Monday, June 13, 2011

Pecan leaf phylloxera

   During this time of year you may notice small, yellow galls growing between the veins of pecan leaves (photo at left). These galls are created by the pecan leaf phylloxera.
     Phylloxera are small, aphid-like insects that overwinter in the rough bark of pecan trees. In early spring, just when the first new leaf bursts from expanding buds, phylloxerans crawl out onto the emerging leaves and start to feed. As leaves expand,  phylloxerans secrete a substance that causes pecan leaves  to grow a galls around each insect.

    Once inside the gall,  phylloxerans produce two generations of offspring that all feed on plant sap from inside the gall. In June, the gall opens up on the underside of the leaf (photo at right shows galls cracking open ) to allow winged adults to fly out of the gall and mate. Mated females then hide under rough bark where their bodies become filled with the eggs that will start next year's population of phylloxerans.
    If phylloxera galls become so numerous they seriously distort leaves, you will see early defoliation of infested leaflets starting in July. To control phylloxera, an insecticide should be applied early in the spring at leaf burst before galls start to form.