A field evaluation of the sexual competitiveness of sterile melon flies, Dacus (Zeugodacus) cucurbitae

ABSTRACT.

• 1 The sexual competitiveness of sterile melon fly males [Ducus (Zeugodacus) cucurbitue Coquillett] was estimated under field conditions.
• 2 The value of competitiveness was about 0.8 for flies in the fifth to tenth generation from the beginning of mass-rearing, but decreased to about 0.2 in the eighteenth generation.
• 3 The sexual competitiveness estimated using laboratory data was near unity even in the final stage of our study.
• 4 It was concluded that the field evaluation of sexual competitiveness is essential to determine the quality of the insects reared for purposes of pest control.

     

Demography of a native strain of the melon fly, Dacus cucurbitae, from Hawaii

Preadult development and survival rates for a wild strain of melon fly in Hawaii were examined when reared on six common hosts at 25°C. These data were combined with information gathered on adult survival, fecundity and fertility in order to construct life tables.The duration of the egg stage was slightly over 1 day for this species. Depending on host, larval-to-adult development and survival rates were 17–20 days and 35–85%, respectively. Gross fecundity (total eggs) was 1293 eggs/ while net fertility (total fertile eggs weighted by hatch and adult survival) was 518 fertile eggs/. The finite rate of increase () for the species was conditional on the host on which it was reared and ranged from 1.08 to 1.12. The percent of adults in the stable age distribution averaged around 14% over all hosts.

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Démographie d'une souche de Dacus cucurbitae Coquillet, originaire d'Hawaii

Résumé Le développement préimaginal et les taux de survie d'une souche sauvage de D. cucurbitae de Hawaí sur six hôtes courants ont été examinés à 25°C. Ces résultats ont été combinés aux informations récoltées sur la survie des adultes, la fécondité et la fertilité pour réaliser des tables de vie.La durée du stade oeuf est légèrement supérieure à un jour pour cette espèce. La durée de développement de l'éclosion de l'oeuf à l'imago et les taux de survie ont été respectivement de 17 à 20 jours et de 35 à 85% suivant les hôtes. La fécondité brute (ponte totale) a été de 1293 oeufs par femelle, tandis qui la fertilité (nombre total d'oeufs fertiles pondéré par les taux d'éclosion et de survie des adultes) était de 518 oeufs fertiles par femelle.Le taux d'accroissement () variait de 1,08 à 1,12 suivant l'hôte sur lequel D. cucurbitae a été élevé. La proportion d'adultes dans une distribution en âge stable était d'environ 14% sur tous les hôtes.

     

Number of generations necessary to attain eradication of an insect pest with sterile insect release method: A model study

Simulation of the sterile insect release process was carried out based on a system which consisted of a logistic population model and Poisson-binomial model for normal, sterile and combined matings. From the results, relationship between the intrinsic rate of natural increase and the sterile vs. normal ratio necessary to attain eradication of the target pest species were presented. The effects of weakened sperm competitiveness and the increased number of matings per female were not so strong. On the other hand, a given rate of immigration could be a cause of failure of the eradication. A simple method to calculate relationship between hatchability and sterile vs. normal ratio was presented.