ABSTRACT

Maintaining profitability is key in any cropping system, causing producers to constantly strive to fine-tune management strategies to minimize inputs while optimizing yield. Because pesticides comprise a large portion of production inputs, reducing or enhancing their efficacy presents an avenue to increase profit. Pesticides containing both insecticidal and growth enhancing properties may be a viable option to increased profitability. In cotton (Gossypium hirsutum L.), early season applications of some insecticides have shown effects similar to those of plant growth regulators (PGRs). TRIMAX™ (imidacloprid) is one of these purported PGR insecticides. Centric^® 40WG (thiamethoxam) a product similar to TRIMAX™, may also have like properties due to the fact that they are both in the nitroguanidine class of insecticides.

A field study was conducted at the Texas A&M Agricultural Experiment Station in Burleson County, Texas to assess the physiological effects of Centric^® 40WG and TRIMAX™ on early season plant growth, rate of photosynthesis, yield and fiber quality. The statistical design consisted of a randomized complete block design with four replications. Treatments consisted of each of the insecticides being applied one, two, and three times at the 5-leaf stage, 5-leaf stage plus 10 days after initial treatment (DAIT), and 5-leaf stage plus 10 DAIT plus 20 DAIT. Rates consisted of TRIMAX™ and Centric^® 40WG being applied at 1.5 and 1.33 oz/A, respectively. All possible combinations, including the untreated control, were applied for a total of seven treatments. Data was collected for plant height, total number of nodes, biomass partitioning, photosynthetic rate, mid-season plant mapping, end of season box-mapping, and yield and fiber quality analysis.

No significant differences in lint yield were observed between the treatments. The three treatments of Centric® 40WG all showed a numerical increase in yield over the untreated control. One application of TRIMAX™ was numerically greater in yield than the untreated control, whereas two and three applications were slightly lower than the untreated control. Height, node, and biomass partitioning data showed no significant differences at any time these measurements were made during the growing season. Due to the wide variation in the photosynthesis readings, no conclusive results were obtained. Additional studies to this one-year study are necessary to evaluate the physiological responses of TRIMAX™ and Centric^® 40WG in cotton.