Katsumi Ohyama

Necessity and Concept of the Closed Transplant Production System

We are requested to develop a concept, a methodology and an industry to solve the global issues on environmental pollution and shortages of food, feed, phytomass (plant biomass) and natural resources including fossil fuels and usable water. These issues are considered to become more and more serious on a larger scale in the forthcoming decades. In order to solve those issues in the 21st Century, billions of plants are required every year not only for food, feed and environment conservation, but also for alternative raw materials to produce energy, bio-degradable plastics and many other industrial products. By using plant-derived products, we can minimize the environmental pollution and the use of fossil fuels and atomic power. Then, we need billions of quality transplants (small plants) every year to be grown in the fields with maximum use of solar energy and minimum use of resources under harsh environmental conditions. These quality transplants can be produced only under carefully controlled environments. Bioengineering is expected to provide a useful concept and a methodology to develop the bioindustry for solving the above global issues substantially. In bioengineering, the global and local flows of energy, mass (or materials) and information are analyzed with special attention to the organic and inorganic metabolisms of plants, animals including humans and microorganisms. Concept of ‘closed-type or closed production systems’ is essential to develop a production system with minimum use of resources and with minimum environmental pollution. This concept can be applied to develop a closed-type transplant production system with artificial lighting for producing billions of quality transplants with minimum use of resources and with minimum environmental pollution. Research and development of the closed transplant production systems will create a new field of bioengineering and bioindustry.

An LED-based UV-B irradiation system for tiny organisms: System description and demonstration experiment to determine the hatchability of eggs from four Tetranychus spider mite species from Okinawa.

We developed a computer-based system for controlling the photoperiod and irradiance of UV-B and white light from a 5×5 light-emitting diode (LED) matrix (100×100mm). In this system, the LED matrix was installed in each of four irradiation boxes and controlled by pulse-width modulators so that each box can independently emit UV-B and white light at irradiances of up to 1.5 and 4.0Wm(-2), respectively, or a combination of both light types. We used this system to examine the hatchabilities of the eggs of four Tetranychus spider mite species (T. urticae, T. kanzawai, T. piercei and T. okinawanus) collected from Okinawa Island under UV-B irradiation alone or simultaneous irradiation with white light for 12hd(-1) at 25°C. Although no eggs of any species hatched under the UV-B irradiation, even when the irradiance was as low as 0.02Wm(-2), the hatchabilities increased to >90% under simultaneous irradiation with 4.0Wm(-2) white light. At 0.06Wm(-2) UV-B, T. okinawanus eggs hatched (15% hatchability) under simultaneous irradiation with white light, whereas other species showed hatchabilities <1%. These results suggest that photolyases activated by white light may reduce UV-B-induced DNA damage in spider mite eggs and that the greater UV-B tolerance of T. okinawanus may explain its dominance on plants in seashore environments, which have a higher risk of exposure to reflected UV-B even on the undersurface of leaves. Our system will be useful for further examination of photophysiological responses of tiny organisms because of its ability to precisely control radiation conditions.

Air temperature optimisation for humidity‐controlled cold storage of the predatory mites Neoseiulus californicus and Phytoseiulus persimilis (Acari: Phytoseiidae)

BACKGROUND Humidity-controlled cold storage, in which the water vapour pressure is saturated, can prolong the survival of the predatory mites Neoseiulus californicus (McGregor) and Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae). However, information on the optimum air temperature for long-term storage by this method is limited. The authors evaluated the survival of mated adult females of N. californicus and P. persimilis at 5.0, 7.5, 10.0 and 12.5 °C under saturated water vapour condition (vapour pressure deficit 0.0 kPa). RESULTS N. californicus showed a longer survival time than P. persimilis at all the air temperatures. The longest mean survival time of N. californicus was 11 weeks at 7.5 °C, whereas that of P. persimilis was 8 weeks at 5.0 °C. After storage at 7.5 °C for 8 weeks, no negative effect on post-storage oviposition was observed in N. californicus, whereas the oviposition of P. persimilis stored at 5.0 °C for 8 weeks was significantly reduced. CONCLUSION The interspecific variation in the response of these predators to low air temperature might be attributed to their natural habitat and energy requirements. These results may be useful for the long-term storage of these predators, which is required for cost-effective biological control.

