Effects of temperature and dietary sucrose concentration on respiration in the silverleaf whitefly, Bemisia argentifolii.
A system consisting of a flow-through chamber connected to a commercial infrared gas analysis system was developed to measure homopteran respiration during feeding. Using this system, respiration rates of 202 and 206 µmol CO(2) h(-1) g(-1) (4.96 and 5.04 ml CO(2) h(-1) g(-1)) were determined for whiteflies and cotton aphids, respectively, at 25 degrees C on diets containing 15% sucrose. These rates were considerably higher than those of other stationary insects, indicating that whiteflies and aphids maintain a relatively high metabolic rate when feeding. Whitefly respiration increased with temperature from 25 to 46 degrees C with a Q(10) of about 2 on diets containing 10, 15 and 20% sucrose, but less than 2 on diets containing 2.5 and 5% sucrose. Respiration rates were similar on the diets containing >10% sucrose, but were generally lower on the diets containing <10% sucrose. Respiration rates decreased upon extended exposure to 47 degrees C; the rate of decrease was inversely related to the dietary sucrose concentration up to 15%. The results indicate that whiteflies require a sucrose concentration of between 5 and 10% (i.e. 0.15 and 0.3 M) for maximum rates of metabolism while feeding. Higher concentrations of sucrose in the diet delayed high-temperature mortality, possibly a reflection of the high sucrose requirement for sorbitol synthesis in whiteflies.
Salvucci
ME
US Department of Agriculture, Agricultural Research Service, Western Cotton Research Laboratory, 4135 E. Broadway Road, 85040-8830, Phoenix, AZ, USA
Crafts-Brandner
SJ