The bioecology of Psylla uncatoides in the Hawai`i Volcanoes National Park and the Acacia koaia sanctuary

Leeper, John; Beardsley, J

Psylla uncatoides is a recent accidental introduction t o the Hawaiian Islands. Its population densities are closely t i e d t o the flush phenology of Acacia spp. The psyllid was studied on Acacia koa - on the southeastern slope of Mauna Loa above 4000 ft. and on Acacia koaia on the southern slope of Kohala M t . (3200 ft. ). Psyllid counts were broken down into four categories: eggs, small nymphs, large nymphs, and adults. Terminal samples were taken t o obtain egg and nymphal population estimates. Adult popuLations were estimated from three minute D-VAC sarriples. The percent new terminal growth was estimated at the time of each sample. A strong relationship between peak psyllid populations and flush die-back was observed. It was suspected that the psyllid is aiding in the spread of koa rusts, as 63% of 179 psyllid adults observed had rust spores on their integument. Several predatory insects, principally coccinellid beetles and Neuroptera, were found associated with psyllid infestations, but none were satisfactorily controlling the psyllid. No parasites or diseases of the psyllid were found in the State. We plan t o evaluate the effectiveness of additional natural enemies which are being introduced from Australia, the apparent native home of the psyllid, Possible associations of other insects with the psyllid have been observed and will be investigated.