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By Sandra Avant
April 11, 2014
U.S. Department of Agriculture (USDA) scientists are developing innovative techniques to combat one of the world's worst invasive species, the red imported fire ant.
In the United States, fire ants cost $7 billion in control, damage repair and medical care each year. They infest millions of acres in urban, agricultural, wildlife, recreational and industrial areas.
Scientists at the Agricultural Research Service (ARS) Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Fla., are investigating chemicals called pheromones that are secreted by the ants. Pheromones signal alarm, mark trails to food, attract workers to brood and the queen, and unite males and females for mating.
Entomologist Man-Yeon Choi and chemist Robert Vander Meer at the Gainesville center have shown for the first time that a neuropeptide called pheromone biosysnthesis activating neuropeptide (PBAN) activates production of trail pheromones in ants.
PBAN was first discovered by ARS scientists in Beltsville, Md., in the 1980s. They found that the hormone regulates sex pheromone production in female moths. Since then, scientists have found that other insects, including cockroaches, have this type of PBAN family peptides made of two or more amino acids.
Choi injected fire ant workers with PBAN peptides and found a significant increase in pheromone production. He and Vander Meer also identified the DNA sequence of both the PBAN gene and receptor gene, which allowed them to test the function of PBAN in trail pheromone production using a new technique called RNA interference (RNAi). This involves taking normally single-stranded RNA from a gene and making double-stranded RNA (dsRNA) that can be used to suppress that gene's expression.
When scientists injected dsRNA of either the PBAN gene or receptor gene into ants, they found that ants produced less trail pheromone. They also discovered that adult ants and larvae injected with PBAN-RNAi had significant mortality, compared to ants that didn't receive the injection. Pupae that received the treatment had delayed development and a high death rate.
Scientists plan to investigate whether other pheromones are activated by PBAN, and if dsRNA can be used for fire ant control.
ARS is USDA's principal intramural scientific research agency.
Read more about this research in the April 2014 issue of Agricultural Research magazine.