Agriculture: Citrus Pest Management Guidelines


  • Argentine ant: Linepithema humile
  • Native gray ant: Formica aerata
  • Red imported fire ant: Solenopsis invicta
  • Southern fire ant: Solenopsis xyloni
  • Description of the Pest

    (View Ant Identification Key) (PDF)

    There are numerous species of ants present in citrus orchards, however, the most common are the Argentine ant (Southern and Coastal California), the native gray ant (San Joaquin Valley) and the southern fire ant (statewide). The red imported fire ant has been found in Southern California, but is not yet established in citrus orchards. It is important to identify the primary ant species in the orchard, because management tactics depend on which ant species is present.

    The Argentine ant is a small, uniformly deep brown ant. Worker ants travel in characteristic trails on trees, the ground, or irrigation lines and build their nests underground. Ant numbers peak in mid-summer through early fall.

    The southern fire ant is light reddish brown with a black hairy abdomen. They usually swarm in late spring or early summer. These ants build nests of loose mounds or craters near bases of trees, do not aggregate in colonies as large as those of the Argentine ant, and will bite and sting.

    Native gray ants are gray and considerably larger than the other two species. They nest in topsoil or under rocks and debris and move in irregular patterns. In contrast to Argentine and fire ants, the native gray ant is solitary and its importance in disrupting biological control is often underestimated.

    Red imported fire ant is new to California and can make large, dome-shaped mounds. They feed on almost any plant or animal material, and they bite and sting.


    Most ant species feed on honeydew excreted by various soft scales, mealybugs, cottony cushion scales, whiteflies, psyllids, and aphids. As part of this relationship, they protect these pest insects from their natural enemies, thus interrupting biological control. They also protect some non-honeydew-producing pests, such as California red scales.

    Argentine and native gray ants are the most common ant species that aggressively protect citrus insect pests. In addition, Argentine ants and fire ants can plug up irrigation sprinklers. Fire ants directly damage citrus by feeding on flowers and damaging young, developing fruit. They chew on the bark and cambium of young trees to feed on sap; this can girdle and kill young newly planted trees. They also sting people working in the orchard and may cause allergic reactions.


    Ants can be extremely disruptive to an IPM program. The Argentine, native gray, and fire ants can be prevented from climbing trees by skirt pruning and the use of sticky materials applied on top of a tree wrap to the bark as well as with insecticides.

    Biological Control

    No effective natural enemies of the ants 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, as oil-based materials may cause phytotoxicity and should not be used.

    The application of sticky polybutene materials directly to the trunk of citrus trees can cause bark cracking, especially if multiple applications are applied to the same area of the trunk, the area is exposed to sunlight (topworked trees), or both. The sticky material can be applied on top of a tree wrap, but this is both laborious and expensive. Young trees, which have a very thin cambium layer, are most susceptible to damage.
    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. Apply it high above the ground, just below the crotch of the tree, to increase the persistence of sticky material, to reduce dust and dirt contamination, and to decrease irrigation wash-off.

    To prevent bark damage by 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 young trees. When trees are large enough, remove the trunk wraps, which provide protection for ants.
    Ants are attracted to trunk gumming. If gum is observed, inspect and if necessary, treat for Phytophthora gummosis (see Disease section). Bordeaux whitewash helps prevent gumming.

    Cultivation reduces ant numbers but may create so much dust that it disrupts biological control of other pests.

    Organically Acceptable Methods

    Use cultural controls, such as banding trunks with sticky materials in combination with skirt pruning to reduce access points, in organically managed citrus groves. Boric acid is approved for ant control in organic citrus. It is used in liquid bait stations which must be refilled frequently to prevent evaporation from concentrating the pesticide making it unattractive to ants.

    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 young trees.