Humidity‐controlled cold storage of Neoseiulus californicus (Acari: Phytoseiidae): effects on male survival and reproductive ability

Humidification can suppress water loss from an organism and has great potential for improving the cold storage of short‐lived arthropods, such as predatory mites. The effectiveness of humidity‐controlled cold storage was recently verified for Neoseiulus californicus (McGregor) females but was not examined for males. Combining both males and females in one storage protocol might increase the predator population because it would enhance the opportunity for multiple mating, which is necessary for females to maximize their egg production. Newly emerged adult males were stored at an air temperature of 5°C and relative humidity (RH) of 100% or 80%. The median survival time (LT50) was 32 days at 100% RH and 14 days at 80% RH; the survival curves differed significantly. Males stored at 100% RH for 0, 10, 20 and 30 days were introduced to virgin females for mating at 25°C to evaluate their reproductive ability. The pre‐oviposition period was significantly prolonged in the females mated with males stored for ≥20 days. No negative effects of storage were observed on the oviposition period, total number of eggs or net reproduction rate (R0) in the females mated with males stored for ≤20 days or on the mean generation time (T) for those stored for 30 days. A slight decrease in the intrinsic rate of increase (rm) was observed in the females mated with males stored for ≥20 days. Our storage method can preserve N. californicus males for 20 days with only a minor reduction in their survival and reproductive ability.

Night-interrupting light inhibits diapause induction in the Kanzawa spider mite, Tetranychus kanzawai Kishida (Acari: Tetranychidae).

The inhibitory effects of the timing, intensity (I(I)) and period (I(T)) of night-interrupting light on diapause induction of the Kanzawa spider mite (Tetranychus kanzawai) were investigated in a series of laboratory experiments. During a light and dark period of 8 and 16 h d(-1), respectively, a single 1-h night-interrupting light was applied at early (E), middle (M), and late (L) parts of the dark period: i.e., at 3, 7.5, and 12h after the start of the dark period, respectively. No interrupting light was applied in the control treatment. The incidence of diapause was significantly lower in the M treatment (63%) compared to the control treatment (100%). In the E and L treatments, more than 90% of females entered diapause, which was comparable to the control treatment. Since the longest consecutive dark period during the E and L treatments was longer than the critical dark period (CDP) of 10.5-11 hd(-1), during which 50% of females entered diapause, the night-interrupting light probably failed to prevent diapause induction. However, in the M treatment, the longest consecutive dark period was shorter than the CDP; therefore, the night-interrupting light inhibited diapause induction. Moreover, the inhibitory effects of night-interrupting light in the M treatment increased as I(I) and I(T) increased. The dose of night-interrupting light (I(I)×I(T)) was significantly negatively related to the incidence of diapause. The median effective dose for 50% disturbance of diapause induction was 2.5 kJ m(-2) at wavelengths between 350 and 1050 nm. Our results suggest that the longest consecutive dark period and the dose of night-interrupting light should both be considered when a lighting-based physical control is applied to inhibit diapause induction and consequent overwintering of T. kanzawai in commercial agricultural fields.

An improved space-saving system for testing photoperiodic responses of insects and mites: its use for diapause experiments in the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

We developed an improved space-saving system consisting of a netbook computer, microcontrollers, aluminum bottles with white light-emitting diodes (LEDs), and an incubator. In this system, light and dark periods, light intensity, and night-interrupting light conditions (i.e., period, intensity, and timing) can be independently controlled in each bottle with a pulse-width modulator (PWM). Scheduled photoperiodic conditions with less fluctuation in air temperature were successfully realized with this system. Night-interrupting light conditions that may prevent diapause induction and subsequent overwintering were examined using this system to establish a novel strategy for nonchemical control of the two-spotted spider mite, Tetranychus urticae Koch. The results show that diapause incidence decreased as the cumulative intensity of night-interrupting light increased. Taken together, data show that this system can provide an accurate and space-efficient means of investigating the photoperiodic responses of insects and mites without unwanted fluctuations in air temperature, thus contributing to development of a lighting-based pest-control method in commercial agricultural fields.

