The Effect of Winter Length on Duration of Dormancy and Survival of Rhagoletis completa (Diptera: Tephritidae) and Associated Parasitoids From Northeastern Mexico

Abstract

The walnut husk fly Rhagoletis completa (Cresson), native to the Midwestern United States and Mexico, is invasive in California and Europe. It is one of the most important pests of walnuts in areas gathering 30% of the world production. Knowledge of life-history regulation is important for the design of management strategies. Research on dormancy has been performed on invasive populations, and not on populations at the southern extreme of its native range. Here, we examined the effect of winter length on fly and parasitoid emergence, survival, and duration of dormancy. Percent emergence was higher for chill periods at 5°C ranging from 8 to 20 wk. No or insufficient chill resulted in low emergence and a significant proportion of individuals in prolonged dormancy (>1 yr). Duration of dormancy was longer for pupae at constant temperatures and a 4-wk chill period than longer winter durations. Dormancy was longer for Mexican than that reported for U.S. populations, suggesting the existence of a latitudinal cline where populations at southern latitudes have evolved slower metabolic rates. Three parasitoid species were found associated with R. completa ( Aganaspis alujai (Wharton and Ovruski) (Hymenoptera: Figitidae), Diachasmimorpha juglandis Muesebeck, and Diachasmimorpha mellea Gahan) (Hymenoptera: Braconidae). Results suggest that rearing of R. completa is possible by subjecting pupae to chill periods between 8 and 20 wk. Overwintering mortality of flies and A. alujai could be further reduced above 5°C. Our findings can contribute for the accurate development of predictive models on invasion potential, development, fly and parasitoid rearing, and biological control.

Eclosion and adult longevity traits ofRhagoletis tabellaria(Diptera: Tephritidae) andUtetes tabellariae(Hymenoptera: Braconidae) in the laboratory

“…For R. tabellaria, longer chill durations result in earlier mean eclosion times for adult flies, albeit eclosion curves showed temporal overlap and time differences were only approximately 10% of the means. A similar relationship has been reported for R. pomonella (Neilson 1962), R. indifferens (Brown and AliNiazee 1977), Rhagoletis cingulata (Loew) (Rull et al 2017), and R. completa (Rull et al 2019). Eclosion of 195-day chill R. tabellaria flies was not statistically different compared with that of 150-day and 120-day chill flies because of the slightly different chilling and adult rearing temperatures used between experiments.…”

“…For example, R. indifferens from the Pacific Northwest of the United States of America eclosed as adults in greater numbers from puparia held at 0-4.4°C for 150 than 120 days (Frick et al 1954) and eclosed progressively earlier after puparia were chilled for 120, 180, and 240 days (Yee et al 2015a). For Rhagoletis completa Cresson from a temperate humid climate in northeastern Mexico, adult eclosion was greater after puparia were held at 5°C for eight than for 0-4 weeks (Rull et al 2019). Given that R. tabellaria is native to the same habitats as R. indifferens, a species that attacks native bitter (Prunus emarginata (Douglas ex Hooker) Eaton; Rosaceae) and cultivated cherries (Prunus Linnaeus species), it can be hypothesised that R. tabellaria displays similar responses to chilling as R. indifferens, even though host plant phenology may influence these responses.…”

Host plant stimuli effects on survival and duration of dormancy ofRhagoletis zoqui,Rhagoletis completa(Diptera: Tephritidae) and associated parasitoids

“…As found in other studies involving Mexican populations of R. completa (Rull et al, 2019a), we recorded 21% parasitism by three hymenopteran species (A. alujai, D. mellea, and D. juglandis). By contrast, parasitism on R. zoqui was almost non-existent, a surprising finding considering the fact that this fly species was collected within its native range and from its natural host plant.…”

“…The latitudinal cline holds true for Mexican populations at the southern extreme of the distributional range of this species (Rull et al, 2016), and appears to include R. cingulata (Rull et al, 2018) which forgo dormancy in proportions under 1%. In the case of R. completa, AliNiazee and Boyce (1931) reported up to 75% and 53% of non-dormant individuals while Rull et al (2019a) and our current results failed to detect any non-dormant individuals for the Mexican population in this species. Similarly, very few R. zoqui individuals forgo dormancy (Rull et al, 2016).…”

“…Both species become dormant as pupae to synchronize adult emergence with seasonal host fruit availability (Rull et al, 2016(Rull et al, , 2019a. Two parasitoid species have been found in exclusive association with walnut infesting Rhagoletis, Aganaspis alujai and Diachasmimorpha juglandis (Rull et al, 2013), both parasitoids also become dormant and emerge as adults later than their fly hosts (Rull et al, 2019a). Considering the tight relationship between the phenology of Juglans fruits and adult emergence of walnut infesting Rhagoletis, here we tested the hypothesis that host plant chemicals influence adult emergence rates and emergence time of both species and their parasitoids.…”