Friday, May 9, 2014

Dry Spring weather promotes sawfly populations

   Today, we were out working in the pecan grove when we spotted evidence of sawfly larvae feeding on pecan foliage. It is easy to spot. Just look up into a pecan tree's canopy and if you see leaves with a series of holes chewed into leaf blades, you can bet you have had sawfly larvae feasting on this year's new growth (photo at right).

   To find out if you have a active population of feeding sawflies, look on the underside of the foliage. You should find a small green worm chewing holes in the foliage (photo at left).
At this point we are not seeing enough larvae to justify a pesticide application but we need to watch our orchard  carefully over the next week or so to make sure we don't get surprised by a major outbreak of this insect.
   Sawflies are not actually flies at all. The larvae we see eating pecan foliage are actually the juvenile form of a member of the wasp family known by the scientific name, Periclista marginicollis. Although the larvae pictured at right looks like a caterpillar, note that this worm has 3 sets of true legs near the head followed by pair of prolegs on every body segment thereafter. Caterpillars or the larvae of butterflies and moths also have prolegs but not on every body segment behind the true legs.
    Sawflies adults emerge in the spring and produce a single generation per year. When larvae fully mature, they drop to the ground and pupate in the soil. I have always found that dry spring weather conditions seem to promote sawfly populations.