Raul T. Villanueva, Extension Entomologist and Daniel Becker, Extension Associate for Vegetables/Fruit. Posted in June 4, 2019 edition of Kentucky Pest News.
Pecan samples brought to the University of Kentucky Entomology Laboratory in Princeton exhibited injury to new shoots and stems. These samples were collected by Darrell Simpson (Agriculture & Natural Resources Agent in Muhlenberg, KY) on behalf of a grower. The damage consisted of darkened holes near the bases of several shoots (Figure 1), along with leaf flagging (Figure 2). Further inspection of the samples, showed tunnels in the stems that extended into the pith caused by a legless larva (Figure 3). The larva had a yellowish color with a dark brown head and was approximately 10 mm in length. The combination of all these factors identified the hickory shoot curculio (Conotrachelus Aratus, Coleoptera: Curculionidae) as the culprit. Acrobasis shoot borers (Acrobasis spp.) cause similar damage during spring, but larvae are larger and have a dark olive-green coloration when mature.
The hickory shoot curculio is an insect well distributed in the USA: from Massachusetts to Florida and from Texas to Kansas. Damage by this insect is most common in the eastern USA; however, infestations can occasionally build up enough to warrant notice in the Midwest and south-central regions. Damage is often sporadic year-to-year, but if an outbreak occurs, more than 50% of shoots can be affected, severely diminishing nut production. Pecan orchards near wooded areas containing hickory trees or wild pecan stands are more susceptible to infestation.
Figure 1. Holes on pecan shoots (Photo: Raul Villaneuva, UK)
Figure 2. Leaf flagging caused by hickory shoot borer (Photo: Raul Villanueva, UK)