Mealybug nymphs and female bugs suck sap from inflorescence, tender leaves, shoots and fruit stems. As a result, the affected inflorescences and leaves wither and dry out. Migrating females can be found in the tree stems and around the trees on the ground where they lay eggs. Severe infestation affects the fruit set and causes fruit drop. Mealybugs secrete honeydew which provides a perfect substrate for the development of sooty mold. Photosynthetic activity can be critically affected by sooty mold colonies, resulting in poor productivity, defoliation and fruit loss.
The symptoms are caused by Drosicha mangiferae, a mealybug that is specialized on mango trees. At the end of their life cycle of 78 - 135 days, females climb down the trees to lay eggs or hibernate as pupae. Purple-colored eggs are deposited in sacs dug into the roots or into loose soil in a range of 2–3 m around the trees. The eggs remain 6 months in the earth around trees. After hatching, nymphs start ascending the trees to the succulent parts and the fruiting components, where they start sucking sap. Males are winged and short-lived after mating, and hence do not cause any damage to the trees. Mealybugs are spread by wind, rain, birds and even ants, who benefit of the mealybug's excrements.
Use sticky bands sprayed with neem seed extract or garlic oil to deter the bugs. Foliar sprays based on Verticillium lecanii or Beauveria bassiana has proven effective during months with high humidity. Orchards can also be flooded during egg hibernation to decimate the bugs.
Always consider an integrated approach with preventive measures together with biological treatments if available. Sprays containing methomyl, imidacloprid, acetamiprid, buprofezin, deltamethrin and supracide have proven extremely effective in treating mealybugs. It is recommended to spray the entire tree only after severe infestation. Otherwise spray merely the lower stem where mealybugs climb up and down.