DISCOVERY, IDENTIFICATION AND RISK-ASSESSMENT OF BIOCONTROL AGENTS FOR SUPPRESSION OF SOUTH AMERICAN INVASIVE WEEDS AND INSECTS IN THE U.S.
Title: Acute exposure to low dose radiation disrupts reproduction and shortens survival of Wasmannia auropunctata (Hymenoptera Formicidae)queens
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2012
Publication Date: June 1, 2012
Citation: Calcaterra, L., Coulin, C., Briano, J., Follett, P.A. 2012. Acute exposure to low dose radiation disrupts reproduction and shortens survival of Wasmannia auropunctata (Hymenoptera Formicidae)queens. Journal of Economic Entomology. 105(3):817-822.
Interpretive Summary: Radiation is used as a postharvest treatment to disinfest fresh agricultural commodities of quarantine pests. The objective is to prevent reproduction and thereby prevent the insect’s introduction and establishment into new areas. Hawaii is currently exporting approximately 15 million pounds of fresh fruits and vegetables annually using irradiation to control fruit flies and other regulated pests. The presence of hitchhiking ants on exported products can cause rejection and return shipment to Hawaii. Ants are particularly problematic on exported rambutan and longan, but may be present on other commodities as well. The little fire ant is an invasive ant presumably originating from tropical South American forests that has spread throughout tropical and subtropical zones of the world, particularly in the Pacific. It was first reported in Hawaii in 1999, and has rapidly spread to a variety of agricultural sites such as nurseries, pastures, and orchards. We studied its tolerance to radiation to determine the dose sufficient for its control. This information may give us an idea of how tolerant ants in general are to irradiation. This study revealed that low radiation doses stopped reproduction in the little fire ant queens and should be sufficient as a sanitary treatment.
Irradiation is a postharvest quarantine treatment option to control ants and other hitchhiker pests on fresh horticultural products exported from Hawaii. The radiotolerance of the invasive little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae: Myrmicinae), was studied to determine a dose sufficient for its control. Queens from each of five laboratory micro-colonies started from five geographic locations in Argentina were irradiated at 20, 50, 70, or 100 Gy or left untreated as controls, and then followed for 13 weeks to observe colony growth. In general, queen survivorship, and the number of eggs, larvae, and pupae observed in the micro-colonies decreased with increasing irradiation dose. In the 50, 70, and 100 Gy treatments, the number of eggs observed was reduced by 68, 66, and d 76%, respectively, compared to untreated control colonies, the number of larvae in the 50, 70 and, 100 Gy treatments was reduced by 99.6%, and only one pupa was observed in the 50 Gy treatment and none in the 70 and 100 Gy treatments. Queens in the 100 Gy treatment had significantly reduced longevity compared with queens in the other treatments. Radiation doses >70 Gy stopped reproduction in W. auropunctata queens and should be sufficient as a phytosanitary treatment. Information from additional ants in other subfamilies is needed before recommending a generic irradiation treatment for ants.