The symptoms are most prominent on the leaves. Larvae feed on tender leaves by scraping the epidermal surface in between the veins. Then they feed on these leaves voraciously, leaving behind the midrib and veins. This results in clusters of dry, webbed and withered leaves. Under severe infestation, shoots become dry, thus restricting photosynthesis. The affected trees appear unhealthy and can be easily detected due to their brown, dried and clustered leaves. Flower stalk formation is affected which in turn affects flowering and fruiting processes.
Damage is caused by the larvae of Orthaga euadrusalis. Female moths lay yellowish green dull-colored eggs on mango leaves which usually hatch within a week. Depending on the weather conditions, the larval period may vary between 15 and 30 days as there are usually five larval instars. After the last instar, the larvae pupate in the web, fall on the ground with a jerk, and continue the process in the soil. The pupal period may vary between 5 and 15 days, depending on the temperature. Densely planted orchards have higher infestation rates than the normal-spaced and canopy managed orchards. The insect infestation usually starts from the month of April and continues up to December. The relative humidity is significantly correlated to leaf webber population.
Use natural enemies of leaf webber parasitoids such as Brachymeria lasus, Hormius sp. Pediobius brucicida, and natural predators such as Carabid beetle and reduviid bug. Spray Beauveria bassiana two or three times during the period of highest humidity.
Always consider an integrated approach with preventive measures together with biological treatments, if available. Three sprays are recommended at 15 days interval, with Quinalphos (0.05%). Spray chemicals based on lambda-cyhalothrin 5 EC (2ml/liter of water) or Chlosopyriphos (2 ml/l), Acephate (1.5 g/l).