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Insecticidal Effects on Fruiting and Yield Enhancement in Cotton

Brett M. Niccum, J.T. Cothren, Josh Bynum, and Tony Provin

ABSTRACT

Past research in cotton (Gossypium hirsutum L.) has indicated that some pesticides, including insecticides, may contain plant growth regulator (PGR) properties (Lincoln and Dean, 1976; Cothren et al., 1984; Bauer and Cothren, 1990). TRIMAX™, an imidacloprid, an insecticide produced by the Bayer Corporation and Centric® 40WG, a thiamethoxam, an insecticide produced by 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 was conducted under irrigated conditions to observe the physiological effects of foliar treatments of TRIMAX™ and Centric® 40WG on early season plant growth, chlorophyll content, yield, and fiber quality. A secondary objective of the study was to determine the correlations between data derived from a Minolta SPAD meter, total nitrogen content, and chlorophyll content of cotton. The experimental design consisted of four replications within a randomized complete block (RCB). Treatments consisted of one, two, and three applications of TRIMAX™, one, two, and three applications of Centric® 40WG, and a control, totaling seven treatments within the RCB. TRIMAX™ 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® 40WG, applied at a labeled rate of 1.33 oz/A, were made at the same timings as for TRIMAX™. 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™ and the three treatment of Centric® 40WG all showed numerical increases in lint yield over the untreated control, however no significant differences were observed. Three applications of TRIMAX™ showed the greatest numerical increase in lint yield followed by one and two applications of TRIMAX™ then one, three, and two applications of Centric® 40WG. Percent nitrogen and SPAD values were highly correlated at P < .001. A simple linear regression model 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 did increase from one application to the next but no significant differences were found. Also height, node, and biomass partitioning data showed no significant differences at any time during the growing season. To evaluate the physiological responses to foliar treatments of TRIMAX™ and Centric® 40WG additional studies will be necessary.





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Document last modified 04/27/04