Biology of the immature stages of the pecan weevil Curculio caryae (Horn) and oviposition habits of the adult weevil by Luis Alberto Aguirre Uribe

Abstract

The biology of the immature stages and oviposition habits of the adult pecan weevil were studied under laboratory conditions at College Station, Texas. Pecan weevil development occurs most rapidly at 25??C among the 4 temperatures tested, taking 7 to 8 days for eggs; 1st and 2nd instars, 3 days each; 3rd instar, 4 to 6 days; and 4th instar, 12 to 25 days (avg. 18.3 days). Developmental time from oviposition to larval emergence averaged 33.3 days. Developmental times at 28??C are as follows: Egg, 8 to 9 days; 1st instar, 5 days; 2nd instar, 4 days; and 3 instar, 5 days. Although 4th instar was found the 19th. day after oviposition, no oviposition occurred on the pecans that were left undisturbed for emergence, leaving this part of development unanswered. Temperatures of 19?? and 22??C were found to be adverse for pecan weevil development. Larval weight gain was found to be directly related to larval age. Post-emergence longevity of early emerged adult weevils was 15.46 and 13.92 days for females and males respectively; and 10.93 and 9.10 days for those emerging late. No statistical difference in longevity was found between sexes; however, a statistical difference was found between early and late emerged weevils with those emerging early living longer than those emerging late. More early emerged females oviposited (70%), when compared with those that emerged late (40%), indicating that less damage might be expected when a late emerging population occurs in the field. Fecundity is also affected by the time of emergence. Averages of 32.88 and 19 eggs/female were found for early and late emerged females respectively. Peak of oviposition occurred 5 days after emergence, with the range of most egg production being from 4 to 9 days. No difference was found in the average number of oviposition punctures per female between early (9.47) and late (8.08) emerged weevils; however, early emerged females laid more eggs per puncture (3.45), than females that emerged late in the season (2.31)..