Host-Free Survival of Boll Weevils (Coleoptera: Curculionidae) Previously Fed Vegetative-Stage Regrowth Cotton

Abstract

The need to minimize populations of overwintering boll weevils (Anthonomus grandis Boheman) in eradication programs is widely recognized, but the potential contribution of nonfruiting regrowth cotton (Gossypium hirsutum L.) to weevil survival has not been directly examined. We conducted experiments in 2002 and 2003 to examine the host-free survival of weevils previously supplied vegetative-stage regrowth cotton. Weevils, 1–3 d after eclosion, were caged with vegetative regrowth cotton under ambient environmental conditions (2002), or in a controlled environment (23.9 ± 2°C, 13:11 [L:D] h photoperiod, 2003). Four cohorts of each weevil sex were examined each year. Of the 60 weevils dissected in 2002, 12% possessed the hypertrophied fat bodies associated with diapause and extended host-free survival. In both years, the majority of weevils (>75%) died during the initial 3 wks of the host-free period. No differences in host-free survival were detected between weevil sexes, but differences were observed among replicates of the experiment established on different dates. Survival patterns among replicates, however, did not strictly follow a seasonal pattern. Overall, approximately 5% of the weevils survived ≥12 wks beyond the feeding period. Maximum observed host-free longevities were 21 wks in 2002 and 19 wks in 2003. Our findings suggest vegetative-stage regrowth cotton should not be disregarded in eradication zones, particularly in those experiencing unsatisfactory progress or resurgence of weevil populations.

Temperature Influences on Diapause Induction and Survival in the Boll Weevil (Coleoptera: Curculionidae)

“…The higher host-free survival rates of males compared with females are difficult to interpret unambiguously, especially considering that several previous studies using either vegetative stage cotton as food ( Esquivel et al 2004 , Suh and Spurgeon 2006 ) or observations of survival under ambient conditions ( Westbrook et al 2003 , Spurgeon 2008 ) did not report similar differences. Regardless, differences observed in this study occurred early in the host-free survival period.…”

Morphology, Diet, and Temperature-Dependent Host-Free Survival of the Boll Weevil, Anthonomus grandis (Coleoptera: Curculionidae)

“…Several studies have demonstrated extended host-free survival attributed to diet-induced diapause ( Suh and Spurgeon 2006 , Spurgeon et al 2008 , Spurgeon and Suh 2017 ). In addition, the duration of the induction period during which the weevils feed (D.W.S., unpublished data) and the temperature during this feeding period ( Spurgeon and Suh 2017 ) have been shown to influence subsequent survival.…”

“…One carton each of males and females, both fed the same diet, were combined in each of 14 survival cages. Cages were held in environmental chambers at 23.9 ± 1°C with a photoperiod of 13:11 (L:D) h. This temperature was selected based on results of Spurgeon et al (2008) and Suh and Spurgeon (2006) , because it produces mortality at a sufficiently low rate to distinguish relevant differences among treatments without unnecessarily prolonging the duration of the experiment. Each cage was inspected at 7-d intervals to remove dead weevils.…”

“… Showler (2009a) also provided a limited critique of the boll weevil diapause literature. For example, Suh and Spurgeon (2006) demonstrated extended survival of boll weevils feeding on vegetative-stage regrowth cotton. Showler (2009a) criticized their work, describing the plants as ‘actively fruiting’.…”

“… Showler (2009a) criticized their work, describing the plants as ‘actively fruiting’. However, the occurrence of squares (≤3 mm diameter) in their studies was limited to plants provided to only one of the 16 experimental cohorts of weevils ( Suh and Spurgeon 2006 ). Esquivel et al (2004) reported extended longevity of overwintered weevils provided vegetative-stage cotton.…”