By George Giltner, Adv. Master Gardener
Fall is the time of year to notice yellow-necked caterpillars, Datana spp. The head is black followed with a yellow to orange neck. The body is black with 4 longitudinal yellow lines on each side. White long hairs cover the 2-inch mature caterpillar body. A behavior characteristic, which also helps to ID this caterpillar, is the “C” or “U” shaped arching of the body when it is disturbed. Another behavioral characteristic is their group feeding, as large numbers are found on individual branches.
Check your blueberry bushes at least every two weeks from August till late fall. Treat bushes with Bt or Spinosad, or mechanically remove, or prune for control. These voracious feeders can entirely defoliate small bushes. This extensive defoliation will retard the growth of the blueberry bush, but it usually does not kill it due to late season leaf fall anyway. However if repeated yearly defoliations are allowed to occur, the bushes may die. In late fall the caterpillars leave the foliage, enter the soil and pupate for the winter.
Other trees and bushes affected include pecans, hickories, walnuts, apple, maple, elm, cherry, witch-hazel, and azalea. Usually no treatment is required for these trees and bushes due to natural predators including birds and predatory insects. Tachinid flies, especially Winthemia datanae, is the most common predator (Craighead, F.C. 1949. Insect Enemies of Eastern Forests. USDA Misc. Publ. #657. 679pp.).