Problem Statement: In 1923, an introduced mealybug became a serious problem on arabica coffee in the Kenya highlands, causing up to 10 per cent crop loss, death of some coffee trees, and incurring considerable costs in attempts at chemical control. Repeated misidentification of the pest, with attendant failed biological control efforts resulted in over 15 years of crop losses to the Kenyan coffee industry.

Methods: The pest was initially identified as Pseudococcus citri Risso, and natural enemies of this mealybug were imported to Kenya from outside Africa for several years from 1924. These failed to establish and the infestation continued to spread in spite of the use of expensive pesticides and massive releases of cultured local predators (inundative biological control). In 1933 the mealybug was re-identified as P. lilacinus Cockerell, and in 1936-37 searches in Indonesia, the Philippines, Sri Lanka and southern India located several natural enemies for screening. However, despite expensive screening processes, these also failed to impact on the pest.

Meanwhile, it had been shown taxonomically that the pest was biologically and morphologically different from P. lilacinus. In 1935 it was described as P. kenyae, a species new to science (now known as Planococcus kenyae), and subsequently was found to be native to Uganda (the area of origin of coffee). Hymenopteran parasitoids were collected from Uganda and five species were selected for screening and introduction in 1938. One (Anagyrus sp. nr kivuensis) proved to be especially effective at suppressing the mealybug and the pest has remained under good control since 1941.

Outcomes and Impacts: In the 1920s, taxonomic knowledge of mealybugs in Africa was limited. The pest was misidentified twice, each time resulting in the introduction and failure of natural enemies introduced from South East Asia. Once the correct area of origin was located as a source of natural enemies, establishment of effective biological control was achieved in 3 to 4 years. It was estimated that by 1959 the project had saved Kenya at least £10 million for an outlay of less than £30,000. No new calculations on subsequent savings are available. As a result of this case, the taxonomy of African mealybugs was subsequently studied more thoroughly to try and prevent similar outbreaks.

Lessons: The 15-year time-lapse between outbreak and control was due to the poor taxonomic knowledge of African mealybugs at the time. Misidentification of the pest caused misdirection of the control effort on two successive occasions. This demonstrates how inadequate taxonomic input can adve