Oystershell Scale (Lepidosaphes ulmi) is a type of armored scale insect that infests deciduous and evergreen trees, including elms, oaks, and maples. The scale insects have a hard, circular, gray or brown shell-like covering that protects their body and acts as a defense mechanism against predators and pesticides. Oystershell scale can significantly weaken a tree, making it vulnerable to other pests and diseases. The insect feeds on sap from the tree, causing yellowing or wilting of leaves, stunted growth, and twig or branch dieback.
The insects overwinter as adult females on the bark of the tree, and in the spring, they lay their eggs beneath the scale covering. The eggs hatch into crawler nymphs, which move around the tree until they find a suitable feeding spot, where they insert their needle-like mouthparts into the tree's sap-conducting vessels. From then on, the nymphs don't move again and feed on the tree's sap until they reach adulthood. The adult males emerge from the scale covering and mate with the adult females, and the cycle starts over again.
To manage an infestation of oystershell scale, it's essential to identify the problem early and take appropriate action. Cultural control measures, such as proper watering and fertilization, can help keep trees healthy and reduce stress, making them less susceptible to scale insect infestations. If the infestation is severe, chemical treatments such as horticultural oil or insecticide applications can be effective in controlling the scale insects.
In conclusion, oystershell scale is a significant pest of deciduous and evergreen trees, and prompt action is necessary to manage infestations and protect trees from damage and decline. Proper tree maintenance, including regular inspections and prompt treatment when necessary, is essential for keeping trees healthy and free from pests and diseases.