Effect of insecticide termination at varying heat units after cutout on yield, boll weight, fiber quality and carbon movement

摘要

COTMAN, a crop monitoring program for cotton, uses the concept of 350 heat units after anthesis of the last flower population at five nodes above white flower (NAWF=5) for termination of insecticide applications. It is hypothesized that terminatinginsecticide use at 350 heat units after NAWF=5 results in a higher yield than when terminating at either lower or higher heat unit values, although evidence is lacking. To test this hypothesis, a field study was conducted at Clarkedale to determine how removing unwanted fruit above NAWF=5 at different heat units impacted carbon movement, lint yield and boll weight and quality of first position bolls at NAWF=5. Treatments consisted of a control with no fruit removal, and hand removal of all upper-canopyfruit above NAWF=5 at 250,350 and 450 heat units. Field experiments conducted from 1998 to 2000 have not shown a clear yield trend between treatments, however boll weight was usually increased the most when fruit was removed at NAWF=5 +350 heat units. Results from 2000 indicated that boll weight of first position bolls at NAWF=5 were numericallyincreased when fruit was removed at NAWF=5 + 350 heat units, however yield and fiber quality were numerically reduced. Favorable late-season weather patterns in2000, which extended the cotton growing season and filled upper bolls that normally fail to reach maturity, may be the reason for higher yields observedby the control. Due to these abnormal late-season weather patterns the past few years, additional field studies are needed to determine if removing fruit at NAWF=5 + 350 heat units provides a yield advantage.