PLANTÐINSECT INTERACTIONS Influence of Different Cotton Fruit Sizes on Boll Weevil (Coleoptera: Curculionidae) Oviposition and Survival to Adulthood

Understanding the critical host plant factors that determine oviposition behavior and survival of boll weevil, Anthonomus grandis grandis Boheman, on cotton, Gossypium hirsutum L., is important for developing successful pest management strategies. However, published information is both conßicting and limited regarding how different cotton fruit sizes affect boll weevil oviposition choices and subsequent larval survival to adulthood. Consequently, we used a standard based on fruit size diameter to evaluate boll weevil feeding and oviposition punctures, and survival to adulthood on 10 different cotton fruit sizes: squares of diameter 1.5Ð2.0 (pinhead), 3.0Ð3.5 (matchhead), 5Ð6, 7Ð8, or 9Ð10 mm; candle; and bolls of diameter 10Ð15, 15Ð20, 20Ð30, or 30 mm. Oviposition and feeding punctureswere signiÞcantly affected by cotton fruit size. Females did not oviposit in pinhead squares. The fewest eggs were oviposited in boll sizes 30 mm. The highest number of eggs was recorded in square sizes of 5Ð6 and 7Ð8 mm. Boll weevil survival to adulthood was highest on square sizes of 7Ð8 or 9Ð10 mm (58.6Ð59.7%). No survival occurred in matchhead squares or bolls 30 mm. Duration of development was longest on boll sizes of 15Ð20 and 20Ð30 mm (18.2Ð18.8 d). The growth index (percentage immature survival divided by immature developmental time) of female boll weevils was 2.8-fold higher in 7Ð8or 9Ð10-mmdiameter squares than in 20Ð30-mmdiameter bolls. This studywill improve our capacity to developmethods to predict fruit losses and changes in boll weevil populations in the Þeld, given a starting density of fruit suitable for oviposition, and a corresponding initial population density of weevils.