CLIMATIC DATA-BASED ANALYSIS OF BOLL-WEEVIL (COLEOPTERA, CURCULIONIDAE) OVERWINTERING SURVIVAL AND SPRING EMERGENCE

Analysis of data from a 15-yr study; composed of 97 boll weevil cohort s from overwintering habitats in the Rolling Plains of Texas, showed t hat overwintering survivorship and spring/summer emergence were influe nced by the day of the year (DOY) when the weevils entered overwinteri ng habitat (DOYin), the amount of rainfall, and habitat temperatures e xperienced by the weevils during diapause. The earlier the date that w eevils entered overwintering habitat or the greater the amount of rain occurring before emergence of the 1st weevil, the greater the positiv e degree-days (>6.1 degrees C) required for weevils to emerge from ove rwintering habitat. There was no significant correlation between the t imings of weevil emergence and the winter severity, measured in terms of negative degree-days (<0.0 degrees C). Multiple least squares regre ssion analyses describing the positive degree-days required for the we evils to start emergence (DDstart) and the time required for all weevi ls to emerge (duration of emergence) (DDemerg) explained 88 and 77% of the variability in the data, respectively With independent data 75 an d 36% of the variability were explained for DDstart and DDemerg, respe ctively. Overwintering survival ranged from 0 to 50% in the 15-yr stud y. Survivorship was positively correlated with DOYin, and negatively c orrelated with NDDstart and DDstart. Multiple regression analysis with DOYin, negative degree-days, rainfall, positive degree-days, and thei r Ist order interactions explained 99% of the variability in overwinte ring survival. With independent data, 74% of the variability was expla ined by the survival function. A chi-square rest for goodness-of-fit s howed that 74% of the survival estimates did not differ significantly from their observed values. In contrast, when compared with independen t data, 37% of the survival estimates did not differ significantly fro m their observed values. The spring/summer emergence pattern for the o verwintering weevils was described by a sigmoid function that explaine d 95 and 92% of the variability for the verification data set and the independent data set, respectively. Boll weevil overwintering emergenc e patterns can be predicted with considerable accuracy, but greater kn owledge of factors affecting bell weevil overwintering survival and th e time to completion of emergence is required for these to be predicte d accurately.