    Baits are the preferred chemical method for ant control whenever feasible. Effective bait insecticides have slow-acting toxicants that worker ants collect and feed to other ants, including nest-building immatures and queens. For the most effective and economical ant control, apply insecticides in early summer when ant numbers are just beginning to increase and are becoming active on the ground surface. To determine which bait to use, identify your primary ant species; fire ants are predominantly protein feeders (preferring oil-based baits) whereas most gray and black ants are sugar feeders (preferring liquid sugar baits).

    Corncob Grit and Oil Baits

    Solid baits utilize treated corncob grits mixed with soybean oil as the food attractant plus an insecticide. These are effective for the primarily protein-feeding fire ants. The toxicants tend to degrade in light, so apply baits early in the morning or late in the day when ants are most active and will rapidly take the bait into the nest. Generally, corncob grit type baits are broadcast over the acreage that needs to be treated. However, spot application of baits at the location of the ant nest is preferred over widely spreading the bait because it concentrates the food where the ants are.

    Sugar-water-based Baits

    Liquid baits use a toxicant mixed in sugar water, which disguises the toxicant as well as helps attract the ants. These baits are most useful for the liquid sugar-feeding Argentine and native gray ants. Evaporation of water can cause the concentration of the toxicant to increase to a level in the bait that becomes repellant to ants. All liquid baits must be used in an EPA-approved bait station. Currently, boric acid is the only product that is registered that has been proven to fully control ants in citrus orchards.

    Broad-spectrum Insecticide Sprays

    The alternative to liquid sugar-bait stations or corncob grit baits is to use a broad-spectrum insecticide sprayed at the trunk and soil interface or inside the wraps of young trees. It is quicker acting than a bait, but not as long-lasting because the residue breaks down quickly. In addition, sprays kill only the worker ants on the soil surface, while baits are carried into the mound and fed to other ant stages.

    Common name Amount to use REI‡ PHI‡
    (Example trade name) (type of coverage)** (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
      (Tanglefoot)   NA NA
      RANGE OF ACTIVITY: Pests: narrow (trunk climbers); Natural enemies: few, if any
      PERSISTENCE: Pests: long; Natural enemies: 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.
    A corncob 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 corncob 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 to 6 hours after application. While these baits can be broadcast using properly calibrated ground equipment to assure proper dosage and uniform distribution, spot applications at the location of the ant nest are preferred. Retreatment may be desirable after 3 to 4 months.
      (Clinch bait 0.011%) 1 lb/acre 12 0
      RANGE OF ACTIVITY: Pests: narrow (fire ants); Natural enemies: other ants
      PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
      (Esteem Ant Bait 0.5%) 1.5–2 lb/acre 12 1
      RANGE OF ACTIVITY: Pests: narrow (fire ants); Natural enemies: other ants
      PERSISTENCE: Pests: intermediate; Natural enemies: none
      COMMENTS: This insecticide takes several weeks to begin to kill the colony because it is an insect growth regulator. It does not kill the workers, but instead stops the growth of the immature ants and breaks the reproductive life cycle of the queen. This causes colony death as the worker ants age and die and are not replaced.
      (Altrevin Fire Ant Bait) 1.5 lbs/acre 12 5
      RANGE OF ACTIVITY: Pests: narrow (fire ants); Natural enemies: other ants
      PERSISTENCE: Pests: intermediate; Natural enemies: none
    Evaporation of water can cause the concentration of the toxicant to increase to a level in the bait that becomes repellant to ants. All liquid baits must be used in EPA-approved bait stations.
    A. Boric Acid
      (Gourmet Liquid Ant Bait)# Label rates NA 0
      RANGE OF ACTIVITY: Pests: All ants; Natural enemies: None
      PERSISTENCE: Pests: Short; Natural enemies: None
      COMMENTS: In organically grown fruit, may be used under a Special Local Need (SLN) registration. For use against honeydew-feeding ant species, including Argentine ant and native gray ant.
    Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
    # Acceptable for use on organically grown produce.
    * Permit required from county agricultural commissioner for purchase or use.
    1 Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).
    NA Not applicable.
    Text Updated: 07/23
    Treatment Table Updated: 07/23