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

Abstract

The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), has been the most important pest of cotton (Gossypium spp.) wherever it occurs. Although eradication programs in the United States have reduced the range of this pest, the weevil remains an intractable problem in subtropical Texas, Mexico, and much of South America. A key to managing the weevil in the subtropics and tropics might lie in better understanding its diapause and overwintering survival in regions characterized by relatively high late-season temperatures. We examined the temporal patterns of acquisition of diapause characters at 18.3, 23.9, and 29.4°C, and the effects of temperature during the diapause-induction period on subsequent host-free survival at 23.9°C. Occurrence of the diapause characters generally increased with weevil age at all temperatures but appeared more rapidly at higher temperatures. Acquisition of the diapause characters tended to occur slightly earlier in female weevils compared with the male weevils. Despite the slower development of diapause characters at lower temperatures, when adult weevils were fed under low temperatures, subsequent host-free survival was enhanced. These results are consistent with reports of increased weevil survival with delayed entry into overwintering. Our findings also suggest that the potential host-free survival facilitated by diapause occurring in subtropical or tropical production regions may be reduced compared with dormancy developing in southern temperate regions. This reduced survival potential emphasizes the importance of a maximized host-free season and suggests that the late-season diapause spray intervals should be short enough to ensure that the number of dormant weevils developing in late-season cotton is minimized.

Diapause Response of the Boll Weevil (Coleoptera: Curculionidae) to Feeding Period Duration and Cotton Square Size

“…Spurgeon and Suh (2017) obtained similar results when boll weevils were fed under different temperatures. In their studies, temperatures during the feeding period influenced subsequent survival but at least some weevils were long-lived in response to each feeding period temperature.…”

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. Summy et al (1993) reported overwintering survival of the boll weevil was highest for weevils fed bolls compared with those fed squares.…”

“…During the 14-d feeding period preceding diapause or survival assessment, adult weevils in both experiments were held at 29.4 ± 1°C with a 13:11 (L:D) h photoperiod. Although feeding period duration influences host-free survival ( Spurgeon 2008 ; D.W.S., unpublished data), the 14-d period at temperatures ranging from 18.3 to 29.4°C has been shown to produce a high incidence of diapause and subsequent host-free survival ( Spurgeon and Suh 2017 ). A putative diapause-suppressing photoperiod was used because the daylength in South Texas during the late-season, when diapause would be induced, is longer than 12 h.…”

“…At the end of the feeding period, cartons were randomly assigned to survival temperatures (29.4°C, n = 6; 23.9°C, n = 8; 18.3°C, n = 6; 12.8°C, n = 8). These temperatures were selected for consistency with those used by Spurgeon and Suh (2017) , with the addition of a lower temperature (12.8°C) that would be typical of daytime highs during much of the noncotton season in the tropics and subtropics. Half of the cartons at each temperature contained males and half contained females.…”

“…In fairness, an association between these characters and an ecological consequence, such as extended survival, has not been established for the boll weevil. Our objectives were to 1) implement a range of diets to examine the relationship between the diapause criteria of Spurgeon et al (2003) and subsequent host-free survival and 2) employ a diet known to induce a high incidence of diapause ( Spurgeon and Suh 2017 ) to examine the influence of temperature on potential host-free survival.…”