Thursday, May 30, 2013

Yellow pecan aphids and natural biological control

    When I travel to pecan meetings in the south, I often hear horror stories of massive yellow pecan aphid outbreaks in the early part of the growing season. At high populations, these sap feeding insects can literally drain the life out of pecan leaves.

Yellow pecan aphid, Monelliopsis pecanis
    Fortunately, I have never seen a springtime outbreak of yellow pecan aphids in a northern pecan grove. But this doesn't mean that yellow pecan aphids don't occur in our area. This spring, I've spotted a very light population of yellow aphids feeding on the underside of our pecan leaves (photo at left). In the photo, an adult yellow aphid is feeding on sap flowing through the main mid-rib of a pecan leaflet. Above the adult you can see a small yellow aphid nymph moving across the leaf surface in search of a good feeding spot.

Convergent lady beetle, Hippodamia convergens
    While scouting our trees, I also discovered one of  the main deterrents to yellow pecan aphid outbreaks . The convergent lady beetle is one of the most common, native, biological-control agents found in pecan-tree canopies (photo at right). Both adults and their larvae actively seek out and feed on yellow pecan aphids. 

     I stopped scouting for a minute just to watch a lady beetle scurry over the underside of pecan leaves in her endless search for prey (photo at right). I found it a fascinating lesson insect behavior.