Boll Removal Studies Provide Insights into Compensation Ability of Virginia Cotton: A Necessary Step for Further Improvement of Insect Management Strategies

In developing management strategies for hemipteran pests in cotton (Gossypium hirsutum L.), it is important to understand the potential of plants to compensate for loss of the fruiting structures. Because of its northern latitude, Virginia has fewer available heat units relative to other cotton-producing states. Therefore, there may be limited opportunity for compensation relative to more southerly production areas. Previous work in Virginia demonstrated that cotton can sustain relatively high levels of first position square loss with no yield loss. This study evaluated the impact of a single event loss of 10–14-d-old bolls via mechanical removal on cotton lint yields with the premise that boll loss would have greater impact than square loss as less time and fewer heat units are available for compensation. Field experiments examining four levels of boll removal (0, 5,15 and 20%) were conducted in 2001,2002 and 2003. Each boll removal level was imposed at three different dates, beginning 2 wks after first flower and at 3- to 5-d intervals thereafter. Yields ranged from 1103–1422 in 2001, 909–1124 in 2002, and 843–1015 kg lint per ha in 2003. There were no significant differences in lint yields among the boll removal dates or removal levels. The results of our study showed that cotton in Virginia, which approaches the northernmost latitude for cotton production, is capable of sustaining losses as high as 20% of 10–14-d-old bolls at a single removal event without affecting lint yield. Results were consistent despite the wide variation in rainfall and temperatures during the 3 study years.