How to Manage Pests
UC Pest Management Guidelines
Fuller Rose Beetle
Scientific name: Naupactus (Asynonychus) godmani (syn. Pantomorus cervinus)
(Reviewed 9/16, updated 9/16)
In this Guideline:
DESCRIPTION OF THE PEST
Adult Fuller rose beetles are brown to grayish snout beetles (weevils, family Curculionidae), about 0.36 inch (9 mm) long. Adults are all females, which lay eggs in clusters of several dozen in crevices on the tree or under loose bark. Larvae drop to the ground and feed on weed or tree roots, but larval feeding does not damage trees. Overwintering is as grubs that pupate beginning about June to July. Most adults emerge from June through October, but a few will emerge each month throughout the year. They feed for about 2 weeks before laying their first eggs. Feeding and egg-laying can continue into winter. There is one generation each year.
Fuller rose beetle is an occasional problem in young avocado plantings. It can also damage top-worked, recently grafted, or severely pruned trees that have relatively little mature foliage and an abundance of developing immature leaves. Fuller rose beetle usually is common only on avocado growing near citrus or other preferred hosts.
Fuller rose beetle adults chew leaf margins, causing a ragged, notched, or serrated appearance that is quite different from damage caused by other pests such as snails. Most chewed leaves are on lower branches because adults cannot fly and must climb trunks and branches to reach foliage. Leaf chewing on older trees with a well-developed canopy is not economically important. There is no evidence that root feeding reduces yield and research has not been done to determine if root feeding predisposes trees to infection by Phytophthora.
During late winter or early spring, apply a sticky barrier to trunks to exclude weevils if they may be a problem. Encircle a smooth section of trunk with a flexible wrap or tape and apply the sticky material on top to prevent direct contact with, and injury to, bark. A parasitic wasp (Fidiobia citri, family Platygastridae) parasitizes up to 50% of Fuller rose beetle eggs in citrus. Parasitized eggs darken and may persist long after unparasitized eggs have hatched. This parasite's importance in avocado is unknown.
Starting in June, inspect susceptible young or top-worked trees for leaf notching made by newly emerged adults. Be aware that caterpillars, earwigs, June beetles, grasshoppers, and snails also chew avocado leaves. Larvae and pupae of the exotic Diaprepes root weevil (Diaprepes abbreviatus) resemble Fuller rose beetle and adults of both species chew leaves. Be certain to identify the cause of problems before taking action. If suspected Diaprepes root weevils are found, notify agricultural officials as prompt management action may be warranted.
UC IPM Pest Management Guidelines: Avocado
J. G. Morse, Entomology, UC Riverside
Acknowledgment for contributions to Invertebrates:P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
M. Blua, Entomology, UC Riverside
P. Oevering, UC Cooperative Extension, Ventura County
D. Machlitt, Consulting Entomology Services, Moorpark, CA
T. Roberts, Integrated Consulting Entomology, Ventura, CA
B. B. Westerdahl, Nematology, UC Davis