Canadian Forest Service Publications
Host tree species and burn treatment as determinants of preference and suitability for Monochamus scutellatus scutellatus (Coleoptera: Cerambycidae). 2013. Breton, Y.; Hébert, C.; Ibarzabal, J.; Berthiaume, R.; Bauce, É. Environ. Entomol. 42:270-276.
Issued by: Laurentian Forestry Centre
Catalog ID: 34666
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After fire, the whitespotted sawyer, Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae), is considered one of the most damaging xylophagous insects by forest industries in the eastern boreal forest of North America. Although this species is often considered opportunistic because it dwells on various stressed host trees, it can be found in very high abundance after forest fire and, consequently, it has been suspected of being a pyrophilous species or fire-associated species. The aim of this study was Þrst to determine whether the whitespotted sawyer lays eggs preferentially on burned rather than unburned hosts, and second, to determine its preference between black spruce (Picea mariana [Mill.] B.S.P.) and jack pine (Pinus banksiana Lamb.) for oviposition. Host suitability also was estimated to determine if whitespotted sawyer females make optimal choices to maximize offspring development. To determine host suitability, we used the abundance distribution of larval instars as a proxy of larval development quickness and we compared weight and head-capsule width of larvae of different larval instars as measures of insect growth in each type of log. Based on the frequency of oviposition behavior, females showed no preference for either burned or unburned black spruce logs, and both were equally suitable for larval development. Furthermore, females laid more eggs on black spruce than on jack pine, but host suitability was not statistically affected. Nevertheless, larvae had mostly reached the fourth instar on black spruce, whereas those on jack pine were mostly at the third instar, suggesting faster development on black spruce.
Plain Language Summary
The whitespotted sawyer is an insect that quickly invades burned forests in Canada. The galleries burrowed by its larvae damage the wood and reduce its market value.
In order to better understand the behaviour of the whitespotted sawyer, researchers have tested its preference between charred logs and healthy black spruce logs and between charred logs of black spruce and jack pine. They discovered that when laying its eggs, the female prefers black spruce over jack pine, but she makes no distinction between wood that is charred or not.
In light of this study, the presence of charred wood is therefore not a factor that can explain why whitespotted sawyers invade burned forests.