Have you seen flagging leaves and shoot dieback on this year's new pecan shoots (photo at right). If you have, you are most likely seeing an attack of the hickory shoot curculio.
After resting dormant all winter in ground cover thatch, adult curculios (
Conotrachelus aratus) become active in the spring as pecan shoot growth commences. When the first leaf on new pecan shoots is about one half expanded, female curculios start searching of locations to lay eggs.
Hickory shoot curculio females use their mouth parts to carve a moon shaped depression into the base of a leaf petiole (photo at left). In that depression she will lay an egg. The larvae that emerges from the egg will first tunnel into the leaf petiole causing the leaf to wither and die. It will continue to feed by tunneling into the center of the new shoot making its way towards the terminal, often killing the entire shoot.
If you see signs of hickory shoot curculio activity, cut open an infested shoot and you should find a white, legless larvae with a red head (photo at right).
Once the larvae hatches and begins to burrow into pecan shoot tissue, it is impossible to control this pest with an insecticide. In other words, once you see the damage it too late to take action this year. If your pecan grove has a history of curculio attack plan on controlling adults early next spring.
You will probably never see an adult hickory shoot curculio in the field (photo at left) but watch the development of springtime pecan shoot growth to time an insecticide treatment. Spray when the first leaf on the new growth starts to unfurls all its leaflets.
Hickory shoot curculio is one of those sporadic pecan pests that seem to appear out of nowhere and then a couple of years later disappear altogether. I've only seen a few curculio infestations that warrant chemical control. It seems that naturally occurring biological control agents usually keep this pest in check.
