Oystershell scale does not look like a typical insect, appearing instead as a small teardrop-shaped shell along the twigs and branches of trees. These adults do not have legs, eyes or antennae. They are attached to the plant by their mouthparts. The young, known as nymphs or crawlers, hatch out in May and walk along the branches until they locate a spot to feed and then become sessile as an adult. While the scale has been found on green ash, it has a large host range and can be found on lilacs, willows, poplars and maples.
Infestations usually begin on a single branch but can quickly expand to cover the entire tree.
Heavy infestations, where almost the entire branch or trunk is covered, can result in branch or tree mortality. Treatments are not effective at this time. May. W Mountain pine beetle is still flying in the Black Hills. The Forest Service will be conducting their annual aerial survey of the Hills to evaluate the threat and we will provide their predictions for next year in a later Pest Alert. The preliminary results from our pesticide trials, performed in cooperation with the Forest Service, indicate that Sevin XLR and Astro are equally, and highly, effective at preventing successful colonization by the mountain pine beetles.