How to Manage Pests

UC Pest Management Guidelines

Grape

Ants

Scientific names:
Argentine ant: Linepithema humile
Gray ant: Formica aerata and Formica perpilosa
Pavement ant: Tetramorium caespitum
Southern fire ant: Solenopsis xyloni
Thief ant: Solenopsis molesta

(Reviewed 6/06, updated 10/08)

In this Guideline:


DESCRIPTION OF THE PESTS   (household ant key)

The most prevalent of the ant species in vineyards, the Argentine ant, is about 0.13 inch (3 mm) long, uniformly deep brown to light black and does not bite or sting. The Argentine ant has one petiole node (hump) between the thorax and the gastor (swollen part of abdomen right behind the petiole). Worker ants travel in characteristic trails on vines, trellis wires, the ground, and drip irrigation laterals. They forage during all daylight hours. Ant populations peak in midsummer and early fall. Their nests are very shallow, usually within 2 inches of the soil surface.

The pavement ant is 0.13 inch (2–3 mm) long and has a dull, blackish brown body that is covered with coarse hairs. The head and thorax have many parallel furrows. Pavement ants have two nodes between the thorax and the gastor. They move in slow deliberate motion. They prefer to nest in sandy or loam soils.

The southern fire ant, also called the California or native fire ant, is light reddish brown with a black abdomen. The entire body is covered with golden hairs and has two nodes between the thorax and the gastor. Workers range in size from 0.1 to 0.018 inch (2.5–4.5 mm ). They do not usually travel in conspicuous trails and will swarm over the ground when disturbed. This ant will sting when provoked. Southern fire ants build nests of loose mounds or craters near bases of vines around wetted areas and do not aggregate in colonies as large as those of the Argentine ant. They forage in the morning and early evening and are underground during hot periods.

Native gray ants, also called field ants, are larger than the other ants, measuring up to 0.3 inch (7.5 mm) and, like the Argentine ant, have one petiole node (hump). These gray ants nest in topsoil or under rocks and debris, move in an irregular jerky manner, and generally do not travel in trails or sting. Formica aerata is more common in the San Joaquin Valley whereas Formica perpilosa occurs primarily in the Coachella Valley. Native gray ants do not trail and appear solitary.

Thief ants are extremely small ants (1–1.5 mm) with yellowish, shiny bodies. They are pests of grapes primarily in the Coachella Valley.

An illustrated key that covers common ant species (except gray ants) may be of value when identifying ants in vineyards.

DAMAGE

Ants can be extremely disruptive to IPM programs, especially Argentine and native gray ants. These ants feed on honeydew excreted by the European fruit lecanium scale and mealybugs. As part of this relationship, they also protect these honeydew-producing insects from predators and parasites, thus disrupting biological control.

MANAGEMENT

Ants may be more of a problem in vineyards with cover crops; the exception appears to be a vetch cover crop, because it supplies ants with adequate amounts of nectar and keeps them from moving into vines. Manage ants when they are interfering with biological control of pests. Cultural practices and sprays can be used in an integrated program.

Cultural Control

Tilling the soil for weed control will also disturb the nesting sites of ants and help to reduce their populations. Use of a French plow in the vine row will disrupt ant colonies.

Planting a cover crop of common vetch (Vicia sativa) can help to keep gray field ants (Formica sp.) off the vines. Common vetch has an abundance of nectaries that attract the ants away from the honeydew-producing insects. In studies it was planted in a 80:20 mixture with 20% Merced rye so that it could establish in late fall and winter in order to attract the ants during spring and early summer. The addition of rye to the mixture helps to provide structure and support in the cover crop for the vetch. A heavy seeding rate (120 lb/acre) helps to ensure a good stand. The effect of other nectary-bearing cover crops on attracting ants has not been evaluated. (Research using cover crops to attract Argentine ants, Linepithema humile, has not been conducted.)

Organically Acceptable Methods

Organically acceptable management tools are the cultural controls.

Monitoring and Treatment Decisions

Monitor the vineyard in spring when honeydew-producing insects such as scale and mealybugs appear as outlined in DELAYED-DORMANT AND BUDBREAK MONITORING (wine/raisin grapes or table grapes) and record observations on a monitoring form (example formPDF). Check the abdomen of ants descending the trunks to see if they are swollen and translucent; this helps identify them as honeydew-collecting species. Periodically inspect for ants on arms, cordons, and canes.

Insecticides

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 immatues and queens. For the most effective and economical ant control, treat when ants are active in early spring following winter rains and again in late August.

To determine which bait to use, identify your primary ant species; fire ants are predominantly protein feeders whereas most gray and black ants are sugar feeders.

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 int he morning or late int he day when ants are active and will 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 toxicants as well as helps attract the ants. These baits are most useful for the liquid sugar-feeding Argentine and native gray ants. Evaporation of the bait 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.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to impact on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
LIQUID BAITS (Must be used in approved bait station such as KM Ant Pro or constructed from an approved design [available online])
 
A. S-METHOPRENE
  (Tango)   4 0
  Pests: narrow (sugar-feeding ants); Natural enemies: none
  Pests: as long as the bait station is filled; Natural enemies: none
  MODE OF ACTION GROUP NUMBER1: 7A
 
B. IMIDACLOPRID›
  (Vitis Liquid Ant Bait)   0 0
  Pests: narrow (sugar-feeding ants); Natural enemies: none
  Pests: as long as the bait station is filled; Natural enemies: none
  MODE OF ACTION GROUP NUMBER1: 4A
 
SOLID BAITS
 
A. ABAMECTIN*
  (Clinch bait) 0.011% 1 lb/acre 12 0
  Pests: narrow (fire ants); Natural enemies: other ants
  Pests: intermediate; Natural enemies: intermediate
  MODE OF ACTION GROUP NUMBER1: 6
  COMMENTS: 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 4–6 hours after application. While Clinch 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 3–4 months.
 
B. PYRIPROXYFEN
  (Esteem Ant Bait) 0.5% 1.5–2 lb/acre 12 1
  Pests: narrow (fire ants); Natural enemies: other ants
  Pests: intermediate; Natural enemies: none
  MODE OF ACTION GROUP NUMBER1: 7C
  COMMENTS: 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 4–6 hours after application. While this bait 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 3–4 months.
 
SPRAYS
 
A. CHLORPYRIFOS*
  (Lorsban) 4EC 1.5–2 pt 24 76
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Use allowed under a Special Local Need Registration. Chlorpyrifos may either be used for ant control or mealybug control, but not for both pests on the same grape crop. Spray to obtain thorough coverage of the base of each vine, the vine stakes, and the surrounding soil, out to about 1 ft from the base of the vine. Running a blade ahead of the sprayer to disturb the soil may increase contact of the material. Do not apply to foliage or fruit. May be used at any time during the season, keeping in mind the 76-day preharvest interval, but do not exceed 3 applications/year. Avoid drift and runoff into surface waters. In addition to water quality concerns, the EC formulation of chlorpyrifos produces volatile organic compounds (VOCs), which are a major air quality issue.
 
** Apply with enough water to provide complete coverage.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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.
* 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 are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448

Insects and Mites

W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
F. G. Zalom, Entomology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
P. A. Phillips, UC IPM Program, Ventura County
D. R. Haviland, UC IPM Program, Kern County
K. M. Daane, Kearney Agricultural Research Center, Parlier
M. C. Battany, UC Cooperative Extension, San Luis Obispo County
Acknowledgment for contributions to Insects and Mites:
J. Granett, Entomology, UC Davis

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