Population density decline of a native tortricid pest, Cryptophlebia illepida , shows links to the success of an invasive congener in Hawaiian macadamia orchards

The macadamia nut borer, Cryptophlebia ombrodelta (Lower), is an invasive pest of macadamia, Macadamia integrifolia (Maiden & Betche) ( Proteaceae ), in Hawaii, and its oviposition preference and damage to macadamia nuts are similar to those of a native relative, the koa seedworm, Cryptophlebia illepida (Butler). Because of their similarities and previous studies indicating C. illepida as the dominant of the two species in macadamia orchards in Hawaii, the damage to macadamia nuts caused by Cryptophlebia moths has been categorised historically as C. illepida . However, increasing nut damage by these pests warranted new investigations into their population densities. To determine the relative abundance of the two species, two commercial macadamia‐producing areas on Hawaii Island, Keaau and Kapaau, were selected, and white‐coloured PHEROCON VI Delta traps were baited with two commercial lures: PHEROCON oriental fruit moth L2 lure and PHEROCON macadamia nut borer lure (Trécé, Inc.), and were placed at the exterior and interior of the orchards in a randomised complete block design. Traps were serviced bi‐weekly from May to October in 2022 and 2023, and concurrently, developing nuts on the trees and harvestable nuts from the ground were collected and assessed for larvae of both pests. Moth captures were examined under a stereomicroscope, and larvae were subjected to mitochondrial CO1 gene DNA sequencing. Results showed that C. ombrodelta (91%) was significantly more abundant than C. illepida (9%). This implies that, contrary to historical reports, C. ombrodelta has surpassed the population of C. illepida in macadamia orchards in Hawaii. Therefore, management strategies should be directed specifically to C. ombrodelta to reduce impacts on nut productivity.