2012 Annual Report
1a.Objectives (from AD-416):
1. Identification of specific proteins that can be used to discern fire ants from other ant species.
2. Define attractant characteristics of fire ant alarm pheromone.
3. Characterize environmental conditions in cargo containers and conduct initial probes of the use of the attractant to trap fire ants in cargo containers.
1b.Approach (from AD-416):
Obj. 1 - Much of the first year will be devoted to identifying specific proteins that can be used to discern fire ants from other ant species. Initially, experiments will be conducted on poison sac proteins; these tend to be unique even among congeners. Genes corresponding to certain poison sac proteins (e.g. SolI) and their homologues from other ant species will be sequenced, translated and compared. Those with sufficient differences will be marked as candidates for the next step.
Obj. 2 - Bioactive release rates for the fire ant alarm pheromone will be determined through a combination of bioassays and chemical analyses.
Obj. 3 - A cargo container will be rented and placed on location. Environmental measurement equipment will be used to assess daily fluctuations in, e.g.
temperature and humidity. Fire ant colonies will be placed in cargo containers and initial trap prototypes evaluated.
These results directly support and correspond to inhouse project objective 3: Characterize semiochemicals through investigation of pheromone biosynthesis and release; use these findings to develop novel biologically-based control and surveillance methods, including the detection and treatment of incipient or low level populations.
A lateral flow immunoassay (LFIA) for rapid, field detection of fire ants has proceeded. By law, regulatory personnel in the United States must prohibit movement of any fire ant-contaminated shipping commerce from entering non-quarantined areas. Unfortunately, cargo must be held until positive identification of the ant samples in the cargo is made. The current identification process requires extensive training of personnel and can delay movement of cargo by days. The LFIA accelerates the identification process at interception points such as quarantined boundaries and ports. The kit is easy to use and requires no previous training to make a positive identification for fire ants. The sample size is small, requiring one to five ant workers. The LFIA is based on immunological/nanoparticle detection of Solenopsis invicta venom protein II. Monoclonal antibodies were designed to unique areas of this protein. One monoclonal antibody is conjugated to gold particles and serves as the detection antibody while the second monoclonal antibody serves as the capture antibody. From the moment a fire ant sample is collected, the assay may be completed in 5 to 10 minutes. The impact of this invention on agriculture is significant because it will limit the spread of fire ants into non-quarantined areas by providing a rapid, definitive test for use by regulatory personnel. Fire ants are an invasive species that cost U.S. citizens at least 6 billion dollars annually. Indeed, the invention has potential worldwide application to facilitate interception of fire ants at ports of entry.
Significant progress was also made in developing a prototype surveillance system which has been constructed and evaluated. The system consists of a location for release of a fire ant specific pheromone that attracts worker ants up ramps that channel the ants into a position where photographs are taken every 30 seconds. The photos are stored in memory and downloaded when convenient via a USB connection. The next iteration will incorporate an ant sensor so that the photos will only be taken when an object is detected within view of the camera. This system will have broad applicability to detection of invasive pests in general.
Research progress was monitored by e-mail and telephone correspondence between the ARS scientist and APHIS.