Prospects for Biological Control of Macadamia Felted Coccid in Hawaii with Metaphycus macadamiae Polaszek & Noyes, a New Encyrtid Wasp Native to NSW Australia

Abstract

Macadamia Felted Coccid (MFC), Acanthococcus ironsidei (Williams) (Hemiptera: Eriococcidae) was first discovered in 2005 on the Island of Hawaii. Host plants are restricted to Macadamia species, with Macadamia integrifolia Maiden & Betche (Proteaceae) being grown in Hawaii for nut production. Approximately 16,900 acres of macadamia nuts are harvested in Hawaii with estimated farm value of $ 48.8 million (2019 - 2020 records). MFC has become a problem in macadamia orchards where heavy infestations cause the death of young seedlings, reduction in nut production, and severe damage can eventually kill affected trees. Chemical control and extant natural enemies have not suppressed the population of MFC to a manageable level. Exploration in Australia started in November 2013 for the evaluation of potential parasitoids being host specific for introduction into Hawaii. A dominant solitary endoparasitoid of MFC from New South Wales was discovered and described as Metaphycus macadamiae Polaszek & Noyes sp. n (Hymenoptera: Encyrtidae: Encyrtinae). Biology and host specificity testing were conducted at the Hawaii Department of Agriculture, Insect Containment Facility on nine Hemipteran and three Lepidopteran eggs. Results indicated that M. macadamiae is host specific to MFC. There has been no evidence of parasitism or host feeding on any of the non-target insect hosts that were tested. Parasitoid emergence from the control (MFC) averaged 30.2% compared to 0% on non-target hosts. Low rate of parasitoid emergence in the laboratory (average 30.2 %), and increased rate of MFC nymphal mortality was due to adult feeding. Percent field parasitism reached up to 32.7% emergence in the NSW Alstonville, Australia. We report on the parasitoid performance in native Australia, rearing biology, host specificity testing, and the extant natural enemies associated with MFC in Hawaii. A petition to release this parasitoid for the biocontrol of MFC in Hawaii is pending. Once permitted for release, the colony will be shared with South African Mac Nut Association for their biocontrol program of this invasive pest. They will conduct their own testing before approval for release.