Mango flower drop is often mistaken for a nutritional deficiency, but where does the problem actually lie !

Souvik Barman : Mango (Mangifera indica L.) is one of the oldest and important fruit grown in tropical and sub-tropical regions of the world. Although mango produces a large number of flowers, only about 1% successfully set fruit, while the remaining 99% are lost due to various biotic and abiotic factors.

 Growers often fail to identify the cause of flower and fruit drop and assume it is due to nutrient deficiency, whereas in most cases it is caused by pest infestation. More than 50 insect pests have been recorded causing damage to mango crop but the mango leafhoppers are serious pests of mango, particularly at the flowering and fruiting stages.

 Proper flower management plays a critical role in ensuring successful yield and returns.

Three species of mango hoppers viz., Idioscopus nitidulus, I. clypealis and Amritodus atkinsoni are commonly found all over India, with Amritodus atkinsoni is predominant in west Bengal agro-climatic zone. These leaf hoppers were found in large numbers on the mango trees throughout the hot weather, especially at the flowering season and their increase appeared to be assisted by damp winds such as the eastern winds during February and March. Growers can identify it by observing that the insect is small, dark brown in colour, has black lines on its face, jumps quickly when disturbed, and is commonly seen on mango flowers and tender shoots. Females laid about 200 eggs inside the new leaves and inflorescence that hatched in 4-7 days. 

This was followed by 4 to 5 nymphal instars of about 18-20 days duration. Nymphs and adults suck sap from the inflorescence, causing shedding of flower buds and flowers. Leaf hoppers excrete massive quantities of honeydew which imparts sugary shine to leaves and fruits and other plant parts and encourages growth of fungi Capnodium mangiferum and Meliola mangiferae, giving rise to growth of sooty mould that reduces photosynthetic efficiency of leaves and market quality of fruits. 

About 60-100 percent of fruit yield losses have been recorded due to mango hopper. The management of these hoppers has become increasingly difficult because the continuous use of the same synthetic chemicals has resulted in resistance. Before using synthetic chemicals, growers should follow clean cultivation and pruning to increase supply of light and air, as darkness and dampness are associated with increased population and rapid multiplication of this pest. Mango is dependent on cross-pollination, and blowflies (family Calliphoridae) have been reported as major pollinators in India; therefore, the use of synthetic chemicals that are non-harmful to beneficial insects is recommended. Pymetrozine 50% WG, a novel synthetic insecticide, is recommended as a foliar spray at 100–200 g ha⁻¹; its targeted mode of action ensures effective pest control without adversely affecting pollinators. Pymetrozine is non-carcinogenic, shows no adverse effects on birds and earthworms at recommended doses, and has low environmental persistence due to rapid degradation in soil and water. Pymetrozine 50% WG is available in the market under the trade names Chess, Pylon 50 WG, Clue, and Pymate.

Author : M.Sc. Scholar, Department of Agricultural Entomology, Bidhan Chandra Krishi Viswavidyalaya