How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Adult Fuller rose beetles are brown, flightless snout beetles and are all females that reproduce without mating. They can be distinguished from two other snout beetles that occur in California citrus groves but do not cause damage: viewed from the top the Fuller rose beetle head and bulging eyes are different than the cribrate weevil, which has a teardrop-shaped head with closely spaced eyes, and viewed from the side the Fuller rose beetle's snout is less sharply pointed to the ground than that of the vegetable weevil.

The Fuller rose beetle has one generation a year. Eggs are laid in a mass of several dozen on fruit, especially underneath the button or in cracks and crevices in the tree. When eggs hatch, larvae drop to the ground and live in the soil where they feed on roots of citrus for 6 to 10 months. They pupate in the soil and the adults emerge 1.5 to 2 months later. Adults are flightless and reach the canopy by climbing up the trunk or branches that touch the ground or vegetation.

DAMAGE

The beetle itself does not generally cause economic damage in citrus but the presence of eggs on fruit exported to Japan used to be a quarantine concern. Since Fuller rose beetle has been found in Japanese citrus groves, this is no longer a concern. Fuller rose beetle adults feed along the margins of citrus leaves, creating notches and leaving a characteristic sharp, ragged appearance. Normally, they are not a concern except on topworked trees where the beetles will feed on new buds or if a young tree is planted in a mature grove and beetles concentrate their feeding on the new growth of that tree.

MANAGEMENT

If management of Fuller rose beetles is necessary (i.e., should it become a quarantine concern in other countries), there are three primary strategies: (1) skirt pruning with trunk treatment; (2) preharvest foliar sprays, or (3) season-long suppression with foliar sprays for 1.5 to 2 years. Use skirt pruning and trunk treatment in orchards with a history of Fuller rose beetle. As an alternative, one or two preharvest foliar sprays may be applied to prevent exported fruit from being infested with viable eggs.

Biological Control
The egg parasite, Fidiobia citri, can parasitize up to 50% of each egg mass. Parasitized eggs are a dark gold color and they may persist long after unparasitized eggs have hatched.

Cultural Control
If Fuller rose beetle has been a problem in your orchard in the past, the best strategy is to prevent the flightless adults from reaching the canopy by using skirt pruning and trunk treatments. Skirt prune trees 24 to 30 inches above the ground to prevent adults from reaching the canopy and apply sticky material to the trunk. Sticky material can be expected to last 2 to 10 months, depending on wash-off by sprinklers and the amount of dirt and leaf contamination. Sticky material will also control ants, and if it contains tribasic copper sulfate, it is effective against brown garden snail as well.

Some concern has been expressed regarding the application of sticky polybutene materials directly to the trunk of citrus trees, especially if multiple applications are applied to the same area of the trunk. The sticky material can be applied on top of a tree wrap but this is both laborious and expensive. Trials to date have failed to show serious phytotoxicity (minor bark cracking has been seen in a very small number of cases) except in situations where damage is associated with sunburn—i.e., where the banded area is exposed to direct sunlight (especially a concern on topworked trees or on young trees which have a very thin cambium layer and are more susceptible to damage). On young or topworked trees, apply sticky materials only on top of a tree wrap to protect the tree from sunburn.

Organically Acceptable Methods
Biological and cultural controls, including the application of sticky materials are acceptable organic methods.

Monitoring and Treatment Decisions
If Fuller rose beetle damage occurs in an orchard, sample for adults from July to November by shaking or beating branches onto a sheet or tray. If beetles are found, sample fruit for egg masses, especially in the areas where adult feeding damage has been found. Sample a minimum of 500 fruit in a 10 acre block (5 fruit per tree from 10 trees per acre). Select fruit from chest height from a different quadrant of the canopy. Clip the stem 2 inches from fruit, then hold the stem and twist off the button. Look for egg masses on the underside of the button end and on the fruit where it was covered by the button. If the fruit is to be shipped to Japan, infestation levels should be less than one fruit infested with a viable, unhatched egg per 1,000 fruit sampled at harvest.

Treat 600 degree-days (accumulated above 51°F lower threshold) before harvest. This can range from 1 to 4 months, depending on the weather. During cool weather, retreatment may be necessary.

• Summary of Important Links

IMPORTANT LINKS

• Degree-day calculator
• Degree-day table

PUBLICATION

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
Insects, Mites, and Snails
E. E. Grafton-Cardwell, Kearney Agricultural Center, Parlier
J. G. Morse, Entomology, UC Riverside
N. V. O‘Connell, UC Cooperative Extension, Tulare County
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
C. E. Kallsen, UC Cooperative Extension, Kern County
D. R. Haviland, UC Cooperative Extension, Kern County
Acknowledgments for contributions to Insect, Mites, and Snails:
J. Barcinas, E. S. I., Corona, CA
R. Dunn, Badger Farming County, Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
H. Griffiths, E. S. I., Corona, CA
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
T. Roberts, E. S. I., Corona, CA
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA
K. Godfrey, USDA Biological Control, Sacramento
D. Headrick, California Polytechnic State University, San Luis Obispo
B. Faber, UC Cooperative Extension, Ventura County
J. Kabashima, UC Cooperative Extension, South Coast Research and Extension Center

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