The non-native oak lace bug is causing increased damage to Oregon white oak trees, according to the Oregon Department of Forestry.
While the oak lace bug has been in Oregon since 2015, their damage has been more substantial this year.
“Insects can have ‘wave’ years in which populations increase for a variety of reasons ranging from increases in fitness such as from an increase in quantity or quality of food sources to a decrease in predators to a change in conditions,” said Christine Buhl, forest entomologist for the Oregon Department of Forestry. “Summer temperatures were extended late this year so I hypothesize that this extended the active feeding window so oak lace bug populations just had more time to keep feeding/causing more damage.”
The oak lace bug is native from southern Canada to the Eastern, Central and Southern United States. In Oregon, they are mostly a pest of urban oaks but can infest related trees.
The insects are an eighth of an inch long and transparent when adults. They can be found on the underside of leaves, where they suck plant juices from photosynthetic cells containing chlorophyll. This causes leaf yellowing. Only leaf damage has been noted from this insect, which means there is no damage to buds or twigs, Buhl said.
Yellowing and browning of Oregon white oak trees can be common in the fall due to other factors like ongoing droughts and hot weather and normal pest attacks. Despite damage from the oak lace bug and other pests, white oaks will reflush the next year as normal.
Typically, oak lace bugs are only an aesthetic pest that aren’t persistent yearly, so treatment of the bugs is usually not advised. There are insecticides that can be used to treat active infestations or prevent infestations, but Buhl said they are expensive and toxic to predators and insects that are helping to reduce populations of the oak lace bug. Fertilizing is also not advised as it will not help yellowing or browning leaves.
The insect can bite, but it typically is a single “taste-test” bite that doesn’t cause more than a mild sting, similar to an ant bite, Buhl said.