Mn. Parajulee et al., CLIMATIC DATA-BASED ANALYSIS OF BOLL-WEEVIL (COLEOPTERA, CURCULIONIDAE) OVERWINTERING SURVIVAL AND SPRING EMERGENCE, Environmental entomology, 25(5), 1996, pp. 882-894
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.