Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2006
Publication Date: 4/1/2007
Citation: Simmons, A.M., Legaspi, J.C. 2007. Ability of Delphastus Catalinae (Coleoptera: Coccinellidae), a Predator of Whiteflies (Homoptera: Aleyrodidae), to Survive Mild Winters. Journal of Entomological Science. 42:163-173. Interpretive Summary: The B-biotype sweetpotato whitefly is an economically important insect pest of vegetables, ornamentals, and other crops. Delphastus catalinae is a small lady beetle which feeds on whiteflies. This beneficial beetle is sold by some biological control companies to help control whiteflies. The beetle is tropical in origin, but wild populations are known to survive in southern California and in central and south Florida. A study was conducted to determine the ability of D. catalinae to survive mild winter areas where the sweetpotato whitefly survives year-round, such as coastal South Carolina and northern Florida. In field tests, only a few beetles survived each of two winters in Charleston, SC and Tallahassee, FL. Laboratory tests indicate that the beetles can live as long as 9 months at a temperature of 59 F. Beetles held at 41 F lived up to 16 days. Without a source of food, their lives were shortened by about 90%. Beetles that were least 8-month old still produced eggs which hatched. Eggs held at 41 F did not hatch; less than 50% of eggs held at 59 F hatched, but they did not survive to the adult stage. However, nearly all eggs hatched at 77 F and nearly 90% of them reached the adult stage. Based on our study, temperatures near freezing can kill a major portion of the beetles, but if such low temperatures last only a short time (such as a few hours), some may still survive. These results may be useful for commercial rearing and for understanding climatic conditions that may affect this predator as a biological control tool against whiteflies.
Technical Abstract: Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) is a predator of whiteflies. It is sold commercially by some biological control industries to help manage Bemisia tabaci (Gennadius). This beetle is tropical in origin, but feral populations in the USA are known to survive in southern California and in central and south Florida. A study was conducted to determine the ability of D. catalinae to survive mild winter areas where B. tabaci survives year-round, such as coastal South Carolina and northern Florida. Sampling from field cages was conducted from December to April in 2002-2004. Only a few individuals were recovered at the end of each winter. Laboratory tests indicated that at a constant temperature of 15 C, the adults can live as long as 9 months (269 d), while those at 5 C lived up to 16 d. Without a source of food, adult longevity was lessened by about 90%. A sample of the population from a laboratory test indicated that old females (at least 242 d old) still produced viable eggs. Eggs held at 5 C did not hatch; less than 50% of those held at 15 C hatched, but the larvae did not reach the adult stage. Conversely, almost all of the eggs held at 25 C hatched, and nearly 90% of them reached the adult stage. We conclude that a winter with low temperatures near freezing can result in a major decimation of a population of D. catalinae, but if low temperatures are not sustained for an extended duration (e.g., only a few hours) some may persevere. These results may be useful for commercial rearing and for understanding climatic conditions affecting this predator as a biological control tool against whiteflies.