In 2022, mass yellowing of Cycas revoluta leaves caused by a scale occurred on Amami-Oshima Island. We identified the scale as Aulacaspis yasumatsui, a worldwide cycad pest. The occurrence was reported as the first record of the A. yasumatsui in Japan. In this paper, we report on the identification details and the survey on the distribution and damage in the Amami Islands. We identified the scale based on its morphological characteristics and then confirmed the identification based on its nucleotide sequences of COI and COII regions of mitochondrial DNA. The nucleotide sequence of COI barcode region (630 bp) in our sample from Amami-Oshima Island is 100% identical to that from Fujian Province in China previously reported. The scale was found in Amami City, Tatsugo Town, Yamato Village and Uken Village. In C. revoluta, where this scale occurs, the leaves ranged from those with no yellowing to those with all leaves yellowed. Severe damage, such as yellowing of all the leaves, and mass yellowing was concentrated in near the Naze Port in Amami City.

Ips subelongatus is the most important pest affecting larch plantations. Despite proper thinning treatments, damages caused by I. subelongatus have been reported in Hokkaido. Thinning is effective in preventing damage by scolytid beetles as it enables larches to allocate sufficient photosynthates for the production of preventative substances, and also it enhances root system development to prevent fine roots from being damaged by tree swaying. However, after thinning, more sunlight penetrates into a stand, and air turbulence is increased, which could cause water deficiency in larches, and render them susceptible to I. subelongatus. Herein, thinning methods that would make larch plantations more resistant to I. subelongatus-induced damages are recommended, such as trees that are suppressed, non-vigorous, inclined, having a broken stem, damaged by insects, or diseased must be harvested; selection thinning should be practiced rather than row thinning; heavy or row thinning should be practiced only in young stands if they are planned; and light thinning is recommended in overstocked stands.