We measured the phototactic behavior of the western flower thrips, Frankliniella occidentalis (Pergande) under the LED light of various spectral content and intensity. The light intensity required to elicit a 50% behavioral response to the stimulus yielded the action spectrum of the phototactic behavior. The action spectrum peaks at 525 and 355 nm, between 355 to 660 nm. This profile reasonably fits the spectral sensitivity of the compound eye as determined by the electroretinographic method. In a choice experiment where the insects were subjected to select either 355 nm or 525 nm of equal photon flux, they preferred 355 nm to 525 nm, indicating that the insects prefer ultraviolet (UV) radiation under the condition of multiple light sources.
The western flower thrips, Frankliniella occidentalis Pergande and the onion thrips, Thrips tabaci Lindeman are major pests of Satsuma Mandarin (Citrus unshiu Marc.) fruits under greenhouse culture. To use thrips’ phototactic behavior for plant protection, we first determined the spectral sensitivity of the compound eyes of T. tabaci by recording electroretinogram. We then measured the action spectrum of phototaxis in flight activity in both species. Also measured the correlation between attractiveness of light and air temperature in both species. The compound eye spectral sensitivity exhibited two large sensitivity bands each peaking at 362 nm and at 532 nm. Both F. occidentalis and T. tabaci were strongly attracted to wavelengths around 350 nm. The attractiveness of 350 nm light was much stronger than that of 525 nm. The number of attracted individuals decreased as the air temperature dropped. We examined whether ultraviolet-emitting traps reduced the damage to fruits due to the thrips in greenhouses. As a result, ultraviolet-emitting traps were as effective as spraying of insecticides, Clothianidin and Acephate. Extensive browning on peels was found in the fruits irradiated with the light whose wavelength was shorter than 300 nm.
The purpose of this study was to determine the wavelengths of reflected light that attract and repel the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). The authors made 12 kinds of colored sticky board traps using Tyvek® sheets to reflect light and sharp-cut filters as optical filters and tested them in a greenhouse in which tomatoes were cultivated. By analyzing the number of whitefly catches on each sticky trap, we determined that the most attractive wavelengths were from 464 to 587 nm, and that wavelengths less than 464 nm repelled the insects.
In the laboratory, the adult rice leaf bug, Trigonotylus caelestialium (Kirkaldy), most preferred 375 nm light-emitting diodes (LED) among lights of four wavelengths ranging from 375 to 450 nm with constant light intensity. Under a rated output current condition, short-wavelength range LEDs (375 nm, 400 nm) attracted more bugs than long-wavelength range LEDs (505–600 nm). In the field, the prototype LED (375 or 400 nm) trap caught few adult bugs of the overwintering generation in the spring (April to mid-June), while it caught adult bugs continuously during the summer (late June to September). Many adult bugs of the presumed second generation, which is considered to be especially related to pecky rice damage, were caught in the trap from late July to mid-August. Thus, LED traps might be useful tools to monitor T. carestialium under field conditions.
In order to develop an economical pest-control lighting system for two noctuid species, Helicoverpa armigera and Mamestra brassicae, we investigated the daily activity of these two species with illumination at night. The compound eye spectral sensitivity of the two moths showed peaks at 360 nm and 500—550 nm. We selected green LED peaking at 535 nm for the lighting device, because this wavelength has little effect for plants. The light intensity was 2.5×1017 photons·m-2·s-1 at a distance of 10 cm from the light source. We recorded the activities of moths using an actograph, and compared the activities at night with and without the green illumination. Continuous illumination at night reduced the activities most effectively in both species. While a 0.2 Hz flickering condition (0.5 sec ON and 4.5 sec OFF) significantly suppressed the activity in H. armigera, no significant effect of flickering light was detected in M. brassicae.
The West Indian sweet potato weevil, Euscepes postfasciatus Fairmaire, was distributed only on Nansei and Ogasawara (Bonin) Islands in Japan until 2008, when the weevil was found for the first time in Ibusuki City, which previously regarded as a weevil-free area. In this study, we used epidemiological approaches to determine how the weevil population in Ibusuki City was established. We conducted spatial distribution analysis and case–control studies based on survey data gathered from 270 farmers who cultivated sweet potato in 2008. Weevils were present at 46 sweet potato (Ipomoea batatas) cultivation sites and four blue morning glory (Ipomoea indica) growing sites. The weevil infestation rate was higher in sweet potato plants than in wild host plants. Weevil infestation was strongly associated with the use of tuber trench silo storage (odds ratio, 4.45). The association with silo storage suggested that the tuber storage silos provided an overwintering refuge for the weevil. The case–control study also revealed that cultivation without pesticides and for home use were associated with weevil infestation. Activities such as the transfer of tubers or leaving tubers in the field may expand the distribution of the weevil population over a wider area.
