D3208: Forest management during drought events: an effective control method for Sirex nigricornis, a proxy for Sirex noctilio

The European Woodwasp (Sirex noctilio Fabricius) was detected in North America in 2004. Thus far in North America, S. noctilio has not caused major tree mortality, despite its ability to cause >70% mortality in poorly managed stands throughout the Southern Hemisphere. Forest stand thinning significantly reduces S. noctilio related mortality, except for during significant drought years. Although not currently classified as invasive in North America, S. noctilio exhibits eruptive population dynamics. These populations often remain at low population levels for up to 12 years before reaching outbreak populations, therefore it should not yet be disregarded as a significant forest pest in North America. The objectives of this study are to determine how drought conditions and basal area interact to influence native woodwasp abundance and to develop forest management recommendations to minimize the outbreak potential of their conger Sirex noctilio. A cross-hatched log stack and Lindgren funnel trap were used to sample siricid populations. Treatments included thinned and unthinned pine plantations in drought and non-drought stressed areas in Mississippi, North Carolina, and Ontario, Canada. We found that drought-stressed areas presented higher woodwasp capture, but that basal area had no effect. These results may advise forest management as Sirex noctilio increases its range to the southeastern US.