Pesticide applications should target nymphs because eggs are not affected. Determine this stage by looking for spiny nymphs near egg masses on leaf undersides and monitoring to determine egg hatch. Short residual materials, like soaps, oils, or pyrethrins, can be effective on nymphs if coverage is adequate. Topical foliar applied materials can also provide effective control. Each year around this time we receive phone calls and samples inquiring about cupping and curling of tulip poplar leaves on well-established trees.
Similar symptoms are absent on neighboring trees and shrubs.
This foliar symptom is most often attributed to root stress brought on by a variety of noninfectious, environmental and site related factors. Damage to cambial tissue from temperature extremes, as well as stress brought on by hot, dry winds may also contribute to leaf cupping and curling. Make sure the tree receives at least one inch of water per week, and fertilize according to the instructions given in the bulletin HO-140, Fertilizing Woody Plants. Be aware that although no other plants in the vicinity of the tulip poplar trees may be observed to exhibit similar foliar symptoms it is important not to automatically rule out growth regulator-type herbicides. If the neighboring vegetation consists of plants that are less sensitive to growth regulator-type herbicides than tulip poplar, leaves on those other plants may not exhibit the cupping symptoms.