Ash Seed Weevils (Lignyodes spp.)
Solomon, J.D.; Leininger, T.D.; Wilson, A.D.; Anderson, R.L.; Thompson, L.C.; McCracken, F.I. 1993. Ash pests: A guide to major insects, diseases, air pollution injury and chemical injury. Gen. Tech. Rep. SO-96. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station. 45 p.
Three ash seed weevils, Lignyodes bischoffi (Blatchley), L. helvolus (LeConte), and L. horridulus (Casey), occur throughout the United States and Canada. These weevils feed on the seeds of ashes and lilac. Over 60 percent of the ash seeds in the Northeastern States and up to 95 percent in the Great Plains may be destroyed.
Identifying the Insects
Adults are elongate-oval and 2.3 to 4.0 mm long. The pronotum is narrower than the base of the elytra, and the snout is curled with elbowed antennae. The pronotum and elytra are covered with brown to yellow scales. Color patterns distinguish the species. Larvae are white and legless with a curved body and brown head.
Identifying the Injury
Infested seeds are difficult to distinguish with the naked eye. With magnification, small, raised, puncture marks partially covered with dark excrement can be observed on the seed coat. Cutting open the seed will reveal the feeding larvae. Small oval to irregular holes are left in seeds by emerging larvae.
The weevils overwinter as larvae in the soil or in fallen seeds. Pupation occurs in the soil during spring and summer and lasts about 12 days. Adults emerge during July and August and are present until autumn. Females deposit eggs singly within the seed and seal the openings with excrement. Eggs hatch in 2 days, and the larvae completely consume the seed contents. Mature larvae exit the seed during fall, winter, or spring and burrow into the soil to pupate. There is one generation per year.
Natural controls keep most populations in check. Direct controls are rarely justified.