Weevils are beetles (order Coleoptera) in a superfamily (Cuculionoidea) of beetles with long snouts that host chewing mouthparts. These species tend to be quite small – less than a quarter inch in length, and they notable as economically significant insect pests. In North Carolina, Conotrachelus nenuphar is most commonly seen in April and May, with additional sightings common in July.
At least two weevil species affecting tree species in North Carolina have economic effects. The first is the Plum Curculio (Conotrachelus nenuphar), which damages fruit trees in the Rosaceae family. You can identify fruit damaged by the Plum Curculio by the small mushroom shaped scar it leaves behind when it lays its eggs. The Plum Curculio adults feed on the fruit and lay eggs inside of it in spring. As the larvae feed, they cause the fruit to drop early from the trees, destroying the crops. The larvae exist after a few weeks and pupate in the soil, starting the cycle anew. In North Carolina, Conotrachelus nenuphar is most commonly seen in April and May, with additional sightings common in July. To identify the Plum Curculio, look for a small, brown mottled weevil with humps and ridges on its wing covers (i.e., elytra).
The other weevil that affects tree species in North Carolina is the Acorn Weevil (Curculio glandinum). In fact, Weevils are thought to decrease oak regeneration in the hardwood forests of eastern North America. Like Plum Curculios, Acorn Weevils do the most damage when female bore holes into the acorn with their rostrum and proceed to lay eggs into the kernel or the part of the acorn containing the fatty seed leaves. The larvae or grubs feed on the kernel until the acorn drops to the ground. Then the grubs leave the acorn, and burrow into the ground, where they will pupate. Some researchers suspect that low temperatures might limit the northern distribution of Acorn Weevils, but they are found at least as far north as Ontario where they affect Red Oaks and Bur Oaks. Moreover, researchers have investigated weather light burns or thinning might change weevil abundance, but the effects of these management activities did not have a statistically significant effect on weevil population. Many species of weevils that affects southeastern forest trees exist, but they tend to have similar appearances as larvae. Curculio species tend to be most commonly seen in late September and early October. The Acorn Weevil is predominantly tan, mottled with brown, with a dark brown, curved rostrum.
References
Lombardo, J. A., and B. C. McCarthy. 2008. Forest management and Curculionid weevil diversity in mixed oak forests of Southeastern Ohio. Natural Areas Journal 28: 363-369.
Udaka, H. and B. J. Sinclair. (2014). The overwintering biology of the acorn weevil, Curculio glandium in southwestern Ontario. Journal of Thermal Biology, 44 (2014): 103-109. https://doi.org/10.1016/j.jtherbio.2014.02.019.
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