Canadian Forest Service Publications

Predicting Sirex noctilio and S. nigricornis emergence using degree days. 2013. Haavik, L.J.; Meeker, J.R.; Johnson,W.; Ryan, K.; Turgeon,J.J.; Allison, J.D. Entomologia Experimentalis et Applicata 149:177-184.

Year: 2013

Issued by: Great Lakes Forestry Centre

Catalog ID: 35156

Language: English

CFS Availability: PDF (request by e-mail)

Mark record


The study of temporal interactions between native insects and alien invaders can be facilitated by the ability to forecast adult emergence. We used field-collected adult emergence data of Sirex noctilio Fabricius (Hymenoptera: Siricidae), a woodwasp native of Eurasia that has recently invaded north eastern North America, and Sirex nigricornis Fabricius, a woodwasp native to North America, to develop and test cumulative degree-day (CDD) models. Five data sets were collected each in Ontario, Canada (S. noctilio) and Louisiana, USA (S. nigricornis) over 4 years; three data sets were used to develop models and two were used to test them. Males and females of each species were modelled separately. After testing several potential temperatures, chosen thresholds for CDD were 0°C lower threshold and 25°C upper threshold for both Sirex spp. We used a three-parameter Gompertz growth function to model Sirex spp. emergence against CDD. Models predicted 10% emergence of S. noctilio in Ontario after 1 239 and 1 280 CDD, for males (start date = 1 April; R2=0.91) and females (start date = April; R2 = 0.86), respectively. Models predicted 10% emergence of S. nigricornis in Louisiana after 3 980 and 5 016 CDD, for males (start date = 1 May; R2 - 0.83) and females (start date = 1 March; R2 = 0.73), respectively. Cumulative degree-day models predicted 10 and 90% emergence of woodwasp populations with less error (1-13%) than they did 50% emergence (5-27%). For both Sirex spp., male emergence began a few days before and concluded at about the same time as that of females. In southern Ontario, models predict that S. noctilio adults will be in flight between 1 015 and 2 430 CDD (1 April start date for CDD; from early-July until mid-September). In Louisiana, models predict that S. nigricornis adults will be in flight between 3 854 and 4 700 CDD (1May start date for CDD; from early-October until late-November.

Plain Language Summary

This manuscript describes work done to develop and test cumulative degree-day models to predict the emergence of the invasive woodwasp Sirex noctilio in Ontario and the native woodwasp Sirex nigricornis in Louisiana. Field-collected emergence data for both species were collected over several years, some of which were used to develop the models and the remaining to test them. Models with an acceptable error were successfully developed to predict emergence and the timing of adult flight of both species. Degree-day models for both Sirex species can be used to direct the seasonal timing of research that requires study or capture of adult wasps, and may be useful for S. noctilio management in North America (e.g., silvicultural treatments, release of natural enemies) that require knowledge of phenology in relation to heat unit accumulation.