Although air circulators are commonly used in agricultural buildings, it is difficult to evaluate the practical performance of many such air circulators currently available in Japan. This study compares the air circulation performances of six commercial air circulators and demonstrates that the distribution of air velocity generation varied among them. Although the power consumption significantly correlated with the range of air circulation observed, the airflow rate listed in the specifications did not. Therefore, power consumption is a better evaluation indicator for the performance of air circulators under the limitation that exceedingly inefficient products are hardly distinguishable. In addition, the energy efficiency in the usage of air circulators is discussed.

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Evaluation Indicator for Greenhouse Air Circulator Performances

We report here on the development of a system for producing cruciferous vegetables without using chemical pesticides. This system enables small-scale farmers in hilly and mountainous areas in the western region of Japan to grow products of equivalent volume and quality to those produced by standard practices. The first steps in developing the system involved modifying and creating methods to protect cruciferous vegetables against insect pests. Crops were protected from flying pests, such as the white cabbage butterfly, cabbage armyworm, diamondback moth, cabbage sawfly, leafminer fly, cabbage bug, striped flea beetle, and brassica leaf beetle using a 0.6 mm mesh screen. Bacillus thuringiensis preparations, the use of which is permitted by Japanese Agricultural Standards for organic plants and organic processed foods of plant origin, were used to prevent damage caused by butterfly larvae, (white cabbage butterfly, cabbage armyworm, and diamondback moth) that hatch from eggs deposited on the outer surface of the screen through which they can invade. Invasion by crawling pests, such as the striped flea and brassica leaf beetles, was suppressed by covering the ground around the greenhouse with a mulching sheet to control weeds that form the habitat for these pests. Aphids passing through the 0.6 mm mesh screen were eliminated by a banker plant system employing the aphid parasite Diaeretiella rapae (McIntosh), a natural predator. Solarizing the soil before cultivation destroyed the pests' larvae, pupae, or eggs residing underground, such as those of the striped flea beetle and cutworm, while pest damage by vegetable weevils was prevented by inserting our newly invented traps just underground. The second step in developing the system involved dealing with higher greenhouse temperatures during summer that would result from the 0.6 mm mesh screen cover. To keep the wet bulb globe temperature (WBGT) around the worker within acceptable limits, a battery-powered ventilator consisting of a cart, fan, solar battery, and ordinary battery was used as well as installing simple roof windows, all of which effectively lowered the WBGTs. By combining these methods, we were able to demonstrate that the system was highly effective for producing quality cruciferous vegetables in greenhouses and in open fields.

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Development and Implementation of an Environmentally Conscious System for Producing Cruciferous Vegetables by Small Farms in a Hilly and Mountainous Area of Western Japan

Physical control using insect screens is expected as an alternative method to chemical control. However, insect screens with finer mesh sizes to exclude minute pests have the problem of achieving both a control effect and ventilation. We evaluated the suppressive effect of a red insect screen on a Thrips tabaci Lindeman (Thysanoptera: Thripidae) population on cabbage in 2011. The number of T. tabaci on cabbage covered with a red insect screen was significantly lower than that with a white insect screen with the same mesh size. Further investigations in 2017 and 2018 revealed that the control effect of the red insect screen was not different between 0.6- and 0.8-mm mesh sizes, and better than that of the white insect screen with a 0.4-mm mesh size. According to catching test with sticky traps, camouflage for cabbage by red insect screen is considered as possible mechanisms for the control effect. These characteristics should make it possible to achieve both ventilation and an effect to control T. tabaci on cabbage. Furthermore, early growth of cabbage seedlings was not different between covering red and white insect screen with 0.8-mm mesh size. From these results, we discuss the beneficial effects of red insect screens.

Effect of covering with red insect screen to control Thrips tabaci (Thysanoptera: Thripidae) on cabbage

Abstract Development of advanced pest control methods that do not rely on insecticides is an important issue for sustainable agriculture. Particularly with regards to micro pests that are not only highly resistant to various insecticides but also because we are running out of options for which insecticide to use against them, resulting in enormous economic damage worldwide. Here we report that the effectiveness of the conventional insect net can be greatly advanced by changing their color to red that helps significantly reduce pesticide use. We demonstrate the red effect using Onion thrips, Thrips tabaci a main vector of Iris Yellow Spot Virus (IYSV) and Tomato Spotted Wilt Virus (TSWV) that cause serious damage to various vegetables. New red nets succeeded in suppressing the invasion rates and damages (white spots on the leaves) in a Welsh onion greenhouse with minimum use of pesticides. We discuss how red nets are compatible with labor-saving, sustainable agriculture and the future potential of “optical pest control” based on insect color vision and its behavioral response. 

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T. Okada

Papers

Improvement of human thermal comfort in greenhouses with insect- proof screens