Aphid
Aphidoidea
447 host plants
Last updated
During growing season you will observe sticky honeydew coating leaves and twigs, followed by sooty mold that blackens foliage. Look for clusters of soft-bodied, pear-shaped insects in green, gray, or black on new growth and shoot tips. On conifers like firs and spruces, larger blackish conifer aphids (Cinara spp.) create obvious colonies on main branches.
Spray infested areas forcefully with water; repeat every few days for light infestations. Release ladybird beetles, lacewings, or parasitoid wasps which naturally control aphids when broad-spectrum insecticides are avoided. Apply insecticidal soap or horticultural oil when cool (below 85F). Neem oil requires repeated applications every 7 to 10 days. Reserve pyrethrin sprays for severe outbreaks.
Quick Reference
Monitoring & Action
Scout new growth weekly for early colonies (March-April). By week 2-3, look for natural enemies: ladybug larvae (tiny, elongated, black and orange), syrphid fly larvae (green maggots), parasitoid mummies (tan, swollen, papery aphids). Mummy ratios relative to live aphid counts indicate biocontrol activity; predator presence typically forestalls the need for chemical intervention.
Establish 3-week waiting period from first detection of colonies. If by week 3 predator populations (lady beetles, lacewings, syrphids) are visible and mummy counts are rising, allow natural control to proceed - do not spray. Treat only if: (1) populations are growing despite 3 weeks' waiting, (2) mummy ratios are flat, (3) plant shows stress. For heavy aphids on young trees, water spray dislodges without harming predators.
Aphids feed by inserting piercing-sucking mouthparts into phloem tissue and extracting plant sap. Damage includes curled, distorted, or yellowed leaves; stunted shoot growth; and reduced fruit quality. Honeydew excretion coats leaf surfaces and supports sooty mold growth, reducing photosynthesis and aesthetic quality. Some species transmit plant viruses (e.g., bean yellow mosaic, plum pox, strawberry mottle). Heavy infestations on young plants can cause significant growth reduction; established plants typically tolerate moderate populations without lasting damage.
Cultural Controls
- Many parasites and predators attack aphids.
- Monitor the proportion of aphid mummies to unparasitized adults, and the number of predators such as lady beetles.
- If the biocontrol agents appear to be gaining control, avoid sprays which would disrupt this system.
- Most products available for aphid control are highly disruptive to natural enemy populations.
- Controlling weeds late in the season may help reduce overwintering populations.
- Aphid populations...
Host Plants (447)
Sources & References
Primary: PNW Insect Management Handbook
- WSU HortSense — multiple aphid fact sheets
- Dixon, A.F.G. (1998). Aphid Ecology. Chapman & Hall.
- UC Davis IPM: Aphids