Life-History of the Pecan Twig Girdler
Journal of Economic Entomology 9(1): 110-115
Oncidefes texana may cause serious damage to pecan 'trees, ' the cultivation of which has become an important industry in Texas, by the girdling of the branches for the purpose of egg-laying. ''This beetle has also been found on persimmon, elm, hickory, maple, pear, peach, etc. Oviposition begins after the twig has been girdled1; the central portion is generally left intact, but the weight of the branch is often sufficient to cause it to break off. Eggs are laid singly, or rarely in groups of three or four, at the base of the leaf buds, in an incision made in the bark. During the oviposition period, both male and female feed on the soft wood at the base of the leaf buds at the extremity of the branch. When nurseries are adjacent to forests, severe damage is often caused by migration of the adults from the surrounding trees. Females emerge from 25th August until the beginning of October. Oviposition begins from 12 to 29 days later, and may continue until December. About 175 eggs are deposited on an average by each female. The larva, which hatches in from 17 to 30 days, hollows out a cavity in the branch and feeds throughout the winter. The larval stage lasts from 288 to 328 days. Pupation occurs late in August or early in September, and the pupal stage, lasting for 12 or 14 days, is passed in the pupal burrow. The method of control by gathering fallen twigs and burning them in order to kill the larvae is practicable only where a pecan orchard is not situated near other trees. Experiments with lead arsenate proved effective in preventing migration to the pecan trees. In the discussion following, it was stated that the female usually oviposits in the main twigs, the girdles being cut at a distance of about 2 feet from the trunks of the smaller trees. In breeding experiments, moisture proved to be an important factor. A small number of larvae survived in branches which remained on the ground. Beetles were hot observed girdling branches which sloped downwards. A considerable percentage of adults were parasitized by a Tachinid fly.