Friday, May 15, 2015

June beetles cut off new growth

   Last week, we experienced several days when early evening hour temperatures remained in the low 70's. That's when I heard the familiar sound of large "June" beetles crashing into the windows of my house starting shortly after sunset.  I looked through the window glass and spotted a European chafer crawling on the sill. After spotting this insect, I knew that I could go outside the next morning and find new leaves and shoots chewed off young pecan trees (photo at right). I've written about this pest in an earlier post, but this week I wanted to talk further about the adult beetle behavior and why they only damage young pecan trees.

    The European chafer produces one generation per year. Female beetles lay their eggs in the turf  and C-shaped grubs that hatch from these eggs spend all year feeding on the roots of grasses. Each spring larvae pupate and become adult beetles. These beetles emerge from the turf during early evening hours and swarm to low lying tree branches or shrubs. By cutting off tender leaves and shoots, the European chafer creates an ideal place for additional beetles to land facilitating the search for a suitable mate.
   European chafers are ground dwelling insects so when then fly onto young pecan trees they generally migrate to lower limbs. In the photo at left, you can see that the lowest two limbs of this tree have been attacked by beetles while the upper portion of the tree is untouched. As pecan trees grow larger and lower limbs are pruned off, European chafers will no longer present a problem because these insect can't stand heights.  
    Spring emergence of adult beetles lasts about 2 weeks. At my location, emergence is trailing off and will be over soon.