Tuesday, August 19, 2014

Pecan leaves covered in honeydew

Honeydew on pecan leaflet
   Have you noticed a shiny and sticky substance covering your pecan leaves this summer (photo at right). That  substance is called honeydew and it is excreted by black-margined pecan aphids feeding on the leaves. 

   Turn a honeydew-coated leaf over and you will find several aphids lined up along the major leaf veins (photo below). Immature aphids are yellow and wingless. Adult aphids also yellow but have clear wings with a streak of black along the outside edge.
Black-margined aphids feeding on pecan

Harmonia lady beetle
Lacewing egg attached by a silken thread
Spider hiding in webbed nest between nuts
   Fortunately we have several beneficial insects in the pecan grove that feed on aphids helping to control this sap feeding insect. Among the most active aphid predators are the lady beetles and the lacewings. Pecan canopies are also populated by a large number of spiders that will feed on aphids.     
   In most cases, we do not try to control black-margined aphids with insecticides. Over-use of insecticides usually leads to the elimination of beneficial insects, creating a huge rebound explosion in aphid populations.