Bracon mellitor Say (Hymenoptera: Braconidae) Diapause in the Texas Rolling Plains

Abstract

Populations of Bracon mellitor Say in the Texas Rolling Plains initiated diapause in cotton squares in early fall, with all of the population entering diapause by late October. High temperatures delayed fall diapause initiation, and photoperiod maintained and terminated diapause. A critical light cycle ranging from 10:10 to 11:05 terminated diapause for females, whereas diapause termination for males occurred at light cycles as short as 10:00 hours. For most individuals, diapause was terminated by 20 February. Spring emergence occurred from late March to mid-May but most individuals emerged between 4 and 26 April. Julian date accounted for more variability in cumulative percentage of emergence than cumulative degree-days. This suggests that the rate of postdiapause development may be dependent upon temperature and intrinsic or extrinsic factors not measured. Multiple regression equations, utilizing both Julian date and cumulative degree-days are presented which may be useful to predict spring emergence patterns.