Rice bugs, the most significant pests in rice cultivation, have been a persistent problem for over two decades in the Tohoku region and throughout Japan. One of the major pest species, Stenotus rubrovittatus, has been expanding its area of damage along the Sea of Japan in the Tohoku region since the mid-2000s. Additionally, Leptocorisa chinensis has been expanding its distributing area along the Pacific coast in the Tohoku region since the late 2010s due to climate change. Consequently, the potential for rice bug damage remains high, and paying close attention to their occurrence and damage is essential. In order to understand the future needs for rice bug management research, a regional survey was conducted from 2014 to 2021 by six prefectural agricultural experiment stations in the Tohoku Region and the NARO Tohoku Agricultural Research Center. The survey reviewed the transition of the major rice bug species and management techniques during this period, as well as the damage caused by rice bugs throughout Japan since the late-1990s when rice bugs first emerged as a significant pest in rice cultivation. We also overviewed their damage, the number of issued warnings and advisories for the rice bugs throughout Japan, and newly developed monitoring methods. The factors enhancing the rice bug damage and its management techniques were also discussed.

View full abstract

The monitoring of the growth of crops in large-scale cultivation has relied on manual measurements of plant height which is not only labour intensive but is also cumbersome. As an alternative, we proposed the utilisation of remote sensing techniques involving taking aerial images using Unmanned Aerial Vehicle (UAV) and it’s processing thereof. To process these images, a photogrammetric technique SfM (Structure from Motion) which involves estimating the three-dimensional structure from the multiple images obtained is utilised. However, to improve the accuracy of SfM it is imperative to properly position ground control points (GCPs) when taking images in the field. The placement of GCPs on the field is limited in large-scale cultivation where the entire field is covered by crops, especially inside the field as this would have negative impact on the uniformity of the crops and thus affecting the successive growth season. Our results indicated that by placing the GCPs at the edges of the field, i.e., at the corners and in between the corners, a total of 8 GCPs, we could precisely estimate the crop height, similarly to when more GCPs were placed inside the field. Since the UAV flight time is inversely proportional to the square of the flight altitude, a higher altitude would require less time, but result in lower spatial resolution. As a proof of concept, a flight altitude of 50 m was sufficient to obtain images of a 4-ha field with 8 GCPs on the edges of the field with high accuracy. These results indicated that UAVs combined with only GCPs on the edge of the field can be utilised to estimate with high precision the growth of crops in large-scale thus labour saving.

View full abstract

In recent years, the formation of large-scale rice-vegetable paddy farming complexes has become an issue in Hokkaido. In this context, the Southern Hokkaido Area, where this complex management is being developed, has attracted attention. In this paper, we examine the agricultural structure of the Southern Hokkaido Area and clarify the conditions for the existence of large-scale paddy farming complexes. The results are summarized as follows. First, in the Southern Hokkaido Area, （1） the liquidation of leased land is progressing and the scale of management is expanding, and （2） the weight of vegetable cultivation is high. （3） The Iburi region area is a representative area for the development of combined rice and vegetable farming. Second, the conditions for the existence of large-scale paddy farming complexes in X town in the Iburi region area: （1） Employed several permanent workers for open field vegetable crops., and （2） large-area farmland were formed for each paddy rice and open-air vegetable crop under employment-type corporate management.

View full abstract

‘Natsunoshizuku’ is a new strawberry cultivar (Fragaria × ananassa Duch.), that originated from a cross between ‘Miyazaki-natsuharuka’ and 06sAB-4e (‘Natsuakari’ × Morioka30) in 2011. This cultivar shows upright plant shape, is very vigorous, and produces many runners. ‘Natsunoshizuku’ is everbearing and can bear fruits in summer and autumn, which are off-crop season of strawberry in Japan. The marketable yield of the cultivar is more than other everbearing cultivars ‘Natsuakari’ and ‘Summer-berry’ and expected to exceed 3 t / 10a in regions with cool summers. The averaged marketable fruit weight throughout the harvest period is about the same as ‘Natsuakari’ and ‘Summer-berry’, around 10g. The shape, skin color and flesh color of its fruit is conical, medium red, and light red, respectively. Achenes are at the same level as the pericarp. Sticking out of achenes on the surface of a fruit, which often lowers the value of the fruit, is unlikely occur. Fruit firmness, which is relevant to ease of transportation and shelf life, is higher than ‘Natsuakari’ and ‘Summer-berry’, making it suitable for commercial use during summer and autumn. Both soluble solids and acidity of the fruit are high, making it suitable for cakes and other desserts.

View full abstract

The vibrational behavior of the brown winged green stink bug, Plautia stali, a harmful orchard pest, was investigated. It was confirmed for the first time that unmated adult females and males of this species exhibit oscillatory behavior. Notably, we observed that adult females frequently vibrated their abdomens vertically（ oscillatory behavior）. Furthermore, the pulse length of the vibration was approximately 0.18 seconds, acceleration was approximately 0.16 m/s². Dominant frequency was 150 Hz, and RMS value （root mean square of acceleration at dominant frequency） was 0.006 m/s². The vibration frequency of abdominal movement calculated from video analysis was 7.5 times per second, and the amplitude was about 0.077 mm. These results suggest that adult stink bugs use vibration for communication between males and females, as well as between other individuals, indicating the potential use of artificial vibrations for behavior control.

View full abstract

Reduction of respiration is a storage technique for preserving the quality of fruits and vegetables as it suppresses various metabolic activities. In the present study, the effects of low oxygen environment on respiration rate of nine cut flowers, including ring-flowered chrysanthemum, small-flowered chrysanthemum, rose, carnation, lisianthus, two gentian varieties （Gentiana scabra and Gentiana triflora）, lily, and tulip, were investigated to develop the storage technique of cut flowers. Respiration rate at normal ambient air was compared to that at reduced concentrations of oxygen. Significant differences in respiration rate were observed at ≦ 10% oxygen in ring- and small-flowered chrysanthemums, G. scabra and lily, and ≦ 5% oxygen in lisianthus, G. triflora and tulip. However, there were no significant differences in respiration rate in rose and carnation even at 2% oxygen. These results indicate that effective use of oxygen concentration to reduce respiration rate depends on the kind of cut flowers.

View full abstract