[Image: Yellow Pecan Aphids]
The sticky substance on the leaves is honeydew, the result of feeding on the leaves by aphids. Two species of aphid are responsible for the honeydew: the yellow pecan aphid and the black-margined aphid. Both species can produce large amounts of honeydew. The honeydew coats the leaves and serves as a medium for the growth of the sooty mold fungus, which shades the leaves and greatly reduces photosynthesis. Studies have also shown that feeding by these aphids reduces chlorophyll production, leaf size and stem and root growth. Leaflet loss can also occur during heavy infestations. Bees, wasps and ants may be attracted to trees with heavy honeydew production.
More detailed information on the distribution, description, life cycle, damage, and control of these aphids and on sooty mold can be found on the Yellow Aphids fact sheet on the Entomology page and in the Pecan Disease Synopsis on the Plant Pathology page of the Pecan Station website.
Question answered by Dr. Mike Hall, Pecan Research-Extension Station entomologist.