treatment threshold of 6 plant bugs per ten row feet. Plots were sampled with a standard 2.5 × 2.5 ft black cloth shake sheet by placing the sheet between 2 rows and vigorously shaking plants to dislodge insects. On each date, 2 shake sheet samples were taken on the center 2 rows (10 row ft total) of all plots. Plant bug control was evaluated 11 August, 3 days after initial application (3 DAT), 16 August (8 DAT), and 23 August (15 DAT). Yield was taken 13 October by harvesting the 2 center rows with a spindle picker modified to collect data for small plots. Data were subjected to analysis of variance, and an F-protected least significant difference (P < 0.05) was used to distinguish treatment mean differences.

Thrips are one of the most ubiquitous pests of cotton in Tennessee. Adult and immature thrips injure seedling cotton by puncturing leaf cells and feeding on the contents. Injury may cause leaf deformity, stunting, and delays in maturity. Severe, prolonged infestations may cause stand loss and plant death. Preventative at-planting insecticide seed treatments and/or in-furrow insecticides are recommended. At-planting insecticide applications were evaluated for control of thrips spp. in seedling cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 31 May. The test was arranged in an RCB design with 4 replicates. Individual plots were 12.7 × 35 ft and planted at a rate of 4 seeds per row ft on 38-inch centers. Granular treatments were applied with standard insecticide boxes mounted on a cone planter delivering product into the open furrow. In-furrow spray treatments were applied using a compressed CO₂-charged spray system calibrated to deliver 8.2 gpa with 80015 flat fan nozzles spraying across the open furrow in front of the closing wheels. Insects were sampled by cutting 5 random plants near the soil level and immediately placing in a 70% isopropyl alcohol solution. Samples were taken to the laboratory, and individual plants were washed with a fresh alcohol solution. Each sample was sieved through a 150-µm sieve, and immature and adult thrips were counted using a dissecting microscope. Thrips control was evaluated 14 and 20 d after planting (DAP). Thrips injury ratings were determined 15 and 20 DAP by examining whole plots using a 0–5 scale with 0 = no injury and 5 = plant death. Yield data were collected 13 October by harvesting the 2 center rows of each plot with a spindle picker modified for this purpose. Data were subjected to analysis of variance, and Fisher’s protected least significant difference (P ≤ 0.05) was used to distinguish treatment mean differences.

Tarnished plant bug is consistently the most destructive insect pest in Tennessee cotton. Control of plant bugs in cotton with selected foliar insecticides was evaluated at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 31 May. The test was arranged in an RCB design with 4 replicates. Individual plots were 12.7 × 35 ft and planted at a rate of 4 seeds per row ft on 38-inch row spacing. Treatments were applied with a high clearance sprayer using a compressed air system calibrated to deliver 9.4 gpa with 8001 flat fan nozzles. The foliar application was made 3 August to flowering cotton with a plant bug infestation well in excess of the recommended treatment threshold of 6 plant bugs per 10 row feet. A heavy (2.6 inch) rainfall event occurred just 7 h after the application. Though some insect control was observed (50–81% compared with the untreated), a sequential application was made 9 August as plant bug densities for all treatments were above threshold after sampling. Plots were sampled with a standard 2.5 × 2.5 ft black cloth shake sheet by placing the sheet between 2 rows and vigorously shaking plants to dislodge insects. On each date, 2 shake sheet samples were taken on the center 2 rows (10 row ft total) of all plots. Plant bug control was evaluated 8 August, 5 days after initial application (5 DAT1), 12 August, 3 days after the second application (3 DAT2), and 17 August (8 DAT2). Yield was taken 10 October by harvesting the 2 center rows with a spindle picker modified to collect data for small plots. Data were subjected to ANOVA, and Fishers protected least significant difference (LSD, P < 0.05) was used to distinguish treatment mean differences.

Selected insecticide treatments were evaluated for control of cotton aphid in cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 12 June. The test was arranged in an RCB design with four replicates. Individual plots were 12.67 × 35 ft and planted at a rate of four seeds per row ft on 38-inch row spacing. Treatments were applied with a high clearance sprayer calibrated to deliver 9.2 GPA at 40 PSI with 8001 flat fan nozzles. Insecticide treatments were applied 12 August to flowering cotton when aphid populations were present. Post-treatment aphid counts were taken 17 and 21 August, 5 and 9 DAT, respectively. To estimate cotton aphid density, leaves located three to four nodes below the uppermost node were selected from random plants in the center two rows, and aphid numbers were recorded. Data were subjected to ANOVA, and means were separated using Fisher’s protected least significant difference (P ≤ 0.05). To normalize the data distribution, Aphis gossypii counts made 9 DAT were square root (x + 0.5) transformed prior to analysis. Nontransformed means are presented ( Table 1).

