To optimize operating conditions and the selection of pesticides suitable for spraying from UAVs, we evaluated the coverage of sprayed droplets in the range of 0.001–100

Species of generalist phytoseiid mites in the genus Euseius are effective natural enemies of multiple arthropod pests in various types of orchards worldwide. Cover crops increase the densities of these predators and can help reduce pest densities, but their practical roles and effects in enhancing biological control have not yet been completely unveiled yet. Here, we examined the efficacy of biocontrol of Panonychus citri (McGregor) and Aculops pelekassi (Keifer) by naturally occurring Euseius sojaensis (Ehara) in commercial Japanese citrus orchards with cover crops of Lolium perenne L. (perennial ryegrass) managed in two different ways: flowering and mowing. In the flowering plots, the numbers of windborne pollen grains and phytoseiid mites were larger, P. citri populations were smaller, and rates of fruit injury caused by A. pelekassi were significantly lower than in mown plots. In early summer, the number of E. sojaensis in the flowering plots peaked following a peak in the abundance of windborne Poaceae pollen caught on the citrus trees. These results suggest that the windborne pollen supplied from cover crops of L. perenne boosts the populations of E. sojaensis inhabiting the citrus trees and enhances the efficacy of biocontrol of P. citri and A. pelekassi. The percentage of E. sojaensis females with eggs was higher in flowering plots than in mown plots. Therefore, in conservation biological control, a perennial ryegrass cover crop flowering in early summer would be beneficial for increasing the fecundity of this predatory mite, even when prey (pest) densities are low.

Euseius sojaensis (Ehara) is an effective indigenous predator of multiple arthropod pests in orchards in Japan. Population increases of this generalist phytoseiid mite correspond to those of the most important vineyard pest, Scirtothrips dorsalis Hood. However, the efficacy of biocontrol by it had not been evaluated. Here, we examined the biocontrol of S. dorsalis and Tetranychus kanzawai Kishida by E. sojaensis on two table grape cultivars, less hairy cultivar ‘Pione’ and hairy cultivar ‘Shine Muscat’. In greenhouse experiments, phytoseiid populations were larger, pest populations were smaller, and the incidence of fruit injury caused by S. dorsalis was significantly lower in E. sojaensis -release plots than in no-release plots. Densities of S. dorsalis larvae and T. kanzawai and the incidence of fruit injury were higher in hairy cultivar than in less hairy cultivar. These results suggest that E. sojaensis can control S. dorsalis and T. kanzawai populations simultaneously, but to different degrees between the cultivars. In laboratory experiments, E. sojaensis consumed fewer pests on leaf discs of hairy cultivar than on those of less hairy cultivar. The greater trichome density may hinder these large phytoseiid mites and thus reduce biocontrol efficacy. The interactions among phytoseiid mites and pests via plant leaf structure need to be clarified for successful biological control.

Intraguild predation (IGP) and cannibalism influence the effectiveness of biological control with generalist predators. In Japanese citrus orchards, two generalist phytoseiid species, Euseius sojaensis (Ehara) and Amblyseius eharai Amitai et Swirski, occur simultaneously, but only the former can control Aculops pelekassi (Keifer). First, we investigated the intensity of IGP and cannibalism in E. sojaensis and A. eharai in the presence and absence of pine pollen, which is a high-quality alternative food for these predatory mites. Amblyseius eharai was a stronger intraguild predator and cannibalistic predator than E. sojaensis with or without pollen. In the presence of pollen, although IGP and cannibalism were relaxed in both species, they were not dramatically reduced in A. eharai. Next, we investigated the effects of IGP and cannibalism on A. pelekassi control by changing the release ratio of E. sojaensis and A. eharai in the presence of pollen. With release of E. sojaensis alone, the E. sojaensis population increased and thus A. pelekassi was controlled. With release of A. eharai alone, however, the A. eharai population did not increase and thus A. pelekassi was not controlled. Simultaneous release of E. sojaensis and A. eharai reduced the rate of E. sojaensis population increase. Moreover, A. pelekassi densities were higher with a higher release ratio of A. eharai. These results suggest that A. eharai diminishes the biological control efficiency of the phytoseiid complex owing to IGP and cannibalism, even in the presence of high-quality food, and thus could indirectly increase pest populations.

