To prevent potato storage rot caused by Phytophthora infestans, we developed a novel chemical control method wherein a fungicide is applied to foliar residue in blighted potato fields. We applied cyazofamid to inoculated residue and sampled the ridgetop soil 7 days later. The population density of P. infestans in sampled soil was quantified using real-time PCR. To evaluate the inoculum potential of each soil, sampled soil was mixed with injured healthy tubers and incubated for 3 weeks. After incubation, the number of rotten tubers was counted. In most experiments, the quantity of P. infestans DNA and number of rotten tubers both decreased with use of proposed method. These results imply that the proposed method may prevent potato storage rot.

In March 2018, bud rot and basal petiole rot of strawberry were found in Hokkaido, Japan. An isolate obtained from the diseased tissue was identified as Rhizoctonia solani anastomosis group (AG)-2-1・Subset3 (AG-2-1/Nt) based on the anastomosis reaction, culture appearance, temperature-dependent growth characteristics, specific PCR, and DNA sequences of the rDNA-ITS region. Original symptoms were reproduced on inoculated plants with the isolate. This is the first report of strawberry bud rot caused by R. solani AG-2-1・Subset3 in Japan; therefore, we propose its inclusion as one of the pathogens of the disease.

The rice bug, Leptocorisa chinensis (Hemiptera: Alydidae), was first recorded in Rikuzentakata, Iwate Prefecture, Japan, in 2019. This species has a known distribution in southern Japan, and its northern limit was previously reported to be almost 100 km south of the new record. We investigated the current distribution status, crop damage, and potential overwintering area for the species. We captured individuals of L. chinensis in 6 of 11 sites examined in 2019. These sites were considerably close to evergreen coniferous forests, which is the overwintering habitat of this species. Pecky rice damage by L. chinensis was observed at all of the sites examined in 2018 (n=3) and 9 of the 11 sites in 2019, suggesting that adults had invaded paddy fields in nearly all of the research areas. The damage was almost 1/10 compared with that caused by other major pecky rice bugs (e.g., Stenotus rubrovittatus), and no serious damage caused by L. chinensis was observed. The mapping of previous winter temperature data shows that the potential overwintering area of this species has been gradually expanding, which highlights the need for further investigation of its distribution.

In the onion fields of Hokkaido, a major northernmost island of Japan, outbreaks of stone leek leafminer (Liriomyza chinensis) infestation have been occurring since 2013. In fields where heavy leaf damage occurred, a proportion of the harvested bulbs showed damage from larval mines, in addition to evidence of larval remains. The capture rate of adults in yellow sticky traps indicated that leafminers produce three generations annually. The peaks include the hibernating generation (late May to early June), first generation (mid-July to late July), and second generation (mid-August to late August). The position of the damaged scales and the timing of leaf emergence indicated that bulb damage from oviposition occurred after mid-June.However, the most effective time to implement control measures against larval invasion was in early August,when two applications of effective insecticide reduced onion damage by 1/10.

Bioassays were conducted to assess the efficacy of 11 acaricides against 12 populations of two-spotted spider mite, Tetranychus urticae, collected from apple orchards in the central and southern Miyagi prefecture. Milbemectin, BPPS, acequinocyl and bifenazate, which were used infrequently in the last 10 years, showed high efficiency in all or most populations. The efficiency of cyenopyrafen and cyflumetofen, which were frequently used in most orchards are classified as IRAC code 25A, was reduced in multiple populations. Spiromesifen, which was also frequently used, showed high efficiency in most populations but reduced efficiency in some populations. This indicated that some precautionary measures, such as biennial application, need to be taken to delay the reduction of acaricides susceptibility. Surveys of the surrounding environment indicated that the orchards where many acaricides showed a higher efficiency tend to be surrounded by forest.

Bioassays were carried out to examine the susceptibility of hawthorn spider mites, Amphitetranychus viennensis to insecticides and acaricides. The eggs and adult females that originated from a population in a commercial apple orchard in Aomori Prefecture, were highly susceptible to pyrethroids, acaricides, flufenoxuron and spinetoram, while they were less susceptible to organophosphates, diamides, neonicotinoids, BTs, flonicamid, ethiprole, pyrifluquinazon and IGRs excluding flufenoxuron, in the bioassays conducted in 2019.

Considering the above results and temporal trends in the insecticides used in apple orchards, the recent increase of hawthorn spider mite in apple orchards under pest control may be due to the decreased susceptibility to organophosphates and the frequent use of insecticides that do not effectively to hawthorn spider mite.

Synthetic Grapholita dimorpha sex pheromone traps were settled in an apple/cherry orchard in Naganuma, central Hokkaido, between the summers of 2017 and 2019. Examinations of male genitalia of all the trapped Grapholita moths revealed that two congeneric species other than G. dimorpha were also trapped, i.e., G. inopinata and G. andabatana. G. dimorpha moths were trapped continuously during late May and early/middle September, with the peak period of each generation as follows; Hibernating generation: late May to early June, first generation: late July to early August, and second generation: late August. Among a total of 44 G. inopinata moths trapped, 43 were trapped between late June and late July, with only one exception caught between 21 and 25 May, 2019. A total of eighteen G. andabatana moths were trapped between late June and late July.

To investigate seasonal capturing prevalence of fruit-spotting bugs in northern Japan and to examine capturing characteristics of pheromone-baited waterless pyramidal traps, we carried out a seven-year field study at Morioka City, Iwate Prefecture, in northern Japan. We also carried out an eight-year study at Tsukuba City, Ibaraki Prefecture, in central Japan. At Morioka, Plautia stali showed prevalence with two peaks of adults and one peak of nymphs, Halyomorpha halys showed almost no capture except for one peak of adults in autumn, whereas Glaucias subpunctatus was not captured at all. At Tsukuba, P. stali was captured throughout the seasons but especially in summer. H. halys showed prevalence with two peaks in spring and autumn, and G. subpanctatus was captured only in late autumn. These results reflect the environment of each site, including weather and food distribution at local and/or landscape levels.