Oak leaf phylloxera
50 host plants
You will see small yellow to orange aphid-like insects causing mid-summer scorching and yellowing on oak leaves, particularly Garry oak and English oak. Affected foliage browns and drops prematurely. Heavy infestations severely weaken trees over multiple seasons. Nymphs and adults feed on leaf undersides, leaving stippled, discolored feeding damage. The pest is most damaging to water-stressed oaks in the Puget Sound region.
No control is necessary to protect tree health. Natural predators including minute pirate bugs and lacewings usually keep populations in check. Avoid broad-spectrum insecticides that kill beneficial insects. Maintain tree vigor through proper irrigation during summer. Dormant oil may reduce populations for aesthetic reasons.