WSU Extension


Leaf scorch (marginal leaf necrosis) 
Leaf galls 
Linden aphid 

print version| pdf version| email url    
Caption: Linden aphids
Photo by: W. Cranshaw, Colo St Univ,
Linden(Tilia) : Linden aphid
(revision date: 3/22/2021)

Basswood or linden (Tilia spp.) trees planted along streets and in parking lots are commonly infested with linden aphids. The linden aphid feeds in colonies on the underside of leaves. Wingless aphids are green with black stripes or dots across the abdomen. Winged adults are similar in appearance, with black markings on the wings. Feeding damage from the linden aphid is usually minor, but can cause some leaf or shoot distortion if populations are very high. These aphids produce large amounts of honeydew, a sweet, sticky material. It can attract honeydew-feeding ants, which protect aphid colonies from predators. Honeydew may also promote an unsightly growth of black false sooty mold. Honeydew and false sooty mold can be a nuisance, particularly in street or parking lot plantings, but does not harm the tree.
Management Options

Non-Chemical Management
  • Wash trees with a strong stream of water to knock down aphids and wash away honeydew.
  • Hand-wipe or prune to control small, localized infestations (when practical).
  • Encourage aphid predators and parasites, including ladybird beetles, lacewings, and parasitic wasps. Avoid use of broad-spectrum insecticides which may kill these beneficial insects.
  • Provide proper nutrition. High levels of nitrogen in the foliage encourage aphid reproduction. Use a slow-release or low-nitrogen formula if fertilizer is needed.
Select non-chemical management options as your first choice!

Chemical Management

Do not make applications to blooming trees, as linden is very attractive to bees. Do not use soaps on trees stressed by drought or heat. Do not apply soaps in full sun or when temperature exceeds 90 degrees F. Dormant or delayed-dormant application of horticultural oils will help manage overwintering aphids and/or eggs. Homeowners should not make foliar applications to trees over 10 feet tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 feet tall. CAUTION: These pesticides are toxic to bees. To reduce risk to pollinating bees, make pesticide applications in the evening after bees are done working for the day. Do not apply on or near flowering plants.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • All Seasons Horticultural & Dormant Spray Oil Conc [Organic]
    Active ingredient: oil/pet distillate  |  EPA reg no: 4-80
  • Foxfarm Don't Bug Me Home & Garden Insect Spray RTU
    Active ingredient: pyrethrins, piperonyl butoxide  |  EPA reg no: 1021-1801-71996
  • Gordon's Dormant Oil Spray
    Active ingredient: oil/pet distillate  |  EPA reg no: 33955-458
  • Safer Brand Insect Killing Soap Conc II [Organic]
    Active ingredient: potassium salts of fatty acid  |  EPA reg no: 42697-60
  • Whitney Farms Insecticidal Soap for Organic Gardening [Organic]
    Active ingredient: potassium salts of fatty acid  |  EPA reg no: 67702-21-73327
  • This list may not include all products registered for this use.

+ Show larger images

Caption: Linden aphids
Photo by: W. Cranshaw, Colo St Univ,
Caption: Honeydew on linden from aphid infestation
Photo by: W. Cranshaw, Colo St Univ,