We investigated effects of sugar solution on adult longevity, progeny production and progeny sex ratio of Aphidius ervi in the presence and absence of host aphids. When female parasitoids were provided with 50% glucose–fructose solution in 1 : 1 ratio, they lived approximately twice longer than those provided with distilled water, irrespective of host aphid provision. The same effect of sugar solution was also observed on progeny production. When the parasitoid was fed sugar solution, its lifetime progeny production approximately doubled in comparison to that provided with water, whereas daily progeny production did not differ. Total number of female progeny did not differ between adult female provided with water and sugar solution, but significantly larger number of lifetime male progeny production was observed in females provided with sugar solution than females fed with water, because only male progeny was produced by females fed with sugar solution late in oviposition period.
To detect biological differences between pyrethroid-resistant strains and pyrethroid-susceptible strains of the onion thrips, Thrips tabaci, developmental and ovipositional characteristics on the leaves of 5 varieties of persimmon and green bean were investigated by rearing trials using isofemale lines. In addition, suitability of 2 varieties of persimmon fruits as foods for thrips larvae was compared between a pyrethroid-resistant strain and a pyrethroid-susceptible strain of onion thrips. Irrespective of susceptibility levels to pyrethroid, while T. tabaci adults deposited eggs into persimmon leaves, few individuals completed larval development on the leaves, suggesting that T. tabaci does not develop on persimmon leaf throughout reproductive seasons. Both strains of T. tabaci successfully molted into adults when they fed on persimmon fruits, but survival rates in immature stages differed among varieties and developmental stages of the fruits. These differences may cause inter-specific and seasonal variation in injury levels by thrips attacking persimmon orchards. The pyrethroid-resistant strains showed lower fecundities compared to the pyrethroid-susceptible strains of onion thrips on green bean leaf. In conclusion, there was no evidence that unique characteristics other than susceptibility levels to pyrethroid insecticide contribute to pestilent levels of the onion thrips in commercial persimmon orchards.
Scirpus juncoides is a noxious weed species in rice fields that intensifies damage to rice grains caused by the sorghum plant bug Stenotus rubrovittatus, by serving as the oviposition site. In this study, we examined whether herbicide application for the elimination of S. juncoides has a controlling effect on the bug. In the non-bentazon-applied fields, the bug's invasion into the rice fields prior to the heading period of rice and the nymphal emergence were observed. When bentazon was applied 41 days or 62 days after transplanting in S. juncoides-infested rice fields, the bug's invasion into the fields occurred only after the heading period of rice, and the nymphal emergence of the bugs was not observed. When bentazon was applied 77 days after transplanting, the bug's occurrence resembled that in the non-bentazon-applied fields. These results indicated that the bug's propagation could not be avoided, when the herbicide application timing is later than the occurrence of the first-generation adults. The effects of the timing on damage to rice grains were unclear. Therefore, judging from differences in the bug's occurrence between the rice fields studied, it seems reasonable to conclude that the elimination of S. juncoides with herbicides before the occurrence of the first-generation adults is effective for the control of the bug.
We assessed the impact of sika deer (Cervus nippon yesoensis) density on the abundance, diversity and species composition of forest dung beetle communities. We used baited-traps to collect dung beetles in habitats with two different sika deer densities near Lake Toya, Hokkaido, Japan; Nakajima Island (high-density) and the nearby lakeshore forest (low-density). Overall, our results showed that dung beetle abundance was associated with higher deer density. Although differences in dung beetle species richness, diversity index and beta diversity were not statistically significant among deer densities. NMDS analysis showed that dung beetle community composition did vary with deer density. Our results indicate that, where deer density is high, the dung beetle community characterized by grassland species, including Caccobius jessoensis, Aphodius pusillus and A. rectus. Conversely, where deer density is low, the dung beetle community comprises forest species such as Phelotrupes laevistriatus. Our study suggests that deer density strongly influences dung beetle species abundance via the volume of deer dung. Additionally, we show that forest dwelling dung beetle species give way to grassland dwelling species at higher deer densities.
Recently, Thrips nigropilosus is recognized as a predominant pest on chrysanthemum in Okinawa Prefecture, southwestern Japan. Since this species has long been regarded as a minor pest of asteraceous crops, there is little information on the pesticide susceptibility of the species. In this study, we examined the insecticidal effects of 18 commercially available agrochemicals on adult females and larvae of T. nigropilosus under laboratory conditions. As a result, nine insecticides including an organophosphate, a carbamate, a synthetic pyrethroid, neonicotinoids, and others were highly effective for both adults and larvae irrespective of their origin. The mortality rates in acephate, acrinathrin, bifenthrin, and thiamethoxiam varied between the two populations tested, suggesting variation in susceptibility to these chemicals. Malathion was the only compound which was ineffective against T. nigropilosus.