|Affected arborvitae (Thuja sp.) along the road.|
When I first saw the section I observed a few large holes - about 1/4 inch in diameter - in the top with sawdust being pushed from them. This was clearly a boring insect, but was it a metallic wood borer (Buprestidae), longhorn beetle (Cerambycidae), or something else? Turns out, after prying some of the bark back, there were several large (up to 3/4 inch), legless larvae boring just under the surface. The larvae were very clearly weevils (Curculionidae), but what species?
|Weevil larvae preserved for future study.|
Because larval weevils are nearly impossible to identify, it was my goal to rear the larvae until they emerged as adults so I could then identify them. I waited...and waited...and waited. Some beetles (under the right conditions) can exist as larvae in wood for decades and even up to 50 (!) years - I wasn't going to wait that long. Fortunately, after removing a little more bark some weeks later I found pupae. Finally, adults in progress! A week or so later and I had adults which I identified as the cypress weevil (Eudociminus mannerheimii (Boheman)).
|Cypress weevil (Eudociminus mannerheimii) showing life stages and damage.|
This fairly large weevil (10-17 mm) is known from a few hosts, especially baldcypress (Taxodium distichum), but also Japanese cedar (Cryptomeria japonica), Leyland cypress (Cupressocyparis leylandii), and arborvitae (Thuja sp.). It's biology appears to be similar to the related pine regeneration weevils, Hylobius pales (Herbst) and Pachylobius picivorus (Germar). The beetles lay eggs on weakened or dying trees and the larvae burrow beneath the bark before creating a deeper hole to pupate in. Adults appear to emerge in the Spring and will feed on the bark of small, green branches. Because they generally attack already-declining trees they are not always the main issue. However, this sample had so many weevils in one small section that I believe they were a major factor causing health issues for the trees. Follow the links below to read more about this weevil and learn about management practices. In the mean time I am going to smoke my proverbial cigar and curate these specimens to go into the NCSU Insect Museum which only had four total specimens!
NCSU Entomology Insect Note on Eudociminus mannerheimii
UF Featured Creatures on Eudociminus mannerheimii