- The initial attack is usually restricted to outer most whorls of leaves.
- The caterpillar feeds on the surface tissues from the under surface of leaf lets.
- The areas from which surface tissues have been eaten turn brownish and dry up.
- The dried up patch gradually extends all along the leaf lets.
- In due course the dried areas of leaf lets may break up and drop away when agitated by wind.
- All or some of the leaf lets of a frond are damaged in this way.
- The attack which is confined to lower fronds may extend to higher leaves also as the attack advances.
- When many fronts are attacked in this way the tree looses its bearing capacity.
- The attack occurs only once in few years in most areas ;but it is seen regularly in endemic areas.
Select 20 trees at random from a plot and assess the intensity of damage. Mild: When the damage is restricted in the outer whorl of leaves Moderate: When the symptoms extends to inner whorls of leaves.
When the damage symptom crosses the outer whorl of leaves and seen in one upper leaf in at least one among the selected trees.
- As a prophylactic measure the first affected leaf may be cut and burnt during the beginning of summer season.
- Arrange for the release of larval or pupal parasitoids such as bethylid, (Goniozus nephantidis) for third instar larva; Elasmid,(Elasmus nephantidis), for the pre pupal instar and Chalcid, (Brachymeria nosatoi) for early pupal instar.
- The bracorid (Bracon brevicornis) can also be released as a larval parsitoid.
- Trunk release of Goniozus nephantidis @ 10 per palm (4-6 releases) is effective for management of leaf caterpillar.
- When infestation is severe and if biocontrol is not likely to be effective spray the under surface of fronds with dichlorvos (0.05%) malathion (0.1%),quinalphos (0.05%) or phosalone(0.07%).
- Application of the insecticide should be followed by liberation of larval and papal parasitoids from the 21st day.