Biological parameters of stem borer Stromatium barbatum reared on grapevine wood logs under laboratory conditions

Abstract

Stem borer Stromatium barbatum has recently emerged as a serious pest problem of grapevines in India. Hidden biology and lack of effective chemical control of stem borer warranted finding out weak links in its life cycle which aids in formulating effective management strategies. Being a monovoltine pest with annual life cycle, the systematic studies on developmental biology and stage specific mortality of stem borer in grapes are limited. In present study, a cohort life table was constructed for S. barbatum by rearing it on grapevine wood logs in the laboratory at 27 ± 1 ℃ temperature and 65 ± 5% RH. The life cycle of S. barbatum was tracked from egg hatching through larval and pupal stages till adult emergence and observations were recorded on stage specific developmental durations and mortality of immature stages, and longevity and fecundity of adult stages. The results revealed that the mean durations of egg, larvae and pupae were 6.60 ± 0.28 days, 296.10 ± 1.06 days and 19.70 ± 1.17 days, respectively. The adults after emerging from pupae could survive up to 36.40 ± 0.81 days. The egg hatching and adult emergence from pupae were 42.51% and 83.02%, respectively. S. barbatum population attained a net reproductive rate of 64.96 females/female/generation and a gross reproductive rate of 72.93 females/female/generation in her mean oviposition period of 9.80 ± 0.13 days. The data indicated that, S. barbatum population potentially might increase with an intrinsic rate (r_m) of 0.087 females/female/day and a finite rate $(\lambda )$ of 1.09 females/ female/ day with a doubling time of 9.98 days and a mean generation time of 324.30 days. The mortality was relatively higher during the egg and larval stages, which was then gradually decreased for rest of the life span when S. babatum was reared on grapevine wood logs under laboratory conditions. Generation mortality for S. barbatum was 90.72%. The present study has generated detailed information on critical life events such as days to egg hatch, adult longevity and fecundity, time required for adults to oviposit after mating, and age-stage specific mortality. This could facilitate formulation and implementation of effective management strategies for S. barbatum in grape vineyards.