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How to Manage Pests
UC Pest Management Guidelines
Walnut
Southern Fire Ant
Scientific Name: Solenopsis xyloni
(Reviewed 12/07,
updated 12/07)
In this Guideline:
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The southern fire ant is 0.07 to 0.25 inch (1.7–6 mm) long,
has an amber head and thorax with a black abdomen. It has a painful sting that
causes visible swelling. Ant hills often appear as small mounds or
patches of loose soil. Fire ants vigorously swarm from the nest entrance when
disturbed; nondamaging species do not. Nests in orchards with low-volume irrigation
tend to be located around the edges of the wetted areas. In flood-irrigated orchards
with heavy soils, nests tend to be concentrated on the berms. Where lighter
soils are present, nests are located both on the berms and in the middles. Frequently,
southern fire ants nests are associated with clumps of weeds, such as nutsedge or spotted spurge.
Activity of these ant pests peaks in the morning and again just before sunset.
Do not confuse southern fire ant with the pyramid ant,
which is a beneficial species that is similar in size but active during mid-day
and found in sandy, weed-free areas. The pyramid ant does not swarm.
The southern fire ant has a wider distribution
and generally causes more damage than the pavement ant. Ants are more prevalent in drip- or sprinkler-irrigated
orchards than flood irrigated orchards. Ants feed on other hosts and are principally
a problem after walnuts are on the ground; nut damage increases in relation to
the length of time they are on the ground. They enter nuts through the soft
tissue at the stem end or through a codling moth injury.
If prolonged nut drop occurs and ants have been a problem in the
past, a bait application may be needed in August.
Treatment
Note: For instructions on constructing an EPA-approved bait
station, see the online version of this guideline.
| Common name |
Amount to Use** |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
(conc.) |
(dilute) |
(hours) |
(days) |
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| When choosing a pesticide, consider
information relating to impact on natural enemies
and honey bees and environmental
impact.
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| NOTE: Baits must be used in an EPA-approved bait station. |
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| A. |
S-METHOPRENE |
Label rates |
4 |
0 |
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(Tango) |
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UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471
Insects and Mites
C. Pickel, UC IPM Program/UC Cooperative Extension, Sutter/Yuba counties
W. J. Bentley, UC IPM Program/Kearney Agricultural Center, Parlier
J. A. Grant, UC Cooperative Extension, San Joaquin Co.
J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
W. W. Coates, UC Cooperative Extension, San Benito Co.
R. A. Van Steenwyk, Insect Biology, UC Berkeley
Acknowledgment for contributions to the insects and mites section:
W. H. Olson, UC Cooperative Extension, Butte Co.
L. C. Hendricks, UC Cooperative Extension, Merced Co.
G. S. Sibbett, UC Cooperative Extension, Tulare Co.
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