EARTH.COM - In many California citrus groves, the most troublesome ant is barely a tenth of an inch long. The Argentine ant does not feed on the trees, but it protects the insects that do.
These invasive ants feed on honeydew, the sugary liquid excreted by sap-sucking pests such as mealybugs, scale insects and psyllids.
In exchange, the ants guard those pests against the parasitic wasps and predators that would normally keep them in check.
Across coastal California, that partnership has turned one small ant into a major obstacle for growers who rely on natural enemies to control pests in orchards and vineyards.
An invader from South America
The Argentine ant, Linepithema humile, is native to the Paraná River basin in Argentina, Brazil, Paraguay and Uruguay. It was first detected in the United States in Louisiana in 1891, likely arriving with shipments of coffee from Brazil.
The first California population was found in 1905 in Ontario, in San Bernardino County, according to the University of California, Riverside biological control lab led by entomologist Mark Hoddle.