Assessment of quality of the sterile male insects that are being mass‐reared for release in area‐wide integrated pest management programmes that include a sterile insect technique component is crucial for the success of these programmes. Routine monitoring of sterile male quality needs to be carried out both in the mass‐rearing facility and in the field. Simple bioassays that can be conducted in the laboratory and that would be surrogates for laborious field tests would be a very cost‐effective way of monitoring sterile male field performance. Simple flight cylinders were used to assess whether these could detect differences in quality of male codling moth Cydia pomonella. The number of male and female codling moths that flew out of the cylinders was influenced by cylinder diameter, cylinder height and number of hours following the initiation of the test. The flight cylinder bioassay was capable of detecting differences in quality of codling moths induced by irradiation when moths were shipped, but no differences were found in flight ability when the moths were not transported. The tests also confirmed that handling and shipment reduced quality more for irradiated than for non‐treated codling moth, and that insect quality was significantly influenced by larval rearing protocols. The flight cylinder bioassay was therefore successful in detecting differences in codling moth quality induced by various treatments that had been identified previously by more complex laboratory bioassays and field trials. Treatment differences were most likely detected when flight cylinders were 16 cm high.

Codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is the key pest of pome fruit in South Africa, and it’s control in apple and pear orchards relies on the application of insecticides and pheromone‐mediated mating disruption. Development of resistance to insecticides and placement of restrictions on the use of certain insecticides has made control of codling moth in South Africa increasingly problematic. The use of the sterile insect technique (SIT) as a control tactic for codling moth is under investigation as a potential addition to the current control strategy. We investigated the radiosensitivity of a laboratory strain of codling moth that was established from moths collected from commercial and organic orchards in the Western Cape, South Africa. Fecundity and fertility of this strain following radiation were consistent with values for the codling moth strain in the Canadian rearing facility in British Columbia. For both strains, the female codling moth was considerably more radiosensitive than the male. At a radiation dose of 100 Gy or higher, treated females were 100% sterile. The fertility of the South African strain was higher (86.3%) than for the Canadian strain (71.9%). This difference in fertility between the two strains was maintained when the dose of radiation was 100 Gy. However, the level of fertility was very similar between the two strains for doses ≥150 Gy. Therefore, based upon previously published work and the data from this study, an operational dose of 150 Gy is recommended for future codling moth SIT programmes in South Africa.

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Maximum production and fitness of insect species that are mass‐reared for biological control programmes such as the sterile insect technique (SIT) have benefitted from the employment of quality control and quality management. With a growing interest in the use of SIT as a tactic for the suppression/eradication of key lepidopteran pests, such as the codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), there is a parallel interest in inexpensive bioassays that can accurately detect differences in insect quality and monitor insect field performance. In this study, we examined laboratory (mating and flight ability) bioassays and field (field cage and open field release) bioassays simultaneously to discern the ability of the different bioassays to predict quality and field performance of codling moths produced in a commercial mass‐rearing facility. Moth quality was degraded by different levels of radiation during the sterilization procedure. Both the laboratory flight bioassay and the field cage bioassay successfully detected quality and performance differences that were relevant to moth performance in the field. However, the study data suggest that the field cage bioassay was a better predictor of the daily performance of males that had been released in the orchard than the laboratory flight bioassay. Conversely, data suggest that the controlled climatic conditions of the laboratory allowed the flight cylinder bioassay to be more sensitive in detecting daily fluctuations in the quality of moths caused by factors within the mass‐rearing facility. Therefore, both laboratory and field bioassays may be required to provide feedback on quality and performance of mass‐reared moths in a SIT programme.

The sterile insect technique (SIT) has been successfully applied against codling moth Cydia pomonella (Linnaeus) (Lepidoptera; Tortricidae) in British Columbia since 1992 where the mass‐rearing facility produces between 15 and 16 million moths per week. Due to the seasonality of this pest, the facility is only fully utilized for part of the year. The time and expense of implementing SIT against codling moth in South Africa may be substantially reduced if moths from Canada were sexually compatible with those from South Africa. In addition, because the pome fruit‐growing season in both countries is opposite, the programme in Canada might benefit by maintaining moth production year‐round and selling moths to South Africa. Semi‐field studies in small cages and release‐recapture studies were conducted in an unsprayed apple orchard in South Africa to assess mating compatibility of laboratory‐reared codling moth from Canada and wild codling moths from South Africa. The results suggest that Canadian codling moth males were equally attracted to calling Canadian and South African females despite the fact that Canadian moths had been transported (from Canada to South Africa) for 48 h as both pupae and adults. The data also suggest that at lower field temperatures Canadian moths were more active than South African moths. Results from the release‐recapture field trials indicated that Canadian and South African males were equally attracted to Canadian and South African females. These results suggest that codling moths from Canada and South Africa are fully compatible and indicate that Canadian moths can be used for SIT studies in South Africa. As these studies were conducted with moths from two very different climatic and time zones, it is proposed that populations of codling moth in other pome fruit production areas may also be compatible with the Canadian moths.

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