The twig girdler, Oncideres cingulata, is a mottled grayish brown longhorned beetle with long antennae and is about an inch long. Eggs are flattened, elongate cylinders. The grubs are tiny and chubby at first, but later develop into typical, slender roundheaded wood borers. Pupae occur inside the fallen twigs. Pupae and somewhat elongate with their antennae curled symetrically on the lower surface. Twig girdlers are pests of pecan and hickory, and to a lesser extent oaks and several other hardwood trees that have twigs with smooth bark such as dogwood, elm, hackberry, honeylocust, linden, persimmon, poplar, redbud, and flowering fruits.
Adults emerge in late August to early October and feed on tender bark and tips of twigs of host trees. They live 6 to 10 weeks. Female beetles then chew around and around twigs and small branches of host trees. Females then insert their eggs under the bark usually at the base of a leaf along the girdled portion above the girdle. Females deposit 50 to 200 eggs each, that hatch in about 3 weeks. Girdling extends through the bark and well into the wood in a complete circle around the stem that leaves only a thin column of center wood attached. Close inspection of the severed twigs reveals tiny egg niches near bud scars and many tiny grooves at the girdled end made in the bark by the female beetles. Large trees usually sustain the most girdling, but young trees are sometimes heavily damaged. Since the twigs are girdled while the leaves are present, severed twigs retain dead leaves for some time. It is a pest of pecan and hickory, and to a lesser extent several other hardwood trees. It is not uncommon to see the ground under infested trees littered with girdled twigs. After overwintering, the larvae grow rapidly in the spring and tunnel toward the severed end of the twig by feeding only on the woody portion and leaving the bark intact. A few small circular holes are made in the bark to eject pellets of frass and excrement. The mature larvae close off the gallery with shredded fibers to form a pupation chamber. Pupation occurs during August and September and lasts 12 to 14 days. The new adult chews a circular hole in the bark to emerge. There is one generation per year. Girdling affects the beauty and aesthetic quality of ornamental plantings. This type of injury causes the development of many offshoots that adversely affect the symmetry of the tree. Repeated girdling of terminals causes forks, crooks, and other stem deformities in young timber plantations as well as in natural reproduction. With pecans, the fruiting twigs of heavily infested trees are often reduced, resulting in lower nut yields the following year or years. Pecan nurseries located close to heavily infested wood lots occasionally suffer considerable loss from girdled seedlings.
Insecticide applications are rarely justified or practical in landscapes. Insecticides may be necessary to prevent damage from heavy infestations in some hardwood tree nurseries. These may be applied once or twice in September and again in October as a protectant to reduce the majority of the twig girdlers. Natural controls are important in keeping twig girdler populations low. Desiccation of the eggs is apparently the greatest single mortality factor. The parasites, Eurytoma magdalidis, Iphiaulax agrili, and Horismenus sp., and a checkered flower beetle, Cymatodera undulata all help reduce girdler populations. In landscapes, orchards, and nurseries, the severed twigs on the ground as well as those lodged in the trees should be gathered and destroyed during the fall, winter, and spring while the eggs and grubs are still in the twigs. If nearby plantings have a history of serious damage, the same practice should be followed in nearby wood lots containing oak and hickory. Twig destruction should greatly reduce populations in one or two seasons.
- Twig Girdler. Rice, M. E. and B. Dress. No Date. Field Guide to Common Texas Insects, Texas A&M AgriLife Extension.
- The Twig Girdler: A Guide to Recognition and Habits in Alabama. Hyche, L. L.1995. Auburn University Entomology and Plant Pathology Outreach.
- Twig Girdler and Twig Pruner. Barrett, B. A. No Date. University of Missouri Extension, Department of Entomology.
- Twig Girdlers and Twig Pruners - Trees. Anonymous. No Date. University of Maryland Home & Garden Information Center.
- Extension Plant Pathology Publications and Factsheets
- Horticultural Science Publications
- North Carolina Agricultural Chemicals Manual
For assistance with a specific problem, contact your local Cooperative Extension center.
Publication date: Oct. 20, 2001
Revised: Oct. 17, 2019
Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your local N.C. Cooperative Extension county center.
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