Larval food influences temporal oviposition and egg quality traits in females of Lobesia botrana

Many phytophagous insects are agricultural pests, and control methods require accurate monitoring and decisions based on the determination of population age structure. The reproductive output (fecundity, egg size and percent egg hatch) is a central life history trait because it determines the offspring number, and temporal oviposition patterns are of primary importance in conditioning larval hatching and the occurrence of later larval instars in time. In turn, these phenomena determine the window for natural enemy attack and thus impact the context of biological control programmes. In addition, for most phytophagous insects, the quality of the host plants that larvae consume determines the insects' reproductive output. The purpose of the present study was to determine whether the number of eggs laid, egg size and egg hatch percentage vary with female age and the cultivar on which females develop as larvae, as well as the temporal effects of these parameters. This determination was performed in laboratory experiments where larvae were reared on artificial diets based on dried fruits of seven cultivars. Our results showed that the cultivars had a significant effect on female temporal oviposition. Independent of the food tested, the numbers of oviposited eggs, their size and percent egg hatch decreased with daily oviposition rank. Such temporal patterns must be incorporated in age-structured mathematical models used in the design of control strategies. Temporal oviposition and variation in egg quality traits will also be useful in biological control programmes, especially when based on egg or larval parasitoids, which is thus discussed.