Postharvest phytosanitary disinfestation of Thaumatotibia leucotreta (Lepidoptera: Tortricidae) in citrus fruit: Validation of an ionizing radiation treatment
Keywords:
false codling moth, authentication, γ-radiation, probit-9, target doseAbstract
The probit-9 level efficacy of 100 Gy ionizing radiation was evaluated as a postharvest phytosanitary treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). Earlier work had identified the 5th instar as the most radiotolerant life stage, and that reproduction of moths from these larvae reared in artificial medium was significantly greater than that of moths from feral larvae in citrus fruit. A total of 124,493 fifth instars reared in artificial media were treated with a target dose of 100 Gy (100 ± 8.5%) of ionizing radiation. The treatment reduced the subsequent mean numbers of pupae and moths by 49.4% and 85.6%, respectively, relative to the control. The gender ratio of the moths developing from treated larvae was predominantly male with a female to male ratio of 1:2.4, compared with the untreated control ratio of 1:0.8. None of the moths was able to fly, and mating was reduced by 83.3%. The moths were totally infertile as no eggs were deposited. These results successfully validate the probit-9 level efficacy of 100 Gy of ionizing radiation for phytosanitary treatment.
Resumen
La eficacia de nivel probit-9 de radiación ionizante de 100 Gy fue evaluada como tratamiento fitosanitario poscosecha para Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). Trabajos anteriores habían identificado el quinto estadio como el estadio de vida más radiotolerante, a su vez la reproducción de las polillas que se desarrollaron de estas larvas criadas en medio artificial fue significativamente mayor que la de las polillas de larvas salvajes sobre los cítricos. Un total de 124.493 larvas del quinto estadio criadas en un medio artificial fueron tratadas con una dosis objetiva de 100 Gy (100 ± 8.5%) de radiación ionizante. El tratamiento redujo el promedio del número de pupas y polillas subsiguientes por 49,4% y 85,6%, respectivamente, en relación con el control. La proporción de los sexos de las polillas que se desarrollaron de las larvas tratadas fue predominantemente masculino con una radio de macho a hembra de 1:2,4 en comparación con el radio de control (no tratado) de 1:0,8. Ninguna de las polillas fue capaz de volar, y el apareamiento se redujo en un 83,3%. Las polillas fueron totalmente infértiles y no se depositaron huevos. Estos resultados validan con éxito la eficacia de nivel probit-9 de 100 Gy de radiación ionizante para tratamiento fitosanitario.
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