Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/5/2007
Publication Date: 3/1/2008
Citation: Simmons, A.M., Legaspi, J.C., Legaspi, B. C. 2008. Responses of Delphastus catalinae (Coleoptera: Coccinellidae), a Predator of Whiteflies (Hemiptera: Aleyrodidae), to Relative Humidity: Oviposition, Hatch and Immature Survival. Annals of the Entomological Society of America. 101:378-383. Interpretive Summary: Delphastus catalinae is a small lady beetle that eats whiteflies. It is tropical in origin. Whiteflies are problems in many agricultural crops in humid and dry climates. A study was conducted to determine the effects of humidity on this beetle. As compared with high humidity, low humidity of 10-25% had a negative effect on the beetles. Egg hatch, survival during development, and size of the beetles were reduced when exposed to low humidity conditions. For insects, size is often related to quality of the insect. Therefore, high humidity may result in more beetles that are high quality. High-quality predators (such as this beetle) are useful for whitefly control. Results from this study help in understanding conditions for rearing the predator and its use in controlling whiteflies.
Technical Abstract: Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) is a predator of whiteflies. It is tropical in origin. Whiteflies are agricultural problems in environments ranging from humid to arid conditions. A study was conducted to determine if there were any humidity effects on oviposition, hatching, and survival of immature D. catalinae. Comparative tests were conducted among relativities humidities (RH) of 25, 35, 50, and 85%, and between 10 and 85% RH. The study was conducted using the B-biotype sweetpotato whitefly, Bemisia tabaci (Gennadius), as the host on collard, Brassica oleracea ssp. acephala de Condolle. Egg hatch and survival to the adult stage were reduced with a reduction in ambient moisture. At 85% RH, 99% of the eggs hatched and about 90% of the beginning cohort survived to the adult stage. Conversely, about 85% hatched and 50 to 60% survived to the adult stage at 10 and 25% RH, respectively. Moreover, adult body weight was significantly reduced with a reduction in percent relative humidity during the development of both immature male and female D. catalinae. The results also suggest that immature D. catalinae density and/or limited food may affect survival and size of the adults. These results help in the understanding of the ecology of D. catalinae, and indicate that extremes in ambient moisture can have an impact on the population of this predator.