How to Manage Pests

UC Pest Management Guidelines

DAMAGE
These ants feed on honeydew excreted by soft scales, mealybugs, cottony cushion scales, whiteflies, and aphids. As part of this relationship, they also protect these insects from their natural enemies, thus interrupting biological control of the honeydew-producing pests. In the process of keeping most natural enemies away, they also protect other pests, such as California red scales, that profit from the lack of natural enemies. Fire ants feed on the twigs and bark of young trees, sometimes girdling the trees.

MANAGEMENT
Ants can be extremely disruptive to an IPM program. The Argentine, native gray and fire ants can be controlled with cultural methods such as pruning and the use of sticky materials applied on top of a tree wrap to the bark as well as with insecticide treatments.

Biological Control
No effective natural enemies of the Argentine ant are known.

Cultural Control
Skirt prune trees, i.e., remove branches within 12 to 30 inches of the ground, and apply sticky material to the trunk to prevent access to the trees by ants. Use polybutenes; oil-based materials may cause phytotoxicity and should not be used. Sticky material should last from 2 to 10 months and will also prevent the access by Fuller rose beetles. If the sticky material contains tribasic copper sulfate, it will also control brown garden snails. The persistence of sticky material can be increased by applying it higher above the ground to reduce dust and dirt contamination and to decrease irrigation wash-off.

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). Do not apply sticky materials to young or topworked trees.

To prevent bark damage by southern fire ants, plant trees with the bud union about 6 to 8 inches (14-19 cm) above the soil surface. Irrigate as needed, but avoid applying water to the trunk and do not allow water to pond near the trunk. Periodically examine bark under trunk wraps of several young trees. If gum is observed, inspect and if necessary, treat for Phytophthora gummosis (see DISEASE section). Bordeaux whitewash helps prevent gumming, which attracts ants.

Cultivation also reduces ant populations, but may create so much dust that biological control of other pests is disrupted.

Organically Acceptable Methods
Cultural controls, including the use of sticky materials are acceptable for use in organically managed citrus groves.

Monitoring and Treatment Decisions
Monitor the orchard in spring when honeydew-producing insects, such as aphids, appear. Check the abdomen of ants descending the tree trunks to see if they are swollen and translucent; this identifies them as honeydew-collecting species. Periodically inspect for ants and bark damage under the trunk wraps of several young trees. For the most effective and economical ant control, treat when ants are active in spring following winter rains and again in late August.

Common name (trade name)		Amount to Use (type of coverage)	Minimum Days before Harvest+
A.	STICKY POLYBUTENE MATERIALS#
	(Tanglefoot)
	RANGE OF ACTIVITY: Narrow (trunk climbers)
	PERSISTENCE: Long
	COMMENTS: For use on all varieties. Use polybutene-based products only. Do not apply sticky materials directly on the trunk; use a 6- to 18-inch wrap under the sticky material to protect the tree from sunburn. Exercise caution in applying multiple applications (more than 3 or 4)-watch for symptoms of bark cracking. Apply the sticky band high enough to avoid sprinklers, dust, and direct sunlight. Reactivate periodically by rubbing with a stick to remove dust. Check to ensure that hanging branches, sticks, weeds, etc. are not allowing ants access to trees.
B.	ABAMECTIN*
	(Clinch) 0.011%	1 lb/acre	12 hours
	RANGE OF ACTIVITY: Effective only against fire ants
	PERSISTENCE: Intermediate
	COMMENTS: A corn cob grit and soy oil bait. For use on all citrus varieties. Effective only against fire ants because they are attracted to the soy oil mixed with corn cob grits bait. Apply when fire ants are most active during the season (especially early summer and fall) and when they are most active during the day (early evening and early morning when soil temperature is above 60°F). Treatments are most effective if applied 2 days after an irrigation when ant activity is at a maximum. Do not irrigate again until at least 24 hours after application. Do not apply if rainfall is anticipated with 4-6 hours after application. Apply 1 lb Clinch/acre using properly calibrated ground equipment to assure proper dosage and uniform distribution. Retreatment may be desirable after 3-4 months.
C	PYRIPROXYFEN
	(Esteem Ant Bait) 0.5%	1.5-2 lb/acre	1
	RANGE OF ACTIVITY: Effective only against fire ants
	PERSISTENCE: Intermediate
	COMMENTS: A corn cob grit and soy oil bait. For use on all citrus varieties. Effective only against fire ants because they are attracted to the soy oil mixed with corn cob grits bait. Apply when fire ants are most active during the season (especially early summer and fall) and when they are most active during the day (early evening and early morning when soil temperature is above 60°F). Treatments are most effective if applied 2 days after an irrigation when ant activity is at a maximum. Do not irrigate again until at least 24 hours after application. Do not apply if rainfall is anticipated with 4-6 hours after application. Apply using properly calibrated ground equipment to assure proper dosage and uniform distribution. Retreatment may be desirable after 3-4 months.
D.	CHLORPYRIFOS
	(Lorsban) 4E*	1-3% solution (3-8 fl oz/gal water)	28
	RANGE OF ACTIVITY: Narrow as used for ant control.
	PERSISTENCE: Intermediate
	COMMENTS: For use on all varieties. Registered for ant control under a supplemental label. Apply when temperatures are warm and ants are most active. Apply by thoroughly spraying base of skirt-pruned tree trunks and ant nests on the ground. Repeat applications are needed; do not exceed 4 applications/year or 2.5 gal solution/acre.
	...OR...
	(Lorsban) 15G	6.7 lb/acre	28
	RANGE OF ACTIVITY: Narrow as used for ant control.
	PERSISTENCE: Intermediate
	COMMENTS: Apply with ground equipment to control foraging ants and suppress mounds. Do not apply where weed growth or other obstructions would impede uniform coverage of the orchard floor. Do not apply more than 67 lb/acre/crop season.

+	Minimum days before harvest takes into account the California restricted entry interval and the federal preharvest interval and lists the longer interval. (See Table 1 Mandatory Intervals Between Application, Reentry and Harvest, and Hazards to Bees.)
#	Acceptable for use on organically grown produce.
*	Permit required from county agricultural commissioner for purchase or use.

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 Co.
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura Co.
C. E. Kallsen, UC Cooperative Extension, Kern Co.
D. R. Haviland, UC Cooperative Extension, Kern Co.
Acknowledgments for contributions to the insect, mite, and snail section:
J. Barcinas, E. S. I., Corona, CA
R. Dunn, Badger Farming Co., 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

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