Rearing Cactoblastis cactorum (Lepidoptera: Pyralidae) on a factitious meridic diet at different temperatures and larval densities

Authors: Marti, Orville; Carpenter, James

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2008
Publication Date: 12/29/2008
Citation: Marti, Orville G., Carpenter, James E. 2008. Rearing Cactoblastis cactorum (Lepidoptera: Pyralidae) on a factitious meridic diet at different temperatures and larval densities. Florida Entomologist. 91:679-685.

Interpretive Summary: The cactus moth is an invasive species not native to North America. It is an economic and ecological threat to native cactus species in the U.S. and Mexico and is the object of an eradication program in both countries. One aspect of the eradication program involves the release of large numbers of sterile moths that were reared on artificial diet or cactus pads in the laboratory. Sterile moths mate with normal wild moths and produce no fertile offspring. We studied 3 different rearing temperatures (22,26 and 29C) and three different crowding levels (50, 215, and 500 eggs) to determine percent survival to the adult stage, size of male and female pupae, and number of eggs produced. All larvae were reared on artificial diet in the laboratory. Temperature and crowding levels affected survival. The lowest rearing temperature and the low and high crowding levels produced the lowest survival rates in the adults. Female pupae were larger than male pupae and size of male pupae, but not female pupae, was affected by rearing temperature. The lowest rearing temperature produced the smallest male pupae. Length and width, but not weight, of female pupae were affected by crowding levels. Female pupae produced at the intermediate crowding level were slightly larger than those produced at lower or higher levels. Weight of pupae was related to percent survival. Larger pupae were produced from treatment combinations that resulted in a higher percent survival to the adult stage. More eggs were laid by females that weighed more in the pupa stage.

Technical Abstract: Cactoblastis cactorum (Berg) is an invasive pest that represents an economic and ecological threat to native cacti in the U. S. and Mexico and that is currently the object of an eradication/control program in both countries. One tactic used to mitigate the threat of this species involves the SIT (Sterile Insect Technique), in which large numbers of larvae are reared on artificial diet or cactus cladodes, preferably the former, and released as sterile adults to mate with wild individuals at or near the leading edge of invasion. We studied combinations of 3 different rearing temperatures (22, 26, and 29 C) and three different crowding levels (50, 215, and 500 eggs) to determine percent survival to the adult stage, pupal size of each gender, and fecundity of C. cactorum reared on a factitious meridic diet. Temperature and crowding levels affected survival. The lowest rearing temperature and the low and high crowding levels adversely affect survival. Female pupae were larger than male pupae and pupal size of males, but not females, was affected by rearing temperature, with smaller male pupae produced at the lowest temperature. Length and width, but not weight, of female pupae were affected by crowding levels, with slightly larger pupae produced at the intermediate level. For both genders, there was significant regression of pupal weight on percent survival, with larger pupae produced from treatment combinations that produced higher percent survival to the adult stage. Number of eggs laid per female was positively correlated with weight of the female as a pupa.