In the summer of 2019 and 2020, leaf sheath rot and concomitant outer leaf death symptoms were found on four commercial Welsh onion fields in Iwate, Japan. Nine isolates obtained from diseased plants were identified as Rhizoctonia solani anastomosis group (AG)-1 IB, AG-4 HG-I, AG-4 HG-II, AG-4 hybrid subgroup between HG-I and HG-II, AG-5, binucleate Rhizoctonia AG-A, and Waitea circinata var. zeae (Asexual morph: Rhizoctonia zeae), based on cultural morphology, temperature-dependent growth characteristics, hyphal anastomosis reaction, and genome analysis using specific PCR, and rDNA-ITS sequences. In pathogenicity tests on Welsh onion seedlings, isolates of binucleate Rhizoctonia AG-A and W. circinata var. zeae were less virulent than R. solani AG-1 and AG-4 isolates. To the best of our knowledge, this is the first report of leaf sheath rot on Welsh onion caused by binucleate Rhizoctonia AG-A and W. circinata var. zeae.

In June 2019, basal petiole rot of wasabi seedlings with withering symptom was observed in Iwate, Japan. Isolates from diseased tissues were identified as Rhizoctonia solani anastomosis group (AG)-2-1·Subset 2 and AG-2-1·clade HK on the basis of cultural morphology, temperature-dependent growth characteristics, hyphal anastomosis reactions, and DNA sequences of the rDNA-ITS region. Artificial inoculation with three isolates resulted in basal petiole rot and withering of wasabi seedlings. The occurrence of damping-off on wasabi caused by R. solani has been reported in Japan (Suzuki, 1976); however, details of AG and locations were not clarified. Since the AGs of R. solani causing this damping-off were initially found in Japan, we propose to the inclusion of R. solani AG-2-1·Subset 2 and AG-2-1·clade HK as one of the pathogens of the disease.

In June 2016, basal stem rot and underdeveloped broccoli growth occurred in two fields in Hokkaido, Japan. Two isolates obtained from diseased broccoli were identified as Rhizoctonia solani (anastomosis group) AG-2-1·Subset 1 and AG-2-2 IV on the basis of morphology of the cultured samples, temperature-dependent growth characteristics, hyphal anastomosis reactions, and result of PCR analysis with specific primers. In Japan, damping-off on young broccoli plants caused by Rhizoctonia solani AG-1 IC, AG-2-1·Subset 2, AG-2-2 IIIB, AG-4 HG-I, and foot rot of matured broccoli caused by R. solani AG-2-2 IV has been previously reported. We investigated the pathogenicity of the two isolates using three different growth stages of broccoli plants (3-week-old, 8-week-old, and 3-month-old). Inoculated 3-week-old and 8-week-old broccoli developed severe wilt. However, inoculated 3-month-old matured broccoli showed only basal stem rot without wilt symptoms. The observed symptoms and pathogenicity were coincident with that of the damping-off on broccoli. This is the first report of damping-off on broccoli caused by R. solani AG-2-1·Subset 1 and AG-2-2 IV in Japan.

From 2009 to 2017, a total of 10 isolates of Rhizoctonia-like fungi were obtained from various crops in Hokkaido, Japan. These isolates were identified based on number of nuclei per cell, hyphal diameter, culture appearance and sequences of the rDNA-ITS region. Five isolates obtained from diseased strawberry bud, tuberous root of yacon, basal petiole of potherb mustard, basal stem of alstroemeria and bulb of lily were binucleate Rhizoctonia AG-A. Two isolates obtained from leaf sheath of wheat were binucleate Rhizoctonia AG-DI. Two isolates obtained from Chinese yam root and leaf sheath of barley were binucleate Rhizoctonia AG-U. One isolate obtained from black oat leaf was Waitea circinata variety zeae. These results provide useful information on the diagnosis of crop diseases caused by Rhizoctonia spp.

The rice bug, Leptocorisa chinensis (Hemiptera: Alydidae),is distributed from south-western to eastern Japan. Recently, its northern limit has been expanding to Iwate Prefecture, Tohoku district. The distribution areas of this species may be closely associated with the temperature during the peak of winter. Two types of estimation method for describing the distribution areas based on the winter temperature were reported in Miyagi and Fukushima Prefectures. Those two methods were applied in estimating the potential distribution areas in eastern Japan other than Miyagi and Fukushima Prefectures. The prediction accuracy was evaluated using a receiver operating characteristic curve. Though the temperature threshold for predicting the existence of L. chinensis requires a more detailed study, these two estimation methods may be used for predicting the existence of this species in eastern Japan.

Helicoverpa armigera is a major food-crop and vegetable pest. Severe damage of soybean by the species has been observed in Miyagi Prefecture. It is difficult to distinguish the early-middle instar larvae of H. armigera from those of Heliothis martima, usually present on soybean; thus, an identification method for the larvae was developed using their morphology and standard DNA barcoding. Therefore, distinguishing their first and second instar larvae was morphologically challenging; however, their third instar larvae were distinguished using the base of D1 setae on the abdominal segments, especially in A1 and A8 of H. armigera, which is large and conically protruded. In contrast, the base of H. maritima is small and almost flat. Finally, their larvae were distinguished by standard DNA barcoding (a part of mt COI [cytochrome c oxidase I] region).

Kudzu (Pueraria montana var. lobate) is an Asian plant, which is also present in other countries and has become problematic. Attempts at the biological control of kudzu have been unsuccessful because of its unclear relationship with other species. This study examined the effects of a native leaf beetle (Pagria ussuriensis) on kudzu in Japan. It was revealed that P. ussuriensis damages kudzu leaves on the lower half of the stem, thus reducing plant water content. Furthermore, the feeding pattern of P. ussuriensis depends on the trichome density of kudzu leaves.

Further study is needed to clarify whether P. ussuriensis functions as a biopesticide or is a pest of cultivated legumes.

In “Catalogue of the insects of Japan, Volume 4 Paraneoptera” published in 2016, Hokkaido was excluded in the distributions of two aphid species, Lipaphis erysimi and Semiaphis heraclei. However, the literature and field surveys in this report revealed that both species are distributed in Hokkaido. Furthermore, in the field survey, the oviparous females of L. erysimi were recorded from Hokkaido for the first time, implying that the species overwinter in eggs in Hokkaido. Additionally, Aegopodium podagraria and Angelica edulis were recorded as the host plants for S. heraclei for the first time in the world.

Population dynamics of alate aphids were surveyed using yellow pan traps at two garlic fields (Pippu and Takikawa) in Hokkaido, Japan, in 2020. In the Pippu survey during the early spring to harvest season, the first capture of alate aphids was observed on May 28. In Takikawa during the same season, the first capture was observed from May 30 to June 4. Additionally, in Pippu, during the planting time to snow coverage, the last capture was observed from October 30 to November 1.