Euseius sojaensis (Ehara) is an effective indigenous natural enemy of some eriophyid mites and spider mites in Japan. However, pesticides that are toxic to it are frequently applied in commercial Japanese pear orchards until early summer, when the predator densities are at their peak. Here, we examined the suppressive effect of inoculative release of E. sojaensis on Eriophyes chibaensis Kadono and Tetranychus kanzawai Kishida under conservation control using selective pesticides from late April to late June. The densities of E. sojaensis peaked in early June. In E. sojaensis-release plots, phytoseiid populations were larger, E. chibaensis and T. kanzawai populations were smaller, and rates of leaf mosaic and russeting caused by E. chibaensis were significantly lower than in control plots. These results suggest that E. sojaensis can control E. chibaensis and T. kanzawai populations simultaneously. As it may be difficult to suppress E. chibaensis densities below the control threshold of 50 mites per leaf only by conservation using selective pesticides, enhancement and augmentation of E. sojaensis for sustainable control of mites should be considered as an option in commercial Japanese pear orchards.

マルチローター式無人航空機(XAG社製P-20)により散布された液滴の付着性に及ぼす飛行経路と散布粒径の影響を,感水試験紙を用いてカンキツ樹冠内の高さや感水試験紙面の方向別に評価した。その結果,マルチローターは,散布時に植栽列上を直線的な飛行経路をとるよりも樹上を螺旋状に飛行するほうが被覆面積率は高くなり,散布粒径 100~195 μmの範囲では小さいほど被覆面積率が高くなった。また,被覆面積率は樹冠内の付着面の向きや高さによって異なり,これらの要因ごとに飛行経路や散布粒径が被覆面積率に及ぼす効果も異なった。これはマルチローターからのダウンウォッシュやそれが地面から跳ね返った気流が薬液の付着性に寄与するためと考えられた。

Five phytoseiid mite species: Phytoseiulus persimilis Athias-Henriot, Neoseiulus californicus (McGregor), Neoseiulus womersleyi (Schicha), Amblyseius eharai Amitai and Swirski, and Euseius sojaensis (Ehara) (Acari: Phytoseiidae) were collected from commercial Japanese pear orchards in Shizuoka Prefecture. To evaluate the suppressive effect of generalist phytoseiid species on the spider mite Tetranychus kanzawai Kishida (Acari: Tetranychidae), we compared four treatments (E. sojaensis release, A. eharai release, synthetic pyrethroid application, and no -release) performed in a greenhouse. These treatments were conducted when T kanzawai densities were low, and pine pollen was provided as alternative food for predatory mites in all treatments. At late June, the peak densities of T kanzawai were significantly low in E. sojaensis release and in no-release compared with in pyrethroid application and in A. eharai release. The dominant phytoseiid species in E. sojaensis release and in no release was E. sojaensis. After July, however, E. sojaensis densities became lower in E. sojaensis release as well as no-release, and thus T kanzawai densities became higher in all treatments at early August. These results suggest that conservation and augmentative release of E. sojaensis prior to T kanzawai population increase, might suppress the outbreak of this spider mite in Japanese pear orchards until early summer.

Dithiocarbamate fungicides, such as mancozeb and maneb, are sprayed on Satsuma mandarin trees 3 or 4 times during the summer to control major diseases, but laboratory experiments using these chemicals have shown negative effects on phytoseiid mites. Here we evaluated the effects of mancozeb and four alternative fungicides - kresoximmethyl, dithianone, oxine-copper, and copper hydroxide with calcium carbonate - on the occurrences of phytoseiid mites and their prey Panonychus cirri (McGregor) (Acari: Tetranychidae) in neonicotinoidtreated Satsuma mandarin fields. As expected from laboratory findings, mancozeb application reduced the overall population of phytoseiid mites, which was mainly composed of Amblyseius eharai Amitai and Swirski (Acari: Phytoseiidae), and increased the P cirri density. In contrast, the four alternative fungicides did not adversely affect the phytoseiid mite population, and three of these treatments - kresoxim-methyl, dithianone, and oxine-copper - did not increase the P cirri density. From these results, we encourage careful selection of fungicides when the native natural enemy A. eharai is used for the control of P cirri.

Euseius sojaensis (Ehara) (Acari: Phytoseiidae) is an effective indigenous natural enemy of Aculops pelekassi (Keifer) (Acari: Eriophyidae). However, dithiocarbamates, which are seriously harmful to E. sojaensis, are usually applied in commercial citrus orchards in June when the density of this phytoseiid mite peaks. In this study, we examined the suppressive effect of the E. sojaensis release on A. pelekassi in conservation control by using selective pesticides until late June. In the E. sojaensis release plot, phytoseiid populations were larger, A. pelekassi populations were smaller, and the rate of fruit injury was lower than those in the no-release plot; these differences were significant in some years. Many phytoseiid mites were observed in conservation-control orchards, with E. sojaensis being the dominant species; however, only a few phytoseiids occurred in conventional-control orchards. These results suggest that E. sojaensis was conserved by using selective pesticides and the initial density of A. pelekassi was reduced by this phytoseiid mite. However, it is difficult to control fruit injury only by conserving E. sojaensis, because it generally disappears after July. Therefore, we should study the possibilities for enhancement of E. sojaensis populations from summer onwards for sustainable biological control of A. pelekassi.

