In California aphids are the most common pest in pecans. The yellow pecan aphid and black margined aphid (Monelliopsis pecanis and Monellia caryella; also known as the yellow aphid complex) pierce the leaf veins to extract photosynthates and water from the leaves, which can distort and stunt the growth of shoots and roots.

The black pecan aphid (Monellia caryaefoliae) inject a toxin into leaf tissue while feeding, which causes necrosis and leaf fall. Leaf drop causes poor nut quality and reduces bloom the next year. Black margined aphid also secretes honeydew which can harbor black sooty mold and attract ants (Call et al., 2006). Sooty mold can reduce photosynthesis more than 50% if accumulations are heavy. For more information regarding these aphids, refer to the UC Statewide IP Program: UC Pest Management Guidelines (link to http://ipm.ucdavis.edu/PMG/r609300211.html).

UC Statewide IPM Program: How to Manage Pests: Pecan
Includes Year-round IPM Program for walnuts, and University of California's official guidelines for pest monitoring techniques, pesticides, and nonpesticide alternatives for managing pests.