Physiological development and dispersal ability of newly emerged Monochamus galloprovincialis

Abstract

Novel associations between exotic pathogens and native insects may result in major ecological and economical losses. In Europe, Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae) is the only known vector of the exotic pine wood nematode Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle (Nematoda: Aphelenchoididae), the causal agent of pine wilt disease (PWD). Transportation of goods containing nematode-infested beetles is the main pathway for the spread of the disease. In this scenario, management actions involving early detection and eradication are critical to stop further spread by the vector. Although dispersal of mature M. galloprovincialis has been successfully tracked using commercial baits and traps, dispersal ability of immature individuals is poorly understood. Sexual maturation and other physiological traits related to dispersal were studied for newly emerged M. galloprovincialis after different shoot-feeding spans. Sexual maturation was complete after on average 12 (males) or 13 (females) feeding days. Monochamus galloprovincialis adults emerged with an average of 10% lipid and 23.8% (males) or 29.9% (females) pterothorax muscle content, and these percentages did not change significantly during shoot feeding. Microtomography images of wing muscle structures at different maturation stages confirmed these results. Emerged adults that were kept unfed survived an average of 12 days in the lab. The ability of unfed immature insects to fly through hostless terrain was studied by marking and releasing newly emerged insects from a crop area located up to 3 km away from two small pine stands. The longest flown distance recorded was 2 km. Fitted regressions indicated that immature insects could have travelled up to 3 109 m to reach the experimental stands. We found that M. galloprovincialis emerge with welldeveloped thoracic muscles and energy reserves that enable them to sustain long flights over nonforested areas. These findings should aid managers and policy makers in devising sound procedures in areas where the risk of introducing PWD is high.

Monochamus species from different continents can be effectively detected with the same trapping protocol

“…Rassati et al (2012) reported that funnel traps baited with the same components of Galloprotect Pack are effective at low densities of Monochamus and can therefore be used as a general tool for beetle surveillance at ports of entry and forests, but also recommend that tree health assessments and trapping should be conducted outside of port areas as well (Rassati et al 2014). A constraint of this trap/lure combination is that newly emerged Monochamus adults require a sexual maturation feeding period, during which they are not attracted to the pheromones, kairomones, or host volatiles included in the Galloprotect Pack (Álvarez et al 2016), and during which they are able to disperse at least 2 km from the point of emergence (Sanchez-Husillos et al 2016). Identification and isolation of volatiles attractive to immature Monochamus adults should be a focus for the development of a truly comprehensive lure.…”