Anoxia treatment for selectively controlling spider mites Tetranychus urticae and Panonychus citri with little impact on the predatory mite Neoseiulus californicus

ABSTRACT Anoxia treatment with a deoxidant consisting of iron, calcium chloride and silicon dioxide was evaluated at different temperatures for pest spider mites (Tetranychus urticae and Panonychus citri) and their natural enemy, the predatory mite Neoseiulus californicus. No spider mite eggs survived when exposed to anoxia for 18 h at 20°C or for 12 h at 25°C, whereas the survival of N. californicus eggs under these conditions was 53% and 72%, respectively. No adult female spider mites survived when exposed to anoxia for 15 h at 20°C or for 8 h at 25°C, whereas >95% of adult N. californicus females survived under these conditions. These results indicate that anoxia has potential as a selective method for controlling pest mites, such as T. urticae and P. citri, but has little impact on their natural enemy, N. californicus.

Reductions in Energy Consumption and CO2 Emissions for Greenhouses Heated with Heat Pumps

In the greenhouse industry, it is essential to use energy efficiently by operating economically feasible heating systems instead of the traditional combustion-based heating systems. In our experiment, a heating system with household heat pumps was operated at nighttime. Another heating system with a kerosene heater was used as a comparison. We compared the energy consumption, energy utilization efficiency, CO2 emissions and energy costs of two heating systems. When the inside air temperature was maintained at around 16°C while the outside air temperature ranged between -5°C and 6°C, the results showed that 1) the energy consumption was 25% to 65% lower in the greenhouse with heat pumps (Ghp) when compared to the greenhouse with a kerosene heater (Gkh), 2) the energy utilization efficiency of the heat pumps was 1.3 to 2.6 times higher than that of the kerosene heater, 3) CO2 emissions were reduced by 56% to 79% in the Ghp when compared to the Gkh, and 4) energy cost was lower in the Ghp when compared to the Gkh. These results indicate that the heat pump system is found more efficient than the kerosene heating system and economically feasible for greenhouse heating.

A PRECISE IRRIGATION SYSTEM WITH AN ARRAY OF NOZZLES FOR PLUG TRANSPLANT PRODUCTION

A precise irrigation system with a 6 × 12 array of needle-like nozzles was developed for plug transplant production using 72-cell plug trays. When a command for irrigation is given to the system, all of the nozzles are directly inserted into the corresponding cells at the same time to discharge a predetermined amount of water or nutrient solution. The amount of irrigated water from each nozzle (Q) can be controlled by adjusting the discharge time to keep the solenoid valve open (T) and by discharge pressure (P). The objectives of the present study were: (1) to obtain quantitative data for the control of Q, and (2) to examine the performance of the system during a plug transplant production period of 20 days. By adjusting T of each nozzle individually and P, a uniform distribution of Q was achieved over the tray. Consequently, a high value of Christiansen coefficient of uniformity was obtained (97.2% to 98.4%). During the plug transplant production period, the volumetric water content in each cell could be controlled by using the system without any growth deterioration of the transplants owing to the root damage caused by the nozzle insertion into the substrate. These results demonstrate that this system is feasible for precise irrigation management of plug transplant production.

Evaluating Labor Productivity in a Plant Production System with Sole-source Lighting: A Case Study

Labor productivity in terms of material value (weight of plants harvested per hour per person) was evaluated for 6 months from the start of operations in a research facility at Osaka Prefecture University (Osaka, Japan), serving as a model system for plant production with sole-source lighting (also referred to as a ‘‘vertical farm’’ or ‘‘plant factory’’). The research facility is capable of producing lettuce plants (Lactuca sativa) at a maximum production rate of 5000 plants/day when the relative harvest rate (i.e., number of plants harvested/maximum potential number of plants harvested) is 100%.However, in the present study, the relative harvest rate at the research facility was in the range of 17% to 65% and labor productivity varied from 1.5 to 6.0 kg h per person. The evaluation results indicated that increasing the weight of plants harvested and increasing the relative harvest rate was necessary to maintain a high level of labor productivity. The processing time for harvesting was greatest among all plant operations, suggesting the need to reduce the time taken in this operation to increase the labor productivity in the research facility and in other plant production systems with sole-source lighting (PPSLs). This study demonstrates the importance of analyzing labor productivity for increasing the commercial feasibility of PPSLs. However, further long-term investigation with higher relative harvest rates is required for a more definitive conclusion.