We investigated the number of airborne pollen of Japanese cypress, Chamaecyparis obtusa Endl., the density of stink bugs, Plautia crossota stali Scott, on the cones of Japanese cypress, and the damage to persimmon fruit by stink bugs in Wakayama Prefecture. In years when the density of overwintering adult bugs was high and the airborne pollen count was low, the peak density of the bug population on Japanese cypress cones was observed as early as July–August and the percentage of damaged persimmon fruit was high. In contrast, the bug population reached peak density in September–October and a low percentage of damaged fruit was observed in years when the density of overwintering adult was low and the airborne pollen count was high. The decrease in bug density on cones, which indicates cone deterioration, was followed by bugs leaving the cypress for persimmon orchards. There was a highly positive relationship between the density of overwintering adults and the number of airborne Japanese cypress pollen, which is closely related to cone production. Thus, the ratio of airborne pollen counts in the current year to that in the previous year (the c/p pollen ratio) is considered an indicator of the stink bug population for the current year. A highly positive relationship was found between the c/p pollen ratio and the time when the percentage of damaged fruit increased, suggesting that the c/p pollen ratio is very useful for forecasting the damage rate of persimmon fruit.
We developed a technique of simultaneously releasing adults and eggs of Orius strigicollis to enhance its early establishment in greenhouses. We first sought suitable oviposition substrates and alternative diets for O. strigicollis adults. Among three species of plants examined as oviposition substrates, the hatchability of eggs was best on Sedum rubrotinctum shoots. Fresh honey was as effective as the eggs of Ephestia kuehniella Zeller, a conventional diet, in increasing the longevity of O. strigicollis adults, indicating that fresh honey can be used as an alternative diet for O. strigicollis. At least one shoot of S. rubrotinctum must be provided per two O. strigicollis females to obtain eggs effectively. About 1,100 eggs were obtained from one bottle of O. strigicollis (Tairiku®, 250 adults) when they were reared with S. rubrotinctum shoots and fresh honey for three days. The number of O. strigicollis offspring found on sweet peppers was increased when eggs of O. strigicollis were released with adults at the same time, suggesting that the simultaneous release of eggs and adults of O. strigicollis was effective in enhancing its early establishment.
We developed a method for preventing the escape of commercial European bumblebees (Bombus terrestris) from greenhouses using plastic nets. We selected a mesh size (4.0×4.0 mm) based on the body size measurements of individual bees in five mature commercially obtained colonies. From 2004 to 2005, we covered the sides, ceiling, and entrances of more than 2,500 greenhouses with nets in Biradori-cho, Hokkaido, Japan. Compared to surveys conducted in 2002 and 2003, the number of bees collected outside the greenhouses markedly declined in 2004 and 2005, corresponding to the increasing percentage of covered greenhouses near the survey sites. Thus, covering the sides, ceiling, and entrances of greenhouses with 4.0×4.0 mm plastic mesh is an effective means of preventing the escape of B. terrestris, and reducing the density of this bee in the surrounding fields.
We investigated the mating, oviposition, and prey use by larvae of Hypsopygia postflava, a moth that is parasitic on nests of the paper wasp, Polistes jokahamae, in the laboratory under natural temperature, humidity, and day-length conditions, and in field cages. Mating occurred mainly from 2300 to 0600 hours, and copulation lasted a mean of 80.4 min. When adult wasps were absent from the nest, female adults of the moth laid eggs singly or in clumps of a few eggs, mainly on the walls of cells containing cocoons with live pupae or pupal exuviae. When adult wasps were present on the nest, wasp attacks prevented female moths from approaching the nest, and so they laid eggs singly or in clumps of several tens around the base of the nest pedicel. Female moths laid a mean of 133.9 eggs during their mean lifetime of 10.7 days. When first-instar larvae were released 10 cm from the base of the nest pedicel, 55% of them arrived in the nest with adult wasps. Moth larvae fed on wasp pupae first, and then on wasp larvae.
The daily periodicity of sex pheromone emission by females of the rice leaf bug, Trigonotylus caelestialium, was examined. Male bugs were captured at any time of the day in traps baited with 10 virgin females placed in a field overgrown with weeds. In the laboratory, thirty pairs of virgin adults three days after emergence were released in the rearing cage at different times of day, and the number of mated females was checked 4 h later. The percentage of mated females was more than 60% regardless of the time of release and the light conditions. These results suggest that there is no daily periodicity in sex pheromone emission by females and mating.
The sorghum plant bug, Stenotus rubrovittatus, lays eggs and feeds on the spikelets of gramineous plants. To develop a simple method for rearing this insect under laboratory conditions, we applied millet Setaria italica seedlings both as a substrate for egg deposition and as food for nymphs and adults. Adult females laid eggs between the sheath leaf and the first leaf sheath, or on part of the fold blade of the first leaf. The growth period from egg hatching to adulthood was 12.1 days in females and 11.3 days in males under 25°C and LD16 : 8 conditions. The adult emergence rate from first instar nymphs was 60%. The preoviposition period was 4.3 days. These results were similar to a previous report using wheat or Italian ryegrass ears as food and the oviposition substrate.
Bemisia tabaci adults were exposed to a tape formulation of pyriproxyfen for 5 min in a plastic cylinder (7 cm diam.×18 cm). The treated adults were allowed to lay eggs for 24 h on a bean leaf which bore eggs laid by untreated adults. In reciprocal experiments, untreated adults were allowed to lay eggs on a bean leaf which bore eggs laid by treated adults. Other experiments were conducted to assess the mortality of control eggs which were totally unaffected by treated adults. The mortality of eggs laid by untreated adults exposed to treated adults was significantly higher than that of control eggs. These findings showed that pyriproxyfen was transported by B. tabaci adults which had been exposed to the tape formulation.