Spatiotemporal trends of two tortricid pests of macadamia in Hawaii unravel the threats of invasive species to native compositions

Cryptophlebia ombrodelta (Lower) and Cryptophlebia illepida (Butler) (Lepidoptera: Tortricidae) are major pests of macadamia in Hawaii, causing premature nut drop. Cryptophlebia illepida is native to Hawaii, while C. ombrodelta is an invasive pest from Australia. Due to their similar phylogeny, phenology, and damage to macadamia nuts, their populations and damage are frequently lumped. Studies in the 1990s and early 2000s showed populations of C. illepida to be four to five times over C. ombrodelta in macadamia orchards in Hawaii. However, no new studies have re-evaluated the population density of each species. Therefore, we conducted monitoring surveys at two (Keaau and Kapaau) major macadamia-producing areas in Hawaii. At both study sites, four replicates each consisting of two white Delta traps with two lures: PHEROCON Macadamia Nut Borer (MNB) and Oriental Fruit Moth (OFM) (Trecé Inc, OK, USA), and a control trap were set-up at the interior and exterior, and monitored bi-weekly for six months in 2022 and 2023, respectively. To validate the trapping data, 30 tree nuts and ground nuts (i.e., nuts that had dropped to the ground) each were collected from six trees at the exterior and interior of the orchards. Nuts were processed in the laboratory, and the larvae found in each nut was subjected to DNA extraction and sequencing. Results (i.e., the monitoring traps and DNA sequences) showed ~95% of the moths from both sites was C. ombrodelta. This implies that C. ombrodelta is a serious invasive pest that can reduce native species compositions in its invaded range.