Selected insecticides were evaluated for control of thrips spp. in seedling cotton at the Research and Education Center at Milan, TN. Cotton was planted on 21 May. The test was arranged in an RCB design with four replicates. Individual plots were 13.3 × 30 ft and planted at a rate of four seeds per row ft on 40-inch row spacing. Treatments were applied with a high clearance sprayer calibrated to deliver 9.2 GPA at 40 PSI with 8001 flat fan nozzles. The first application was made 5 June to cotton with one true leaf and high thrips numbers present. A second application was made 11 June as populations in plots for all treatments exceeded five thrips per plant, and there were obvious signs of injury on emerging leaves. Insects were sampled by cutting five random plants near the soil level and immediately placing in a 70% isopropyl alcohol solution. Samples were taken to the lab, and individual plants were washed with fresh alcohol solution. Each sample was sieved through a 150-µm sieve, and immature and adult thrips were counted using a dissecting microscope. Thrips control was evaluated 8 June, 3 d after the initial application (3 DAT1) and 15 June (4 DAT2). Additionally, thrips injury ratings were determined 10 June (5 DAT1), 14 June (3 DAT2), and 18 June (7 DAT2) by examining whole plots using a 0–5 scale with 0 = no injury and 5 = plant death. However, only injury data from the final evaluation will be presented. Yield was taken 9 November by harvesting the two center rows of each plot with a spindle picker modified for this purpose. Counts of immature thrips and total thrips at 4 DAT2 were log transformed (x + 1) prior to the ANOVA, and Fisher’s protected least significant difference (P ≤ 0.05) was used to distinguish treatment mean differences. Nontransformed means are presented in Table 1.

Selected insecticide treatments were evaluated for control of cotton aphid in cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 9 May. The test was arranged in an RCB design with four replicates. Individual plots were 12.67 × 35 ft and planted at a rate of four seeds per row ft on 38-inch row spacing. Treatments were applied with a high clearance sprayer calibrated to deliver 9.2 gpa at 40 psi with 8001 flat fan nozzles. Insecticide treatments were applied 27 Jul to flowering cotton when aphid populations were present. Treatments were evaluated by counting the number of cotton aphids from 10 leaves per plot. Leaves located 3–4 nodes below the uppermost node were selected from the center two rows on 31 Jul, 4 d after application (4 DAT) and 3 Aug (7 DAT). Aphid numbers for the 4 DAT sample were log transformed (x + 1) prior to the ANOVA and an F-protected Least Significant Difference (LSD, P < 0.05) was used to distinguish treatment mean differences. Nontransformed means are presented in the table.

Selected insecticides, alone or in tank-mixtures, were evaluated for control of tarnished and clouded plant bugs in cotton at the West Tennessee Research and Education Center at Jackson, TN. Cotton was planted on 16 May 2017. The test was arranged in an RCB design with four replicates. Individual plots were 12.67 × 40 ft and planted at a rate of 4 seeds per row ft on 38-inch row spacing. Treatments were applied with a high clearance sprayer calibrated to deliver 9.2 gpa at 40 psi with 8001 flat fan nozzles. The first application was made 24 Jul (Appl 1) to flowering cotton when plant bugs exceeded the economic threshold of six plant bugs per ten row feet. A second application was made (7 Aug, Appl 2) as populations in most treated plots again exceeded this threshold. Plots were sampled with a standard 2.5- × 2.5-ft black cloth shake sheet by placing the sheet between two rows and vigorously shaking plants to dislodge insects. On each date, two shake sheet samples were taken on the center two rows (10-row ft total) of all plots. Plant bug control was evaluated 28 Jul, 4 d after initial application (4 DAT1), 1 Aug (8 DAT1), 4 Aug (11 DAT1), and 11 Aug (4 DAT2). Yield was taken 9 Oct by harvesting the two center rows with a spindle picker modified to collect data for small plots. Total plant bug data 11 DAT1 and 4 DAT1 were log transformed (x + 1) prior to the ANOVA and an F-protected Least Significant Difference (LSD, P < 0.05) was used to distinguish treatment mean differences. Nontransformed means are presented in the tables.