Predicting Sirex noctilio and S. nigricornis emergence using degree days

Abstract

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 northeastern 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; R 2 = 0.91) and females (start date = 1 April; R 2 = 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; R 2 = 0.83) and females (start date = 1 March; R 2 = 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 (1 May start date for CDD; from early-October until late-November).

Effects of Forest Type and Management on Native Wood Wasp Abundance (Hymenoptera: Siricidae) in Mississippi, United States

“…Emergence began in early Oct and ceased in mid-to late Dec, which agrees with other reports of Sirex emergence in the Southeast (Haavik et al 2013). A test of parallelism found significant differences among years (F = 48.621; df = 8; P < 0.0001), and a final model ( Fig.…”

“…However, if this trend of higher winter temperatures continued over several years, we might expect to see earlier emergence of natives if they follow the same early patterns as S. noctilio does in consistently warmer temperatures. Zylstra et al (2010) showed that 79% of captured S. noctilio were collected in New York, USA, by the beginning of Aug and all S. noctilio had been captured by the end of Sep. Haavik et al (2013) found S. noctilio emerging from Jul through Sep in Ontario, Canada, and their findings are consistent with additional studies (e.g., Myers et al 2014), which predict future S. noctilio emergence in the Southeast occurring as early as mid-Apr. These patterns indicate that S. nigricornis and S. noctilio will not overlap in seasonal flight patterns, even in the warmer climate of the Southeast.…”

Comparing functional traits and abundance of invasive versus native woodwasps

“…Sirex noctilio has a temporal advantage over S. nigricornis as many emerge 1-2 months before S. nigricornis, although there is overlap in emergence between these species in northeastern North America (Ryan et al 2012a;Haavik et al 2013;Hartshorn et al 2016;Suppl. material 1: B).…”

Development of insects under fluctuating temperature: a review and case study

“…; Haavik et al. ; Sridhar and Reddy ). A variety of abiotic factors, such as temperature, humidity and photoperiod, and biotic factors influence developmental rate (Uvarov ; Krasnov et al.…”

“…; Haavik et al. ), its simplifying assumptions are routinely neglected (but see Amendt ). For example, because DD measures the total amount of accumulated heat, how it is accumulated (e.g.…”