Canola, corn, and vegetable oils as alternatives for wheat germ oil in fruit fly larval diets

Abstract

Four wheat germ oil alternatives (corn oil, vegetable oil, canola oil with 10% vitamin E, and canola oil with 20% vitamin E), purchased from a local supermarket in Hawaii, were added to a fruit fly liquid larval diet as a replacement for wheat germ oil in the rearing of fruit fly larvae. The oils were tested on three species of fruit flies in Hawaii, Ceratitis capitata (TSL strain), Bactrocera dorsalis, and Bactrocera cucurbitae. They were evaluated for their efficacy in replacing WGO, based on: pupal recovery (%), larval duration (d), pupal weight (mg), adult emergence (%), adult fliers (%), mating (%), egg production per female per day, egg hatch (%), and peak egging period (d). Diets with WGO and without any oil were used as controls. The objective of the study was to select the most cost effective alternative oils with the best performance to replace the currently used WGO, which is pricey and hard to find. The results showed that there was no significant difference in performance among the tested oils in B. cucurbitae and B. dorsalis as regards the above mentioned parameters. Lower mating rate was observed in B. cucurbitae from those reared in vegetable oil and canola oil (10% vitamin E) diet. Lower egg production and egg hatch were obtained with B. dorsalis whose larvae were reared in vegetable and canola oil (both 10% and 20% vitamin E). Vegetable oil diet seemed to reduce pupal weight, shorten larval duration, and increase pupal recovery of C. capitata. The results suggest that WGO can be substituted with corn oil, vegetable oil, or canola oils for B. cucurbitae, while corn oil is a better alternative for B. dorsalis, and vegetable oil is best for C. capitata.