Cold susceptibility and disinfestation of bactrocera invadens (Diptera: Tephritidae) in oranges
To develop a cold disinfestation treatment for the fruit fly Bactrocera invadens Drew, Tsuruta & White (Diptera: Tephritidae) that is rapidly spreading across Africa, research was conducted in Nairobi, Kenya, using flies from a laboratory culture and 'Valencia' orange (Citrus sinensis L. Osbeck) as the host. The developmental rate of B. invadens in Valencia oranges was determined at 28°C, and the third instar was found to be the least susceptible of the egg and larval life stages to cold treatment at 1.1°C in oranges. When 22,449 B. invadens third instars were exposed in oranges to a cold treatment with an approximate midpoint of 1.1 ± 0.5°C, the results suggested that a period of 16 d would be worthwhile verifying on a larger scale in oranges. Results from the first replicate of 16,617 larvae showed no survivors, but the second replicate of 23,536 larvae had three survivors. Because a longer cold treatment based on a mean temperature of 1.1°C would create logistical difficulties for some export markets, further replicates were conducted at an approximate midpoint of 0.5°C and at mean hourly maximum of 0.9 ± 0.5°C, for 16 d. After three replicates, in which 65,752 B. invadens third instars in total were treated with no survivors, the Japanese requirement of 99.99% mortality at the 95% confidence level was surpassed. The following treatment protocol for B. invadens larvae in oranges can therefore be recommended: fruit pulp to be maintained at temperatures of 0.9°C or lower for 16 consecutive days. © 2011 Entomological Society of America.