Adult survival of Delphastus catalinae (Coleoptera: Coccinellidae), a predator of whiteflies (Hemiptera: Aleyrodidae), on diets of whiteflies, honeydew, and honey.

Delphastus catalinae (Horn) is a coccinellid predator that is commercially sold for the management of whiteflies. A study was conducted to assay the effect of selected diets on the survival of adult D. catalinae. Treatments of water (as a control), 10% honey, honeydew, and whiteflies [Bemisia tabaci (Gennadius)] were provided to the beetles in laboratory assays. Newly emerged, unfed adult insects were used at the start of a survival experiment with trials lasting 50 d. Another survival experiment used mixed-aged adults from a greenhouse colony, and the trials lasted 21 d. Survival was poor on a diet of solely water; ~1% survived beyond a week at 26°C. Survival using the newly emerged insects was similar between those fed honeydew and honey diets, but those on the whitefly diet had the greatest survival (~60% on day 50). However, in the experiment with mixed-aged beetles, adults on honey, and whitefly diets performed the same over a 21-d experiment. Excluding those on the water diet, survival of beetles on the various diets ranged from ~50-80% after 21 d. In an open choice assay across 7 h, D. catalinae adults were found on the whitefly diet in a much greater incidence than on the other diets, and the number of beetles found on the whitefly diet increased over time. The data supports that when D. catalinae are employed in greenhouses or fields for whitefly management, during low prey populations, honeydew from the whitefly can help sustain the population of this predator. Moreover, a supplemental food such as a honey solution can help sustain the population of D. catalinae when the prey is decreased to low numbers. These results may help in the development of strategies to enhance the utility of predators for the management of whiteflies.

Field-level validation of a CLIMEX model for Cactoblastis cactorum (Lepidoptera: Pyralidae) using estimated larval growth rates.

Invasive pests, such as the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), have not reached equilibrium distributions and present unique opportunities to validate models by comparing predicted distributions with eventual realized geographic ranges. A CLIMEX model was developed for C. cactorum. Model validation was attempted at the global scale by comparing worldwide distribution against known occurrence records and at the field scale by comparing CLIMEX "growth indices" against field measurements of larval growth. Globally, CLIMEX predicted limited potential distribution in North America (from the Caribbean Islands to Florida, Texas, and Mexico), Africa (South Africa and parts of the eastern coast), southern India, parts of Southeast Asia, and the northeastern coast of Australia. Actual records indicate the moth has been found in the Caribbean (Antigua, Barbuda, Montserrat Saint Kitts and Nevis, Cayman Islands, and U.S. Virgin Islands), Cuba, Bahamas, Puerto Rico, southern Africa, Kenya, Mexico, and Australia. However, the model did not predict that distribution would extend from India to the west into Pakistan. In the United States, comparison of the predicted and actual distribution patterns suggests that the moth may be close to its predicted northern range along the Atlantic coast. Parts of Texas and most of Mexico may be vulnerable to geographic range expansion of C. cactorum. Larval growth rates in the field were estimated by measuring differences in head capsules and body lengths of larval cohorts at weekly intervals. Growth indices plotted against measures of larval growth rates compared poorly when CLIMEX was run using the default historical weather data. CLIMEX predicted a single period conducive to insect development, in contrast to the three generations observed in the field. Only time and more complete records will tell whether C. cactorum will extend its geographical distribution to regions predicted by the CLIMEX model. In terms of small scale temporal predictions, this study suggests that CLIMEX indices may agree with field-specific population dynamics, provided an adequate metric for insect growth rate is used and weather data are location and time specific.

Life table analysis for immatures and female adults of the predatory beetle, Delphastus catalinae, feeding on whiteflies under three constant temperatures.

Immature development and reproductive life history of Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) feeding on Bemisia tabaci biotype B (Gennadius) (Homoptera: Aleyrodidae) (= B. argentifolii Bellows and Perring) immatures was studied at three constant temperatures: 22, 26 and 30 degrees C. Lower developmental threshold temperatures (T0) were estimated at 9 and 9.9 degrees C, for males and females, respectively. Female adults weighed slightly more than males (0.587 and 0.505 mg, respectively). As temperature increased from 22 to 30 degrees C, developmental time from eggs to eclosion of the adult declined from 24 to 15 days. Thermal units required for immature development was approximately 300 degree-days. Percentage egg hatch declined at increasing temperatures, but no significant effect of time was found. The intrinsic rate of increase, r, increased from 0.048 to 0.082 and doubling time decreased from 14.44 to 8.45 days as temperature increased from 22 to 26 degrees C. Mean daily fecundity was modeled as a function of time and temperature to create a 3-dimensional surface. Overall, Delphastus catalinae was found to perform better at 22 and 26 degrees C while 30 degrees C was detrimental to immature development and adult reproduction.