Sexual Competitiveness, Field Survival, and Dispersal of Anastrepha obliqua (Diptera: Tephritidae) Fruit Flies Irradiated at Different Doses

Abstract

The sterile insect technique (SIT) is used in area-wide pest management programs for establishing low pest prevalence and/or areas free of fruit flies (Diptera: Tephritidae). The aim of this technique is to induce high levels of sterility in the wild population, for this the released insects must have a high sexual competitiveness and field dispersal. However, radiation decreases these biological attributes that do not allow it to compete successfully with wild insects. In this study the sexual competitiveness, field survival and dispersal of Anastrepha obliqua (Macquart; Diptera: Tephritidae) irradiated at 0, 40, 50, 60, 70, and 80 Gy were evaluated in laboratory. A dose of 60 Gy produced 98% sterility, whereas doses of 70 and 80 Gy produced 99% sterility. Sexual competitiveness was assessed in field cages, comparing males irradiated at 0, 50, 60, 70, and 80 Gy against wild males for mating with wild fertile females. Males irradiated at 50 and 60 Gy achieved more matings than those irradiated at 70 and 80 Gy. Wild males were more competitive than mass-reared males, even when these were not irradiated (0 Gy). There was no effect of irradiation on mating latency, yet wild males showed significantly shorter mating latency than mass-reared males. Female remating did not differ among those that mated with wild males and those that mated with males irradiated with different doses. The relative sterility index (RSI) increased from 0.25 at 80 Gy to 0.37 at 60 Gy. The Fried competitiveness index was 0.69 for males irradiated at 70 Gy and 0.57 for those irradiated at 80 Gy, which indicates that a 10 Gy reduction in the irradiation dose produces greater induction of sterility in the wild population. There were no significant differences in field survival and dispersal between flies irradiated at 70 or 80 Gy. Reducing the irradiation dose to 60 or 70 Gy could improve the performance of sterile males and the effectiveness of the SIT. Our results also distinguish between the effects of irradiation and mass-rearing on the performance of sterile males.

Sexual competitiveness of fertile and sterile, wild and mass‐reared males of Anastrepha obliqua

“…Compared to the effects of irradiation, the effects of mass-rearing can be as damaging to male sexual behavior (Cayol, 2000). Here, however, and contrary to previous studies (Rull et al, 2012;Gallardo-Ortiz et al, 2018), we found no effect of mass-rearing on male mating frequency. That is, there was no significant difference in mating rate between fertile mass-reared vs. wild males.…”

“…Toledo et al (2004) suggested reducing the irradiation dose in A. obliqua from 80 to 60 Gy, to reach a better balance between levels of sterility and sexual competitiveness in the sterile males. In a recent study on this species, we found that males irradiated at 60 Gy had higher survival in the field estimated through recaptured flies, achived more matings, induced higher levels of sterility into the wild population than those irradiated at 80 Gy (Gallardo-Ortiz et al, 2018). Thus, results here also support lowering the irradiation dose of A. obliqua.…”

“…Irradiation probably caused an additional stress to wild males. In a recent study on this species, we found that males irradiated at 60 Gy had higher survival in the field estimated through recaptured flies, achived more matings, induced higher levels of sterility into the wild population than those irradiated at 80 Gy (Gallardo-Ortiz et al, 2018). susceptible to the effects of irradiation (Liedo & Carey, 1996).…”

Overexpression of an antioxidant enzyme improves male mating performance after stress in a lek-mating fruit fly

“…[20,[22][23][24]). The radiation used for sterilization in SIT causes oxidative stress that reduces the mating competitiveness and lifespan of sterilized males, thereby hindering the performance of these biological control agents and increasing economic costs associated with SIT [20,[25][26][27][28]. Numerous transgenic strategies have been developed to improve SIT, for example, conditional lethality strains that obviate the need for radiation sterilization and genetic sexing strains that eliminate unwanted females [29,30].…”

Quality control and characterization of the testicles and ovaries of irradiated Anastrepha obliqua from Brazil

“…Since 1997, for example, the FAO/IAEA/USDA has provided a set of standards for assessing the quality of sterile fruit flies used in SIT programs (FAO, 2003). Studies of radiosterilization in A. obliqua assessing biological parameters are very scarce, and have been carried out mainly on Mexican strains (Gallardo-Ortiz et. al., 2018;Orozco-Dávila et al, 2017;Rull et al, 2012;Toledo et al, 1993Toledo et al, , 2004.…”