ABSTRACT

Experiments were undertaken in three seasons (2001-2003) in Virginia cotton to evaluate the response to loss of 10 to 14-day old bolls via mechanical removal. Four levels of boll removal (0, 5, 15 and 20%) were imposed on three dates beginning 14 days after first flower and repeated two times, each five days after the last. Results showed no significant differences in lint yields among the boll removal levels or removal dates, in either 2002 or 2003 studies. In 2001, there was a statistically significant reduction at the 20 percent removal rate at the second removal date. The same trend occurred at the third removal date; however, the difference was not significant. In addition, in an effort to document the severity of bug species (stink bugs and plant bugs), a 2-year survey was conducted of 40 randomly selected grower fields for presence of bug species and plant damage. Field surveys showed that plant bug, Lygus lineolaris, was the predominant pest during the weeks between square formation and early boll development. Plant bug populations and levels of damage to bolls were considerably higher in 2003 compared with 2002. Plant bug was present in 80 and 95% of the fields in 2002 and 2003, respectively. In 2002, only 7 percent of the fields surveyed reached or exceeded the 10 percent boll damage threshold compared with 30 percent in 2003. Results showed that although not strongly related (R² = 0.4437), retention rate (percent) decreased as number of plant bugs increased (Y = -0.8504x + 80.678). Sweep net, shake cloth, and dirty bloom samples were variable and did not relate well to levels of boll damage. Percent square retention and boll damage assessments seem to be the best indicators of the need to spray, with the other information, i.e., insects and dirty blooms are present, serving to alert scouts of the need to do more intensive square or boll sampling.