San Jose scale damage has been increasing this spring in northern Michigan, says Nikki Rothwell and Emily Pochubay of Michigan State University Extension (MSU) and John Wise of Michigan State University Department of Entomology.
San Jose scale feeds on the sap of trees, and can kill young trees in two to three years, population dependent. Large scale populations would be necessary to cause economic injury to healthy trees. Older trees may withstand more feeding damage, but would have dieback in the tops of trees, which would impact the cropping potential, they say.
“It is possible San Jose scale may behave differently on apple and cherry,” they write. “Hence, MSU Extension encourages consultants, scouts, and growers to trap for males to better predict when crawlers will emerge to best time spray applications.”
They encourage growers to understand the different control options for scale, because Lorsban can be phototoxic on sweet cherry foliage, and should not be used past petal fall in tart cherries.