Watermelon crop is attacked by many insect pests, of which leaf miner assumes significance as it causes greater damage.
Leaf miner menace in watermelon
The larvae feed on the leaves by mining into them. Smaller leaves with limited feeding space are characterised by a secondary blotch.
Damage caused by a single larva is minimal. However, when the population is heavy they are capable of destroying more leaves and affect the growth of the plants.
Foliage punctures made by females during oviposition or feeding cause stappling of leaves. Yellow and white to brown tunnels or blotches will be seen between the upper and lower surface of leaves.
These tunnels form all over the leaf making loops. Severely affected leaves curl, turn brown and die.
Eggs are oval in shape and creamy white in colour and are laid singly in punctures on the epidermis of the leaf. There are three larval stages. Entire larval period lasts for 7-9 days after which the pupal stage starts. Pupae are oval shaped with narrow ends. Adults are small, grey coloured flies with black and yellow markings and live for about 10-20 days, depending on the environment.
Collect and destroy damaged leaves along with larvae and keep the field weed free.
Installation of yellow, sticky traps is effective. The traps should be placed in and around the field at about 10 cm above the foliage.
Avoid water stress in irrigated crop. Dusting the leaves with phosalone 4D at 25 kg/ha or carbaryl 10D at 25 kg/ha or spraying of endosulfan 35EC at 750 ml/ha or Dichlorvos 76 WSC at 625 ml/ha will be effective.
& K. Ramaraju
Coimbatore, Tamil Nadu
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