Planococcus kenyae
(coffee mealybug)

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Biological Control

Various introductions of parasitoids to control P. kenyae have been listed by Le Pelley (1959). Abasa (1975) also reviewed the use of natural enemies to control P. kenyae and other coffee pests in Kenya between 1911 and 1970. The successive misidentifications of P. kenyae on coffee in Kenya, as P. citri and P. lilacinus, led to searches for natural enemies in the wrong geographical areas (Rosen, 1978). Thus, introductions of parasites of P. citri and large numbers of parasites and predators of P. lilacinus from the Far East all failed to provide control, since the parasitoids tend to be host specific. Later, introductions of parasites of P. kenyae from Uganda proved successful. Of the five parasitoids introduced to Kenya (Anagyrus nr kivuensis, Anagyrus beneficians, Pauridia peregrina, Leptomastix bifasciatus and Pseudaphycus sp.) Anagyrus nr kivuensis, proved to be outstanding, based on the fact that it was hardy, vigorous, adaptable, mates readily and is an excellent searcher. It is capable of maintaining itself on very low and scattered mealybug population, and showed itself capable of controlling infestations even with ants around i.e. without the need to control ants by stem banding with insecticides. Anagyrus beneficians was also quite successful as a control agent, particularly in areas where the mealybug was widespread on indigenous shrubs and herbs and where cultivation was scattered among this vegetation. The other three species all passed several generations in the field, probably established but are not of much importance. Following these introductions, P. kenyae on coffee in Kenya fell from a major pest status and was classified as a minor pest in 1963 (Le Pelley, 1968) and has remained so to date (MH Mugo, Coffee Research Foundation, Kenya; personal communication). Since then, P. kenyae has been hard to find on coffee in most parts of Kenya and it has not been necessary to make further introductions of natural enemies. In 1945, an unidentified hyperparasitoid which had transferred from another host to Anagyrus nr kivuensis appeared able to prevent the parasite from effecting control on coffee when mealybugs occurred on young vigorously growing suckers coming from near the base of the tree. This new development was kept under control by prompt stripping of unwanted suckers and since 1967, only the odd estate has an occasional attack by this hyperparasitoid. The coccinellid predator, Cryptolaemus montrouzieri, was introduced into Kenya from South Africa in 1924 and 1929-30 for the control of P. kenyae on coffee but was preyed upon by attendant ants and was believed to have disappeared. The beetle was, however, found in 1971 some 50 km away from the release site, preying upon Dactylopius indicus, which had itself been introduced from South Africa to control prickly pear (Opuntia) but had not been successful (Greathead, 1972).

Cultural/Integrated Control

Buam (1972) discussed the prospects for the integrated control of P. kenyae and other coffee insect pests. Anon (1990) also presented recommendations for an integrated management strategy for the control of P. kenyae and other coffee pests. The method involved the use of insecticides and poison baits for ant control to encourage predators and parasitoids that would otherwise be killed by the ants. Cultural control of P. kenyae since its introduction from Uganda has entirely consisted of measures to break the association of mealybug and the ant Pheidole punctulata. In the early days, direct spraying and use of poison bait were not effective against the ant. Later, effective control was achieved by banding the tree trunk with some repellent or sticky substance to prevent access of the ant to the mealybug. Under these conditions, the mealybug bred more slowly and the numerous predators present brought the mealybug under control. After the introduction of parasites from Uganda, banding was almost entirely dispensed with but has come back in use in special cases, with the availability of effective chemicals for stem banding. This together with the introduced parasites, has resulted in a form of integrated control that has virtually eliminated P. kenyae as a threat on coffee in Kenya (Le Pelley, 1968). For stem banding to be effective, unwanted suckers and branches touching the ground are removed; also unwanted suckers should be promptly removed. Where the coffee plant is small for stem banding, the tree collar and the mulch around it are sprayed with the chemical.

Chemical Control

Among the earliest chemicals used to control P. kenyae were primitive soap and oil mixtures and methylated spirit used to paint mealybug colonies but these proved ineffective. Then followed the use of poison baits and several chemicals aimed at controlling the attendant ants. These included treating the soil with naphthalene, aradichlorobenzene and other fumigants, using boiling water on ant nests or blow lamps, digging for queens but these were all abandoned. Later castor oil placed on paper bands or paper cones around the trunk gave some weeks of protection but this was superseded by high-boiling point tar obtained by distilling creosote or anthracene oil, a substance which became known as kresotow. It was used on a cloth band over greaseproof paper or painted onto a paper cone (James, 1930) since it was injurious to the bark if applied directly. This method was expensive to apply and was later replaced by banding greases of the tanglefoot type that could be applied directly on the bark with no ill effects. This was integrated with the removal of lower primaries to prevent them touching the ground to form bridges for the ants. Although this method enabled some coffee to be picked on even heavily mealybug-infested plantations, it was only partially effective and was tedious and expensive. After the establishment of introduced parasites, banding was dispensed with. As a direct spray for badly affected trees or on sucker growth, diazinon was recommended, using 60% miscible liquid at a quarter of a pint in 40 gallons (Anon., 1961). Dimefox, a systemic insecticide, was also tried with some success but has not been adopted in practice (Bond, 1953). Chemicals presently being used in Kenya against attendant ants include supracide, chlorpyrifos and rhodocide, in each case adding 15 g Methylene blue. These are applied as a 15 cm-wide stem band on the tree trunk by painting or spraying, followed by the removal of drooping primaries which would otherwise serve as bridges for the ants. Amdro (Hydramethylnon) applied on the soil around the base of coffee trees is also effective against the ants (Anon., 1989).