Risk of infestation and damage to subalpine Abies trees by the curculionid leaf-mining pest Parendaeus abietinus

The curculionid leaf-mining insect Parendaeus abietinus causes defoliation and death of firs (Abies spp.) via adult feeding on needles and larval mining on current-year needles. Its primary hosts are A. firma and A. homolepis, which are distributed in moderate to lower subalpine elevations in Japan. This weevil has had two outbreaks; the second, in 2019, took place in a planted Abies forest in Iwate Prefecture, where the weevil’s distribution then expanded northward beyond the natural range of these firs. There is a risk that P. abietinus will expand to higher altitudes and latitudes, where it may cause severe damage to subalpine Abies species that have not previously been recorded as host plants. In Japan, the three subalpine Abies species not previously recorded as hosts are A. mariesii, A. veitchii, and A. sachalinensis. Notably, A. sachalinensis is an economically important species in Hokkaido, and weevil infestation there would pose a serious problem. Therefore, in this study, I investigated the ability of P. abietinus to utilize these unrecorded Abies trees by rearing adult weevils on them and examining needle feeding and survival. The results showed that P. abietinus adults fed on A. veitchii but not on A. sachalinensis, and consequently, they survived on A. veitchii as well as on A. homolepis. Comparison of the needle shape and size among the plant species indicates that these needle characteristics were not responsible for P. abietinus adults’ feeding behavior.