Effect of low temperature between fractionated-dose irradiation doses on mating of the West Indian sweetpotato weevil, Euscepes postfasciatus (Coleoptera: Curculionidae)

Abstract

The effectiveness of the sterile insect technique (SIT) depends on the ability of released sterile males to mate with and inseminate wild females, but the use of gamma radiation to induce sterility negatively affects both somatic and reproductive cells of the sterilized insects. Recently, the effectiveness of fractionated-dose irradiation (FI), in which a sterilizing dose is delivered over time in a series of small irradiations, has been demonstrated in the West Indian sweetpotato weevil Euscepes postfasciatus (Fairmaire). FI improves male mating propensity compared with acute irradiation; however, this renewed technique takes a long time (72 h in the present circumstances) compared with the traditional technique (approximately 20 min) using single-dose irradiation (150 Gy) to fully sterilize this weevil. The extra time required by FI might negatively affect the quality of released sterile males, because weevils expend limited resources, such as metabolic energy or sperm, in mating freely in this period. We evaluated whether the temporal storage of weevils at low temperature (5°C and 15°C) improves the quality of sterile males compared with the normal condition (25°C). Temporal storage at low temperature in FI improves male mating propensity. For example, the sexually active phase of males exposed to 15°C was 18 days at least after irradiation. This period was longer than that of normal males (14 days). Meanwhile, this manner delayed male reproductive development and temporarily reduced mating competitiveness ability. If considering the long active phase of sterile males exposed to 15°C, these disadvantage would be cancelled out. We discuss the advantage of FI with temporal storage at low temperature in the eradication program using SIT for E. postfasciatus.

Reduced dispersal and survival in the sweet potato weevil (Euscepes postfasciatus) after irradiation

“…In the laboratory, irradiated weevils of E . postfasciatus are as active as normal weevils over the first 16 days after irradiation (Kumano et al , , ). Kinjo et al () estimated the survival of irradiated weevils at 90% or more in the field for 1 week and reported that 80% of the weevils may have survived for a further 2 weeks.…”

When a male perceives a female: the effect of waxy components on the body surface on decision-making in the invasive pest weevil

“…3 cm diameter, 1 cm thickness) to prevent interference and casual mating. Newly collected weevils were designated a substantial age of 0-day-old [34]. We used sexually matured 12- to 17-day-old virgin weevils for subsequent behavioural studies.…”