A scale insect problem can be seen on trees in the form of small brown bumps, which look like small oyster shells attached to the branches and trunk of the tree. Over time, the scale ‘shells’ will reproduce and spread over large areas of the tree’s woody branches. The scale gradually attacks the tree by sucking sap and nutrients from the tree and, over time, heavily infected areas will experience die-back.
Since scale insects do not move and have no eyes or legs, they are often overlooked as an insect or pathogen. In the spring, small, almost invisible nymphs emerge from under the female shells and move to infect new areas of the tree. This is the only time in the life-cycle of scale that the insect moves.
Recommended Steps to Control Oystershell Scale
To control scale insects effectively and to limit damage, Horticultural Oil Insect Spray should be sprayed on the tree in late winter and again before spring bud break begins. The Horticultural oil serves to suffocate the scale and eggs. In the spring, if the crawling nymphs are present, spray the trees with Bug Buster Pyrethrin Insect Spray to prevent the new nymphs from further infecting the tree.