Root mealybug (Planococcus citri)
This mealybug is usually a minor pest of coffee, but it is potentially a serious pest. The mealybugs attack the roots where they usually live in association with a fungus (Polyporus sp.), which forms a crust over the mealybugs. Seedlings and very young trees are often free of the fungus. Attacked trees show wilting yellow leaves as if suffering from moisture stress. When affected trees are uprooted, the roots are stunted and encased in brown fungus. When the fungus is pealed off, the white mealybugs can be seen.
Damage is more prominent in dry conditions. The pest is associated with poorly established coffee. Severe infestation may lead to loss of quality, failure of berries to ripen and overbearing and die-back. Identical mealybugs have been reported on Solanum spp., Combretum spp. and Indigofera spp. The root mealybug is also known as the citrus mealybug. It also attacks citrus and cocoa, where it normally attacks the aerial part of the plants.
In the highlands of Java, the shade tree Leucaena glauca is main food plant of citrus mealybug at altitudes above 600m (2000 ft.). Measures that proved successful for the control of citrus mealybug were mainly directed against infestation of this tree and consisted of removing the flower clusters or, when necessary, pruning all foliage and flowers. It is also claimed that citrus mealybug can be controlled by increasing the shade in plantations and that this was undesirable for Robusta coffee but suitable for Arabica at high altitudes. Good results were obtained by providing three covers, one above the other, of Leucaena, Erythrina and Albizia, or with Leucaena and Albizia only. It is further suggested that because the insect infests mainly the flowers and pods of L. glauca, other shade trees that seldom flower, such as L. pulverulenta (L. leucocephala), or a sterile hybrid of L. glauca and L. glabrosa should be planted.
- Strictly observe the recommended nursery management and establishment procedures especially removal of all stem and root remnants. Destroy attacked suckers and do not use them as mulch.
- Uproot affected trees and burn on site.
- Allow infill holes to rest at least for 3 months before replanting in order for the remaining root mealybugs to die.
- Neem treatments have a good effect on mealybugs