Observations on Proutista moesta (Westw.) (Homoptera: Derbidae), the Vector of Palm Diseases in Kerala State, India

The plant hopper, Proutista moesta (Westw.) is an economically important sap-sucking insect of palms and is implicated as a common vector of root (wilt) disease of coconut, yellow leaf disease of arecanut and spear rot disease of oil palm in Kerala state, India. The adults are sap feeding, while its nymphs develop saprophytically by feeding on substrates undergoing fungal decomposition. Oil palm agro-ecosystem provides P. moesta with abundant breeding substrates. The rotting smell and rose colour of the fungus, Neurospora sp, which grows profusely on oil palm bunch waste, attracts P. moesta for oviposition. P. moesta is always seen in feeding position. No hopper burn or feeding mark develops due to its feeding. The feeding punctures made by it on the ventral side of the leaves are also not visible to the naked eye. Among the leaflets of a frond of an oil palm, 40 to 80 from the basal end are preferred for feeding. From the base, about 20 cm portion of the leaflet attracts more adults. It also shows preference to 10 mm area on either side of the mid rib for feeding. Early stage spear rot diseased oil palm attracts 4.84 times more P. moesta than the nearby healthy palms. The outer fronds directed towards North and South of an adult palm with yellow and green leaflets attracted 2.64 times more P. moesta than those directed towards East and West. Stephanitis typica is another vector of root (wilt) disease of coconut, which on migration to oil palm, may cause spear rot disease in India. P. moesta and S. typica show some similarities and differences in feeding and breeding behaviours. Normally, both are short distance fliers and many adults feed from the ventral side of the leaflet. Adults and nymphs of S. typica produce hundreds of permanent feeding marks on the dorsal side of the leaves. S. typica adults prefer to feed on the just unfurled leaves of coconut, while the adults of P. moesta feed on the outermost leaves. In recent years, P. moesta accepted oil palm as its most favoured food plant, but for S. typica, coconut palm remains to be its important host.