|HOLLINGSWORTH, ROBERT - Retired ARS Employee|
|SABADO-HALPERN, MEHANA - University Of Hawaii|
|JOHNSON, MELISSA - Oak Ridge Institute For Science And Education (ORISE)|
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2019
Publication Date: 7/17/2019
Citation: Hamilton, L.J., Hollingsworth, R.G., Sabado-Halpern, M., Manoukis, N., Follett, P.A., Johnson, M. 2019. Coffee berry borer (Hypothenemus hampei) (Coleoptera: Curculionidae) development across an elevational gradient on Hawai‘i Island: applying laboratory degree-day predictions to natural field populations. PLoS One. 14(7). https://doi.org/10.1371/journal.pone.0218321.
Interpretive Summary: Coffee berry borer is the most devastating insect pest of coffee throughout the world. One of the major difficulties in managing this pest in Hawaii is that the land area suitable for coffee agriculture is extremely variable over short distances. The extreme variability in climate and topography across Hawaii’s coffee-growing regions necessitates a landscape-level approach to improving IPM. In the present study, we collected weather data at both macro- (farm-level) and micro-scales (branch-level) from commercial coffee farms spanning an elevational gradient of 600 m on Hawai‘i Island, and employed a novel technique using alcohol lures to initiate infestation of coffee berries in the field by naturally-occurring adult females. We followed CBB development in the field from the time of infestation by founding females through to the development of mature F1 adults. Our objective was to compare development rates observed in the field with those predicted from previous studies under constant conditions, in order to assess the fit of degree-day models based on those laboratory data to the heterogeneous environmental conditions that characterize Hawaii’s coffee-growing regions.
Technical Abstract: Coffee berry borer (CBB, Hypothenemus hampei) (Coleoptera: Curculionidae: Scolytinae) is the most destructive pest of coffee worldwide. Information on CBB development times can be used to predict the initiation of new infestation cycles early in the coffee-growing season and thus inform the timing of insecticide applications. While laboratory estimates of CBB development under constant conditions exist, they have not been applied under the heterogeneous environmental conditions that characterize many coffee-growing regions. We measured CBB development times and abundance in commercial coffee farms across an elevational gradient on Hawai‘i Island and applied thermal accumulation models from previous laboratory studies to test their fit to field data. Artificial lures were used to infest coffee berries at five farms ranging in elevation from 279-792 m, and weather variables were monitored at macro (farm-level) and micro (branch-level) scales. CBB development was followed in the field from the time of initial berry infestation by the founding female through the development of F1 mature adults. Mean development time from egg to adult across all sites was 38.5 ± 3.46 days, while the mean time required for the completion of a full life cycle (from time of infestation to presence of mature F1 females) was 50.9 ± 3.35 days. Development time increased with increasing elevation and decreasing temperature. Using macro-scale temperature data and two different estimates for the lower temperature threshold (14.9°C and 13.9°C), we estimated a mean requirement of 332 ± 14 degree-days and 386 ± 16 degree-days, respectively, from the time of berry infestation to the initiation of a new reproductive cycle in mature coffee berries. Similar estimates were obtained using micro-scale temperature data, indicating that macro-scale temperature monitoring is sufficient for life-cycle prediction. We also present a model relating elevation to number of CBB generations per month. Our findings suggest that CBB development times from laboratory studies are generally applicable to field conditions on Hawai‘i Island and can be used as a decision support tool to improve IPM strategies for this worldwide pest of coffee.