We established a soybean banker plant system and evaluated the biological control effects of aphid control in bell pepper greenhouses. The soybean banker plant was B.communis breeding system and developed as an alternative aphid control agent to the most common Barley banker(Barley-Colemani). After inoculating approximately 50 soybean aphids(Aphis glycines, aphid starter population) on 2 week old soybean seedling pot after sowing and then releasing aphid parasitoids, an average of 348.7 parasitic wasps per a soybean banker plant could be produced without additional host aphid inoculation. Common recommendation for installation in the greenhouses are about 2 soybean banker plants per 330㎡ before or immediately after planting. If the number of aphids per stem is fewer than three on 2 weeks after installation of the banker plant, additional supplementation of 20~30 aphids is necessary to maintain this system for one month. When one soybean banker plant was installed per 120㎡, the aphid control effect was about 60% on the 21st day after installation.
Terrestrial toxic effects of soil arsenate were studied using a model system consisting of Capsicum annum, Myzus persicae, Aphidus colemani. We investigated the transfer of arsenic from soil to aphid and toxic effect of elevated arsenic on each trophic level. Artificial soil was treated with arsenate at 0, 2 and 6 mg/kg, then arsenic concentration of soil, plant tissues (root, stem, leaf) aphids were measured to observe the arsenic transfer. Toxic effects of elevated arsenic concentrations on each species were investigated at population level. Physiological and biochemical responses of plant and aphid were observed. In addition, enzyme activities against reactive oxygen species (ROS) induced by arsenic stress were also investigated. Host choice capacity and parasitism success of the parasitoids were examined. The results suggest that arsenic concentration in plant tissues and aphids were elevated with increased concentration of arsenic in soils. Physiological responses of plants were not affected by soil arsenic but there was change of biochemical responses. Decreased fecundity and honeydew excretion of aphids were observed, elevated activity of antioxidant enzymes indicated that aphids received the ROS stress induced by arsenic. Decreased eclosion rate of parasitoids were observed with increased arsenic treatment in soil. The results showed low concentration of arsenic in soil can transfer through food chain and can impact on higher trophic level species.
The functional response and spatial distribution of parasitoid may be useful for understanding host-parasitoid dynamics because information on these will give knowledge of the host-parasitoid interaction, which could lead to the development of strategy for biological control of insect pests. The functional responses of A. asychis on the green peach aphid and potato aphid was investigated in eggplant leaf-disc arena. As a result, among the three types of functional response, type III best described the A. asychis response to the aphid densities, according to the Bayesian Information Criterion (BIC). Functional response and spatial distribution of A. asychis on green peach aphid, Myzus persicae, was investigated on 5x5 eggplants in the net cage. After M. persicae were inoculated uniformly at the densities of 1, 3, 6, 9 and 12 (per plant) on upper, middle and lower leaves of each 25 eggplants, one mated female of A. asychis was introduced on the central eggplant. Each aphid density was duplicated. A. asychis showed a type II functional response different from that estimated on the eggplant leaf-disc arena. Although the initial distribution of the aphids in the 25 eggplants was uniform vertically and horizontally, the aphids became gradually concentrated on the upper leaves of eggplants, so did immature A. asychis.
As the results achieved by the evaluation of toxicities on an aphid parasitoid, Aphidius colemani by 79 pesticides registered as horticultural pesticide and 4 adjuvants for pest control, 6 insecticides including a-cypermethrin, 13 fungicides including metalaxyl-M+mancozeb and 4 acaricides including bifenazate showed low toxicity against A. colemani adult. Low toxicity was showed in all the 4 adjuvants as well. In residual toxicity test from 40 pesticides which showed toxicity more than 50%, A. colemani was safe from 11 pesticides from the 3th day after treatment, 7 pesticides from the 5th day after treatment and 14 pesticides from the 7th day after treatment, respectively. But, chlorpyrifos-methyl, diflubenzuron+chlorpyrifos, etofenprox+diazinone and imidachloprid+chlorpyrifos showed high toxicities reaching 100%, 97.7%, 100% and 100% respectively, even from the 7th day after treatment. To evaluate the control effect by A. colemani against Myzus persicae in a greenhouse, A. colemani was released at parasitoid versus aphids rates of 1:50 and 1:100 when the population of M. persicae was 50 per plant. After release, aphids population remained steady for 20 days after release at the level of around 60 aphids per plant During the investigation, insecticides for thrips control and fungicides for powdery mildew control were treated, but didn"t affect the mummy forming of A. colemani. It may be suggested from these results that the selected insecticides, fungicides, acaricides and adjuvent could be incorporated into the integrated M. persicae management system with A. colemani on greenhouse cultivation.