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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #220919
Title: Chemical desilking of Cactoblastis cactorum Berg pupae

Author
item Marti, Orville
item Carpenter, James

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2008
Publication Date: 7/1/2008
Citation: Marti, O.G. and Carpenter, J.E. 2008. Chemical desilking of Cactoblastis cactorum Berg Pupae. Journal of Entomological Science 43(3):344-347.

Interpretive Summary: The South American cactus moth, 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 eradication/control programs 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 in the laboratory and released as sterile adults to mate with wild cactus moths. Whether reared on cactus cladodes or artificial diet, the larvae pupate in silken cocoons make handling difficult. For experimental purposes, as well as for mass rearing, it is often necessary or desirable to have pupae free from the silk cocoons. Pupae can be removed from cocoons manually, but the process is less labor-intensive and much faster if the pupae are desilked chemically. We examined the exposure time that was required to remove the silk and whether the adult moths could emerge successfully from the pupa following chemical removal of the cocoon silk. We found that 18 seconds exposure to undiluted (6%) sodium hypochlorite, followed by 2 minutes rinsing in running tap was sufficient to remove the silk without harming the pupae. Diluting the sodium hypochlorite increased the time required to remove the silk but did not increase the percentage of successful emergence of adults from the pupa. Exposure of pupae to higher relative humidity following chemical removal of the silk did not affect percent emergence of adults.

Technical Abstract: We conclude that de-silking of C. cactorum cocoons with NaOC1 is a fast and safe procedure that does no great harm to pupae when used as recommended. The effect of low humidity following de-silking was not found to be detrimental to C. cactorum. Nevertheless, we prefer to maintain a high RH in the mass-rearing facility for C. cactorum at CPMRU because small but statistically non-significant treatment effects can still amount to large differences in a rearing facility in which many thousands of insects are reared.