Young caterpillars soon after hatching, start mining the epidermal layer on the upper surface of the tender cashew leaves, leaving tortuous markings. Later on, the thin epidermal mined areas swell up.
As a result, the affected areas form blistered patches of greyish white colour. When the infested tender leaves mature, big holes are manifested in the damaged areas.
The results of injury are the permanent damage to the young leaves which are shrivelled, dried and shed prematurely.
Nursery seedlings and young plantations are more prone to the infestation of this pest than the older ones.
Normally 3 to 8 blisters and as many as eight caterpillars are observed on a single leaf.
Management
Apply neem oil emulsion (20 ml neem oil/litre of water). Collect and destroy the damaged plant parts.
Spraying may not be required since, natural enemies especially larval parasitoids manage this pest even up to 50 per cent.
Two larval parasitoids viz., Chelonus sp. and Sympiesis sp. are recorded on leaf miners in Kerala and Goa. Besides, Chyrsocharis sp., Aprostocetus sp. and Closterocerus sp. (Eulophidae) are recorded in Puttur region of Karnataka.
