INSECTICIDAL EFFECTS ON FRUITING AND YIELD ENHANCEMENT IN COTTON

摘要

Past research in cotton (Gossypium hirsutum L.) has indicated that some pesticides, including insecticides, may contain plantgrowth regulator (PGR) properties (Lincoln and Dean, 1976; Cothren et al., 1984; Bauer and Cothren, 1990). TRIMAX~(TM),an imidacloprid, an insecticide produced by the Bayer Corporation and Centric~R 40WG, a thiamethoxam, an insecticide producedby Syngenta, may both have similar insecticide and PGR qualities associated with them.A field study was conducted at the Texas A&M Agricultural Experiment Station in Burleson County, Texas. The study wasconducted under irrigated conditions to observe the physiological effects of foliar treatments of TRIMAX~(TM) and Centric~R40WG on early season plant growth, chlorophyll content, yield, and fiber quality. A secondary objective of the study was todetermine the correlations between data derived from a Minolta SPAD meter, total nitrogen content, and chlorophyll contentof cotton. The experimental design consisted of four replications within a randomized complete block (RCB). Treatmentsconsisted of one, two, and three applications of TRIMAX~(M), one, two, and three applications of Centric~R 40WG, and a control,totaling seven treatments within the RCB. TRIMAX~(TM) was applied at a labeled rate of 1.5 oz/A for each treatment.Timings of these applications occurred at the 10-leaf stage, 10-leaf stage plus 10 days after initial treatment (DAIT), and 10-leaf stage plus 10 DAIT plus 20 DAIT. Like applications of Centric~R 40WG, applied at a labeled rate of 1.33 oz/A, weremade at the same timings as for TRIMAX~(TM). Data was observed and recorded for plant height, total nodes, SPAD readings(as a reference for chlorophyll content), chlorophyll analysis, nitrogen analysis, biomass partitioning, mid-season plant mapping,end of season box mapping, and yield and fiber quality analysis.The three treatment of TRIMAX~(TM) and the three treatment of Centric~R 40WG all showed numerical increases in lint yieldover the untreated control, however no significant differences were observed. Three applications of TRIMAX~(TM) showed thegreatest numerical increase in lint yield followed by one and two applications of TRIMAX~(TM) then one, three, and two applicationsof Centric~R 40WG. Percent nitrogen and SPAD values were highly correlated at P < .001. A simple linear regressionmodel was chosen for the correlation between SPAD values and nitrogen content: % N = 12.564 – (0.182 x SPAD).However, no correlation was found for chlorophyll levels in relation to nitrogen content or SPAD values. SPAD reading didincrease from one application to the next but no significant differences were found. Also height, node, and biomass partitioningdata showed no significant differences at any time during the growing season. To evaluate the physiological responses tofoliar treatments of TRIMAX~(TM) and Centric~R 40WG additional studies will be necessary.