Abstract
Simple SummaryThe Mediterranean fruit fly, Ceratitis capitata, is a pest of fruit and vegetables in many parts of the world. The Sterile Insect Technique (SIT) is used as an environmentally friendly method for the control and/or eradication of this pest. A critical step in the production of sterile insects in biofactories is when the larvae complete their development and begin metamorphosis to become pupae. Artificial substrates are used to facilitate pupation, but little research has been devoted to this critical moment in the life cycle of the insect. We tested seven pupation substrates and five substrate volumes for a reproductive colony of C. capitata VIENNA 8 genetic sexing strain for SIT application in Mexico. One type of cellulose and sawdust at relatively low ratios of substrate:larvae enhanced pupation and were more cost-effective to produce one million pupae than other substrates including fine wheat bran currently used in a SIT mass-rearing facility in Mexico. Our study contributes to improving rearing processes involved in SIT-based pest control.Adequate pupation substrates and substrate volume are critical factors in the mass-rearing of insects for Sterile Insect Technique (SIT) applications. To identify an ideal pupation substrate for a reproductive colony of Ceratitis capitata (Wiedemann) VIENNA 8 genetic sexing strain, we first examined pupation in cellulose from recycled paper (cellulose I), sawdust, fine wheat bran, vermiculite and coconut fiber using a volume of 2.5–12.5 mL of substrate for each 5 mL volume of fly larvae. We found a positive relationship between substrate volume and pupation, with cellulose I generating the highest proportions of pupation and coconut fiber the lowest. Higher proportions of female flies (white pupae) pupated in sawdust. The proportion of female fliers increased as substrate volume rose in sawdust and coconut fiber, whereas it decreased in vermiculite and cellulose. In a second experiment, we tested three types of cellulose differing in physicochemical characteristics (celluloses I, II and III), sawdust, and fine wheat bran using a substrate:larvae ratio of 1:1. The three types of cellulose produced the highest pupation levels. The highest proportions of female fliers were observed in sawdust, and cellulose types III and II. Cellulose III and sawdust at relatively low volumes were more cost-effective to produce one million pupae than other substrates, including fine wheat bran used in a mass-rearing facility in Mexico.
Highlights
The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is a highly polyphagous species native to Africa that has invaded most tropical and subtropical regions of the world [1,2]
We focused on female flies, as this is the most valued sex in the rearing process of reproductive colonies of C. capitata VIENNA 8 genetic sexing strain (GSS) carrying the tsl mutation
A significant interaction between substrate type and volume affected the proportion of female fliers (F 4, 38 = 3.0, p = 0.0305); the proportion of female fliers increased as a function of the volume of substrate only in the case of sawdust and coconut fiber, whereas in the case of cellulose and vermiculite the proportion of female fliers decreased as a function of the volume of substrate used, and in the case of fine wheat bran the proportion of female fliers was similar across the range of substrate volumes used (Figure 1d)
Summary
The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is a highly polyphagous species native to Africa that has invaded most tropical and subtropical regions of the world [1,2]. In Mexico, the Moscamed mass-rearing facility, in Metapa de Domínguez, Chiapas, produces an average of 500 million male pupae of C. capitata VIENNA 8 genetic sexing strain (GSS) per week for SIT releases [7,10]. The VIENNA 8 GSS is based on the white pupae (wp) and temperature sensitive lethal (tsl) mutations [11]. These mutations result in the death of female insects following high-temperature treatment (34 ◦ C) during the egg stage and allow separation of pupae by color (female and male pupae have white and brown puparia, respectively) [12,13,14].
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