The pink citrus rust mite, Aculops pelekassi (Keifer) (Acari: Eriophyidae), is a serious pest and is widely distributed in most citrus-growing areas of the world. Euseius sojaensis (Ehara) and Amblyseius eharai Amitai and Swirski (Acari: Phytoseiidae) are indigenous generalist predatory mites in Japanese citrus orchards. Although these two species prey upon some eriophyid mites, A. pelekassi is not considered to be a suitable food for their development and reproduction. In this study, we examined the suppressive effect of these two predators on A. pelekassi density when provided with pine pollen as an alternative food. In a growth chamber experiment, pollen provisioning led to population increase of E. sojaensis and A. eharai, but only E. sojaensis significantly decreased A. pelekassi populations. In a field experiment, E. sojaensis release suppressed A. pelekassi populations on both leaves and fruit. Fruit injury by A. pelekassi in October was suppressed by E. sojaensis release or pollen provision. These results suggest that E. sojaensis can serve as an effective biological control agent against A. pelekassi when provided with pine pollen. Therefore, maintaining populations of E. sojaensis by means such as pollen provisioning could lead to successful biological control of the eriophyid mite in Japanese citrus orchards.

Two generalist phytoseiid mites, Amblyseius eharai Amitai and Swirski and Euseius sojaensis(Ehara)(Acari: Phytoseiidae), are useful biocontrol agents in citrus fields, and their reproduction is expected to be enhanced by supplying alternative foods. We reared phytoseiid mites on the pollen of six tree species and evaluated the effect on reproduction. The intrinsic rate of natural increase(rm)of A. eharai was 0.179 to 0.216 when the pollen of Pinus thunbergii, Distylium racemosum, Camellia sinensis, or Morella rubra was provided, suggesting that these four types of pollen were suitable for the reproduction of A. eharai. When pollen from Citrus natsudaidai and Cryptomeria japonica was provided, rm was lower(0.085, 0.082)but still positive, because the net reproduction rates(R0)were lower and the mean generation times(T)were longer than with the above four pollen types. E. sojaensis had rm of 0.166 to 0.196 when P. thunbergii, D. racemosum, C. sinensis, or M. rubra was provided, which appear to support E. sojaensis reproduction. However, with C. natsudaidai and C. japonica pollen, the R0 was extremely low and the rm was negative. Based on these results, the pollen of P. thunbergii, D. racemosum, C. sinensis, and M. rubra are suitable foods for the reproduction of these two species of generalist phytoseiid mites.

For 2 years we investigated the occurrence of Panonychus citri and its natural enemies in 30 citrus fields in eastern, central, and western Shizuoka Prefecture. Panonychus citri female abundance increased in fields with low frequencies of petroleum oil application or high frequencies of insecticide application. The main natural enemy species were Stethorus spp., Oligota spp., and Neoseiulus californicus. Stethorus spp. dominated in the east and increased in abundance in fields with higher densities of P. citri, but it was rarely observed in central or western Shizuoka Prefecture; notably, the application frequency of insecticides harmful to Stethorus spp. was lower in the east than in the other two areas. Neoseiulus californicus and Oligota spp. were observed in all three areas, and N. californicus abundance increased in fields with higher densities of P citri. The density of N. californicus per P citri was highest in the west, where Stethorus spp. were rarely found, and lowest in the east. Our findings suggest that the species composition of natural enemies was affected by insecticide application. Panonychus citri density was lower in the east than in the other two areas, suggesting that Stethorus spp. was a more effective predator than N. californicus at low prey densities.

We summarize the status of the biological control of insect pests in citrus IPM in Japan. Classical biological control against exotic insect pests was used from the 1910s to 1980s. And some species of introduced natural enemies have been maintaining pests at below the economic threshold in the present citrus cultivation. However, the late 1990s, conservation biological control of the citrus red mite Panonychus citri (McGregor), with severe pesticide resistance was investigated. As a result, acaricide applications were reduced by two or three times by the late 2000s through insecticide selectivity and cover cropping to maintain the habitat for natural enemies. We also discuss the issues of biological control for the establishment of citrus IPM.

We investigated the ability of phytoseiid mites in intercropped barley to suppress onion thrips (Thrips tabaci Lindeman) on Welsh onion in the laboratory. Ten adult females of T. tabaci were released into a cage containing Welsh onion seedlings planted in a pot and intercropped with barley transplanted from a Welsh onion field. For comparison, insecticide-treated barley and soil from the Welsh onion field were tested. At 20 days after release, the number of T. tabaci was lowest (significantly) in the untreated barley, but there was no change in the treated barley. Phytoseiid mites (mainly Gynaeseius liturivorus (Ehara)) were observed only in untreated barley.

