Yellow and black pecan aphids are small, soft bodied insects with piercing sucking mouthparts.  Yellow aphids are characteristically yellow in appearance.  Black aphids are a “dull” black in color.  During the process of feeding they excrete a clear sugary material called “honeydew”.  Honeydew is the substance that gives pecan trees a shiny glistening appearance during epidemic aphid infestations.  If you have parked a car under a pecan tree and noticed the car to have a sticky feel to it, then you know what honeydew is.  Honeydew serves as a food source for  sooty mold, which can cover the pecan leaves when humidity is high.  Sooty mold can reduce photosynthesis which in turn reduces the pecan tree’s ability for adequate carbohydrate production.

Yellow and black pecan aphids can significantly reduce pecan yields.  Both aphids suck photosynthates from leaves, excrete “honeydew’, and reduce the flow of nutrients to nuts.  Damaging infestations of yellow aphids can cause whole leaves to turn yellow and possibly shed.  Black aphid damage is characterized by small, chlorotic areas on the leaflets.  Heavy infestations cause rapid leaf shed.  Both aphids can cause premature leaf shed, reduced nut quality, and subsequent yield reductions the following season.

Consider treatment when infestations of yellow pecan aphids exceed 25 per compound leaf, indicating the onset of an outbreak.  Scouting the orchard on a 4 to 5 day schedule will determine if yellow pecan aphid numbers are increasing or decreasing and dictate the need for insecticide treatment.  The need for treatment should not be based on the amount of honeydew alone, as infestations often decline rapidly (“crash”) because of weather or physiological effects.  Black aphids usually do not require controls until late season.  After mid-July, black aphids should be treated when there are an average of two to three per compound leaf.