Biological control of the coconut scale insect (Aspidiotus destructor Sign. Homoptera: Diaspididae) in the southern region of Oman (Dhofar).
The monitoring of population levels of Chilocorus nigritus [C. nigrita], which was successfully introduced from India during 1985 as a biocontrol agent of Aspidiotus destructor (a pest of coconut palms) in south Oman, is described. A total of 683 adults of C. nigrita was released during January-April 1985. Data indicated a rapid build-up of predator numbers and a subsequent decline in the host population. After 24 months from the last release date (April 1985), the median number of pest insects per leaf area fell to between 0 and 49.7, whereas pest numbers before the release ranged from 174.8 to 285.0. Numbers of C. nigrita built up rapidly at the release site and up to 12 km from the release site 6 months after the last release (38.2-144.5 predators (adults and larvae combined) per palm). C. nigrita was also found at Taqa, 16 km from the release site, 18 months after the last release. Numbers of A. destructor were greatly reduced at the release site and at all locations studied throughout the Dhofar plain 24 months after the last release. It is concluded that the efficiency of C. nigrita as a predator of A. destructor was such that pesticides were no longer required for the control of the latter in the southern region of Oman.