Behaviorally based research initiatives on macadamia nut insect pests in Hawaii

Macadamia is an important agricultural commodity in Hawaii with an average of ~$51 M in farm value in the past five years. Among the serious threats to macadamia production in Hawaii are losses due to infestations by the tropical nut borer (TNB) (Coleoptera: Curculionidae) and Cryptophlebia moths (Lepidoptera: Tortricidae). In 2019, 5.8 % and 18.6 % of harvested nuts were culled due to TNB and Cryptophlebia attacks, respectively, amounting to an estimated loss of $ 3.8 M. The TNB is a beetle species that attacks mature macadamia nuts, with higher infestations on nuts that have already fallen to the ground and are ready for harvesting. While infestations by Cryptophlebia moths are prevalent on developing immature nuts still attached to trees. Apart from direct nut sampling which is labor-intensive and time-consuming, there are no other options available for growers to monitor TNBs. Current management of these beetles is also limited to cultural control such as removal of infested nuts and/or frequent harvesting of nuts which can be impractical for larger operations. On the other hand, although Cryptophlebia moths (C. illepida and C. ombrodelta) are known to respond to sex pheromone, monitoring of these moths using pheromone-baited traps needs more refinement. In addition, no current management strategies against these moths are available for macadamia growers. Recent research efforts investigating the behavior and ecology of these two key pests of macadamia in Hawaii are presented, and the implications of the results to the development of pest management strategies are discussed.