Friday, June 10, 2011

Walnut caterpillar eggs

    I was doing some summer pruning a couple of days ago and spotted this egg mass (at left) on the underside of a leaflet. These are the eggs of the walnut caterpillar (Datana integerrima), a major defoliating pest of pecans.
    When I see one of these egg masses, I carefully observe the eggs for a while waiting to see if any parasitic wasps show up. The tiny black wasps, Trichogramma minutum, seem to dance over the egg mass and lay their own eggs inside the caterpillar eggs. These wasps usually keep walnut caterpillar in check, but unfortunately, I didn't see any on this egg mass.
    We will need to keep close tabs on walnut caterpillar this summer, watching of signs of a population outbreak that requires an insecticide treatment.