Impact of at-planting insecticides and transgenic technology on thrips populations in Mississippi cotton, 2023

On 4 May 2023, a trial was planted at the Delta Research and Extension Center in Stoneville, Mississippi, to determine the impacts of various at-planting insecticides and transgenic Bacillus thuringiensis (Bt) technology on thrips densities on cotton. Plot size was 4 rows wide (40-inch centers) by 40 feet in length. Treatments were implemented in an RCB with 4 replications. Data collected included thrips injury ratings, Canopeo measurements, adult thrips counts, and immature thrips counts at 14, 21, 28, and 32 days after planting (DAP) (1, 2, 3, and 4 true leaf [TL] stages, respectively). Injury ratings were taken using a 0–5 scale with 0 being no damage and 5 being a dead plant. Canopeo ratings were taken using the Canopeo smartphone app (Mathworks, Inc., Natick, Massachusetts), which uses color values of an image to determine the green canopy cover. Thrips densities were determined by carefully taking 5 random plants from the center 2 rows of each plot and placing them in a quart-sized plastic sealable bag before being transported to the lab for processing. Once in the lab, plants were washed with an ethanol solution through a No. 10 (2 mm) brass-framed stainless mesh sieve into a No. 325 (45-µm) sieve and then onto filter paper. The filter paper was vacuum suctioned, and thrips were counted under a microscope. Immature and adult thrips were differentiated and recorded separately. Yield was collected using a mechanical picker and converted using a 40% gin turnout. Data were analyzed with ANOVA, and means were separated using Fisher’s Protected Least Significant Difference (P = 0.05).

All treatments, excluding Orthene 97 (IST), had significantly lower injury ratings compared to the untreated check at the 1 and 2 TL stages (Table 1). At the 3 and 4 TL stages, all treatments had significantly lower injury ratings compared to the untreated check. However, the Orthene 97 (IST) treatment injury rating was significantly higher than all other treatments. For Canopeo measurements, no significant differences were observed until the 4 TL stages (Table 2). At this stage, AgLogic (IF), Admire Pro (IST), ThryvOn (Bt), and ThryvOn (Bt) + Gaucho 600 (IST) had significantly higher Canopeo ratings than the untreated check. However, these same treatments were not different from Orthene 97 (IST), Orthene 97 (IST) + Gaucho 600 (IST), and Aeris. Adult thrips counts showed significantly lower adult densities in all treatments compared to the untreated check at the 1 TL stage (Table 3). At the 2 TL stages, only the ThryvOn (Bt) treatment had lower adult thrips densities than the untreated check. No significant differences were observed at the 3 or 4 TL stages. Immature thrips counts showed significantly lower immature thrips densities in all treatments compared to the untreated check at the 1 TL stage (Table 4). At the 2 TL stage, all treatments except for Orthene 97 (IST) had lower immature densities than the untreated check. At the 3 TL stage, only Orthene 97 (IST) + Gaucho 600 (IST), Gaucho 600 (IST), AgLogic (IF), Admire Pro (IF), ThryvOn (Bt), and ThryvOn (Bt) + Gaucho 600 (IST) had lower immature thrips densities than the untreated check. Orthene 97 (IST) and Aeris (IST) were not significantly different than the untreated check. No significant differences in lint yield were observed in the Deltapine 1845 BG3XF (non-ThryvOn) variety (Table 5). There was also no significant variation in lint yield between the 2 treatments with the ThryvOn variety.¹

Footnotes