Alkali bee-Pavement ant

Tetramorium caespitum

Pest description and damage Pavement ants (2-3 mm) are dark brown with paler legs and antennae. Ant nests can be found in exposed soils, under pavement or stones and in alkali bee beds. Ants will actively kill adult bees to get to and consume bee larvae and pollen from bee cells.

Management-chemical control

Pavement ant colonies or ant bed locations need to be identified and treated in order to remove pavement ant pests. Night time inspections will reveal more foraging ants. Follow trails to locate ant beds. Granules containing cypermethrin or bifenthrin are suggested for control treatments and may reduce risk of non-target exposure, however both are toxic to bees and should be used with caution. They are fast-acting contact insecticides that target foragers but not the colony and therefore may be ineffective long-term treatments. Baits with active ingredients propoxur or indoxacarb are also too fast-acting and are not effective controls. Protein baits containing hydramethylnon, fipronil, or boric acid (borate or various forms of sodium borate), and avermectin B (abamectin) are slow-acting and attractive to pavements ants making them more likely to be brought back to the colony and queen. Hydramethylnon is relatively non-toxic to bees; fipronil and boric acid are toxic and pose a high risk to bees. Use covered-bait stations to reduce exposure to bees and only when ants are present. Place baits in areas where ant activity has been observed or along ant trails. Applying late winter and early spring baits, when populations are growing, may be the most effective timing of treatments. Note that ant baits and treatment registrations change over time. Read and follow current label instructions for effective control.

For more information:

Rust, M.K. and D.H. Choe. 2012. Pest Notes: Ants. University of California Agriculture and Natural Resources Statewide Integrated Pest Management Program Publication (7411).