Field trails were conducted in Artesia and Las Cruces, New Mexico to determine if cotton can compensate for mid to late season looses of squares or bolls from bollworm in New Mexico. Damage was simulated by manually removing squares and small bolls using a locally adapted variety Acala 1517-99. Squares were removed in early-mid August, bolls in late August to early September. Yields were determined by node and position for 10 ft of row plots by removing whole plants from the field.

Highest yields were in undisturbed and earlier square removal plots. Untreated plots had 26 bolls/ft compared to 18-22 bolls/ft in the damaged plots. Yield compensation is suggested since some damaged plots had significantly larger bolls than the undamaged plots. Plots that had squares removed August 15 had bolls 12% larger than all other plots with 1.8 grams of lint /boll compared to 1.6 grams lint/boll in all other plots. This increase was due to an increase in lint per lock rather than an increased number of locks. The number of locks were similar across all plots. The amount of lint/lock was also significantly higher with 0.46 g/lock compared to 0.41-0.44 for all other treatments. On August 15 squares were removed from nodes 15-20. Plant mapping indicated 50% of plants had the last fruiting node on node 20 on that date.

Yield differences were not significant in the first year of testing using 10 ft plots. Recently, larger 30 ft. plots were used to evaluate yield differences after similar square and boll losses. Cotton was hand picked but not sorted according to node or position. Yield differences in those trials will be discussed.