How to Manage Pests

Pests in Gardens and Landscapes

Fuller rose beetle—Naupactus (=Asynonychus) godmani

This snout beetle, or weevil (family Curculionidae), feeds on many woody plants. Hosts include acacia, avocado, box elder, citrus, oak, photinia, Prunus and Pyrus species, Rhaphiolepis species, and rose.

Identification

Adults are brown to gray, hard-bodied weevils about 3/8 inch long with bulging eyes. The shape and orientation of the head distinguish Fuller rose beetle from two other brown to grayish snout beetles that are also common in California, the cribrate weevil (Otiorhynchus cribricollis) and vegetable weevil (Listroderes difficilis).

Eggs of Fuller rose beetle are yellowish, about 1/25 inch long, and occur in a mass of several dozen. They commonly occur in cracks and crevices of tree bark. In citrus, eggs can be laid underneath the sepals (button) of fruit.

Larvae are plump, oblong, whitish to yellow, and legless. They have a brown head and grow up to 1/2 inch long.

Life cycle

Weevils develop through four life stages: egg, larva, pupa, and adult. All Fuller rose beetles are females that reproduce and lay eggs without mating. After hatching, larvae drop to the ground and live in the soil where they chew and feed on roots for about 6 to 10 months. Mature larvae pupate in the soil for 1-1/2 to 2 months.

Adults emerge from pupae mostly during summer and fall. They feed at night. During the day they seek shelter in organic litter on the ground. Adults are flightless and reach the canopy by climbing up the trunk or branches that touch the ground or vegetation. Fuller rose beetle has one generation per year.

Damage

Larvae chew and feed on roots, but generally this does not threaten plant health. Adults chew along the margins of leaves, creating notches and ragged, sharp edges. Adult feeding is not a concern for plant health, except perhaps when the weevil populations are high and feeding on young hosts or plants that have been extensively pruned and are producing new buds and leaves. Adults also may chew blossoms, which along with leaf chewing reduces the aesthetic quality of plants.

Solutions

A tiny wasp (Fidiobia citri, Platygastridae) commonly parasitizes eggs of Fuller rose beetle. The Fidiobia adult is a mostly black wasp less than 1/25 inch long. The adult female lays one egg inside each weevil egg. Fidiobia can parasitize up to 50% of the eggs in each Fuller rose beetle egg mass. In contrast to the pale yellow to whitish color of unparasitized eggs, parasitized eggs turn dark gold then blacken shortly before the adult Fidiobia emerges; parasitized eggs may persist long after unparasitized eggs have hatched.

Feeding by Fuller rose beetle does not seriously harm established, otherwise healthy woody plants and generally can be ignored. Provide proper cultural care to keep plants vigorous and better able to tolerate insect feeding. Trim branches that provide a bridge to other plants or the ground and apply a 6-inch band of sticky material (e.g., Tanglefoot) to trunks to prevent the flightless adults from climbing up to feed on foliage. First wrap the trunk several inches wide with landscape fabric or plastic, then apply the sticky material on top the wrap to avoid potential bark injury from the sticky material. Periodically replace wraps to prevent growth-restriction damage to trunks.

If adult populations are high, trapping may help provide some control. No insecticides are recommended for this insect in gardens and landscapes.

Adapted from Integrated Pest Management for Citrus and Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).

Chewing damage from adult Fuller rose beetles.
Chewing damage from adult Fuller rose beetles.

Adult Fuller rose beetle.
Adult Fuller rose beetle.

Eggs of Fuller rose beetle under citrus sepals.
Eggs of Fuller rose beetle under citrus sepals.

Larvae (left) and pupa of Fuller rose beetle, exposed.
Larvae (left) and pupa of Fuller rose beetle, exposed.

 


Statewide IPM Program, Agriculture and Natural Resources, University of California
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