The first generation of crawlers of arrowhead scale Unaspis yanonensis (Kuwana) occur in citrus orchards from early May to late July. Insecticide application is generally carried out to control U. yanonensis during the peak days of larval occurrence in June. We demonstrated that a high synergistic effect in controlling U. yanonensis was observed with the combined application of petroleum oil (9.7 g/L) and buprofezin (0.2 g/L) at the adult stage in late April. However, independent application of each insecticide during this time was less effective in controlling U. yanonensis.

I investigated the impact of insecticide application on the population density of Panonychus citri(McGregor)in two citrus orchards in Shizuoka Prefecture with different species of mite predators. In one citrus orchard, Neoseiulus californicus(McGregor)was the main mite predator species. The application of tolfenpyrad reduced the density of N. californicus and resulted in an increase of P. citri, whereas the application of imidacloprid or chlorfenapyr did not affect the densities of N. californicus and P. citri. In the other citrus orchard, Stethorus spp. were the main mite predator. The application of imidacloprid reduced the density of the predators and increased the density of P. citri, whereas the application of chlorfenapyr did not affect the density of P. citri and the predators. The application of tolfenpyrad reduced the density of the predators, but P. citri did not increase. These results demonstrate that biological control of P. citri requires careful selection of insecticides that will not have a detrimental effect on the region-specific species of mite predators in citrus orchards.

静岡県内のジチオカーバメート系薬剤の散布状況が異なる３圃場で採集したミカンサビダニに対する各種薬剤の殺虫効果を評価した。その結果，すべての個体群に対してマンゼブおよびビフェナゼートの効果が低いと判定された。一方，すべての個体群に対して，レピメクチン，ミルベメクチン，ルフェヌロン，アミトラズ，アセキノシル，ピリダベン，トルフェンピラド，スピロメシフェン，フルアジナム，キノキサリンの効果が高いと判定された。さらに，１個体群で本害虫に登録がない薬剤の殺虫効果を検定した結果，エチプロール，スピノサド，ピリフルキナゾン，ヘキシチアゾクス，ブプロフェジン，スピロテトラマト，シエノピラフェン，シフルメトフェン，シアントラニリプロール，フルベンジアミド，メパニピリムの効果が高いと判定された。これらミカンサビダニに対する殺虫効果が高い薬剤の中には，カンキツ微小害虫の土着天敵に対する影響が大きい薬剤も含まれるため，ミカンサビダニの化学的防除では土着天敵に悪影響を及ぼさないよう，使用薬剤の種類や散布時期に注意する必要がある。

We tested two cultivars of barley and one of wheat as living mulch for the retention of indigenous natural enemies of pests of winter-harvested Welsh onion. ‘Hyakumangoku’ barley withered earliest and was therefore most suitable to precede soil hilling for the blanching of the onions in early September; it supported populations of Rhopalosiphum padi (Linnaeus) and Anaphothrips obscurus (Müller), which are food sources for the indigenous natural enemy Geocoris proteus Distant, and various predatory phytoseiid mites.

Alternative food sources provided by wheat and barley living-mulch were evaluated for the effect on the life history traits of the predatory bug, Geocoris proteus Distant. As alternative food sources, Rhopalosiphum padi (Linnaeus) and Anaphothrips obscurus (Muller) were provided to larvae and adults of G. proteus. Onion thrips, Thrips tabaci Lindeman and a standard food, Ephestia kuehniella (Zeller) eggs served as control food sources. The results showed that R. padi significantly prolonged the larval period and preoviposition period of G. proteus compared to the other prey species. However, R. padi made the female bugs more fecund than T. tabaci, though not so much as the standard food. Anaphothrips obscurus, though less than the standard food, was also nearly equal to T tabaci in fecundity of the bugs. As a result, R. padi and A. obscurus were superior or nearly equal to T tabaci in affecting the intrinsic rate of natural increase of G. proteus. These results suggest that wheat and barley would provide preferable alternative foods to G. proteus, thus serving well as living mulch.

Irradiation of melon (Cueumis melo) seedlings with red LED light (wavelengths of 620 to 630 nm) at an intensity of 1X10(18) photons m(-2) s(-1) decreased the number of Thrips palmi (melon thrips), a major insect pest that causes serious damage during greenhouse melon cultivation. Thrip populations were significantly lower than in treatments without LED, both with continuous 24-h irradiation and with 12-h daytime (06:00 to 18:00) irradiation. Transplanted seedlings were also irradiated with red LED light of two different intensities (4.7X10(18) photons m(-2) s(-1) or 1.0X10(18) photons m(-2) s(-1)) in two cultivation environments (glass or plastic greenhouse). These findings suggest that irradiation with red LEDs may be an effective means of controlling Thrips palmi in greenhouse melon cultivation.