Growth and Developmental Response of Cotton Cultivars to Different Levels of Lygus Infestation

Two cultivars, DP 104 B2RF (early season) and DP 161 B2RF (full season), were evaluated for their responses to Lygus-induced fruit loss and yield compensation capability. Pre-flower square loss treatment levels were achieved by augmenting natural plant bug populations with laboratory-reared nymphs. Nymphs were released weekly during the first three weeks of squaring. Insect release treatments included: 1) augmentation of 2-3 (low) bugs per plant, 2) augmentation of 4-6 (high) bugs per plant, 3) 0 bugs augmented (naturally occurring background density), and 4) 0 bugs as achieved through insecticide applications. The test was deployed in a 2 (cultivars) x 4 (insect release treatments) factorial arrangement with a randomized complete block design for three years. Both cultivars showed exceptional lint yield compensation for up to 20-26% and 40-54% early fruit loss during 2009 and 2010, respectively. In the bug-augmented plots, lower 2009 compensation percentages were observed because of lower percentages of early fruit losses (fewer bugs released). We were expecting a significant difference in fruit retention and compensation ability between these two cultivars in 2009, but those anticipated differences were not apparent, possibly due to an insufficient level of bug-inflicted fruit loss in these plants. In 2010 the early-terminating cultivar (DP 104 B2RF) compensated fully for both 40 and 48% pre-flower fruit loss, whereas the full-season cultivar (DP 161 B2RF) compensated for 52 and 54% fruit loss. In both cultivars, insect-induced early fruit loss appeared to cause fruit overcompensation. Upward shift and delayed cut-out, as is indicated by 2010 Squaremap data, resulted in compensation/overcompensation of 40-54% early fruit loss. Data for 2011 will also be added by the time this manuscript is written for the proceeding.