Phytosanitary irradiation of Liriomyza trifolii (Diptera: Agromyzidae)

Authors: Hallman, Guy; GUO, KUN - Chinese Academy Of Medical Sciences; LIU, TONG-XIAN - Northwest Agricultural & Forestry University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2011
Publication Date: 12/18/2011
Citation: Hallman, G.J., Guo, K., Liu, T. 2011. Phytosanitary irradiation of Liriomyza trifolii (Diptera: Agromyzidae). Journal of Economic Entomology. 104:1851-1855.

Interpretive Summary: Leafminers of the insect family Agromyzidae are pests of many vegetables, flowers and ornamental foliage. Methyl bromide fumigation is often used as a phytosanitary treatment when quarantined leafminers are found in shipped commodities. Alternatives are sought because methyl bromide is an ozone-depleting substance that is being phased out of use. Ionizing radiation is a safe alternative that is increasing in use worldwide. A radiation dose of 400 gray is accepted by the USDA for all insects (except pupae and adults of the butterfly and moth order, Lepidoptera) on all commodities. Efforts to lower this dose and make it acceptable to other countries involve determining doses required to control major quarantine pest groups. Leafminers are one such group for which no useful information on dose required to control the pests exists. This research sought the dose required to control a major leafminer pest, Liriomyza trifolii. It was collected on cotton and bell pepper in the Weslaco, TX area and reared on green beans and bell peppers before being irradiated in the late puparial stage (the quiescent stage before the adult emerges). Leafminers collected from cotton and reared on green beans were more tolerant than those collected and reared on bell pepper. A dose of 203 Gy may control the leafminer. This research introduced a variation of statistical analysis that may be useful in phytosanitary irradiation research where the measure of control often involves a response not from the generation being irradiated but from the next generation.

Technical Abstract: Agromyzid leafminers are economic and quarantine pests of a variety of vegetables, flowers and ornamental foliage. Methyl bromide fumigation is often used as a phytosanitary treatment when quarantined agromyzids are found in shipped commodities; alternative treatments are sought. Ionizing radiation is a viable alternative that is increasing in worldwide use. A dose of 400 Gy is accepted by APHIS, USDA for all insects (except Lepidoptera pupae and adults) on all commodities. Efforts to lower this dose and make it acceptable to other countries involve determining radiotolerance of representatives from major quarantine pest families. Agromyzidae is one such family for which no useful information on radiotolerance exists. This research sought the dose required to control a major agromyzid pest, Liriomyza trifolii (Burgess). It was collected on Gossypium hirsutum L. and Capsicum annuum L. in the Weslaco, TX area and reared on Phaseolus vulgaris L. and C. annuum, respectively, before being irradiated in the late puparial stage. The measure of efficacy was prevention of F(1) mine formation. Puparia collected from G. Hirsutum and reared on P. vulgaris were more radiotolerant than those collected and reared on C. annuum. A dose of 203 Gy may prevent F(1) mine formation of L. trifolii. This research introduced a variation of probit analysis where the direct response of the treated individual is not measured, but the response of the F(1) generation is. This type of analysis is useful in phytosanitary irradiation research where the measure of efficacy often involves a response of the F(1) generation.