Japanese Pear Orchards Research Articles

Molecular verification of commercialized Neoseiulus californicus (McGregor) settlement before spider mite appearance in a Japanese pear orchard

A report of our earlier study described a phytoseiid mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) release system using a moisturized sheltered sachet for spider mite control. For the present study, we installed the predator release systems on 43 out of 71 trees in a Japanese pear orchard to survey the dispersal of N. californicus released from the predator release system. In the orchard, Japanese pear trees were trained on the overhead horizontal trellis system. Consequently, the trees were mutually connected through the trellis training system. We collected phytoseiid mites on the tree leaves and were subjected to PCR to examine their species composition. Results demonstrated that N. californicus were 62.37% of the total of 3,247 phytoseiid mites collected. Using microsatellite markers, commercialized N. californicus that had been released from the predator release systems were discriminated from indigenous N. californicus. Results demonstrated that phytoseiid mites consisting mainly of the commercialized N. californicus occurred one week earlier in trees with the predator release systems. Results also demonstrated that the commercialized N. californicus dispersal occurred mainly in trees installed with the predator release systems.

Optimization of the year‐round mowing schedule of a robotic lawnmower in a Japanese pear orchard

AbstractCommercial robotic lawnmowers have recently gained popularity in orchards. However, more widespread adoption of this technology in orchards requires optimization of the weed cutting height and cutting frequency. To determine the optimum weed cutting height, we tested a robotic lawnmower (Automower 430X, Husqvarna, Sweden) in a Japanese pear orchard at Ibaraki University, Ami, Japan. The mower was operated on short (weed height = 175 ± 42 mm (±SD), medium‐sized (weed height = 286 ± 87 mm) and tall weeds (weed height = 404 ± 118 mm). To determine the optimum cutting height and frequency, we used a weed growth model and data from photogrammetry, weed mechanical properties, and field performance. Our analysis indicates that the mower should be operated when the height of the weed reaches 20 cm. To maintain weed height at <20 cm, the mower, on average, should be operated 10 h week−1 between April 5 and October 13. We believe that the proposed mowing schedule would significantly help the mower tackle field challenges in the orchard.

Mutual complementarity among diverse pollinators as a mechanism underlying open insect pollination in Japanese pear orchards

AbstractCultivated Japanese pear varieties, mostly showing self‐incompatibility, require pollen transfer from other varieties. To elucidate the underlying mechanisms of open Japanese pear insect pollination, we first collected flower‐visiting insects using plastic vials and sticky traps in orchards located at different regions in Japan. Results showed that insects assigned to the families Andrenidae (Hymenoptera), Apidae (Hymenoptera), Halictidae (Hymenoptera), Syrphidae (Diptera) and Empididae (Diptera) are abundant in the orchards. Second, we restricted the flower‐visiting insects to access Japanese pear flowers using bags with mesh sizes of 0, 2 and 3.5 mm. Results indicated that insects which allowed to pass through bags with 3.5‐mm mesh size but not through bags with 2‐mm mesh size contribute primarily to pollination, represented as the fruit‐set ratio and seed number. Third, we measured head and thorax widths of the flower‐visiting insects and counted pollen grains on their body surfaces to estimate their pollination potential. Results indicated that insects assigned to the families Andrenidae, Halictidae, Syrphidae, Bibionidae (Diptera) and Muscidae (Diptera), including species with both widths smaller than 3.5 mm, harbour large quantities of Pyrus pollen grains, in addition to Apis mellifera (Apidae) with both widths greater than 3.5 mm. Consequently, the families Andrenidae, Apidae, Halictidae and Syrphidae might be the most important insect families for Japanese pear pollination. However, species identification of the flower‐visiting insects showed no common key species that contribute remarkably to pollination services other than A. mellifera. Consecutive insect collection using plastic vials and sticky traps demonstrated that compositions of the flower‐visiting insects are fluctuating continuously in the orchards. Nevertheless, year‐to‐year fluctuation of the fruit‐set ratio was less pronounced in open‐pollinated orchards than in hand‐pollinated orchards. These results suggest that mutual complementation among diverse pollinator species might be the mechanism underlying open Japanese pear insect pollination.

Biological control of the Japanese pear rust mite, Eriophyes chibaensis (Acari: Eriophyidae) and the Kanzawa spider mite, Tetranychus kanzawai (Acari: Tetranychidae) with Euseius sojaensis (Acari: Phytoseiidae).

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.

Control efficacy of the systemic acquired resistance (SAR) inducer acibenzolar-S-methyl against Venturia nashicola in Japanese pear orchards

Control efficacy of the systemic acquired resistance (SAR) inducer acibenzolar-S-methyl against Venturia nashicola in Japanese pear orchards

Weed Management and Economic Analysis of a Robotic Lawnmower: A Case Study in a Japanese Pear Orchard

The use of robots is increasing in agriculture, but there is a lack of suitable robotic technology for weed management in orchards. A robotic lawnmower (RLM) was installed, and its performance was studied between 2017 and 2019 in a pear orchard (1318 m2) at Ibaraki University, Ami. We found that the RLM could control the weeds in an orchard throughout a year at a minimum height (average weed height, WH: 44 ± 15 mm, ± standard deviation (SD) and dry weed biomass, DWB: 103 ± 25 g m−2). However, the RLM experiences vibration problems while running over small pears (33 ± 8 mm dia.) during fruit thinning periods, which can stop blade mobility. During pear harvesting, fallen fruits (80 ± 12 mm dia.) strike the blade and become stuck within the chassis of the RLM; consequently, the machine stops frequently. We estimated the working performance of a riding mower (RM), brush cutter (BC), and a walking mower (WM) in a pear orchard and compared the mowing cost (annual ownership, repair and maintenance, energy, oil, and labor) with the RLM. The study reveals that the RLM performs better than other conventional mowers in a small orchard (0.33 ha). For a medium (0.66 ha) and larger (1 ha) orchard, the RLM is not more cost-effective than RM and WM. However, the existing RLM performed weed control well and showed promise for profitability in our research field. We believe that, if field challenges like fallen fruit and tree striking problems can be properly addressed, the RLM could be successfully used in many small orchards.

Emergence of Glyphosate- and Glufosinate-resistant Italian Ryegrass (<i>Lolium multiflorum</i>) Populations in Japanese Pear Orchards in Japan and their Responses to Several Foliar-applied Herbicides

Emergence of Glyphosate- and Glufosinate-resistant Italian Ryegrass (<i>Lolium multiflorum</i>) Populations in Japanese Pear Orchards in Japan and their Responses to Several Foliar-applied Herbicides

First Report of Colletotrichum nymphaeae Causing Blossom Blight, Peduncle Rot, and Fruit Rot on Pyrus pyrifolia in Brazil

Colletotrichum species belonging to the C. acutatum, C. gloeosporioides, and C. boninense complexes were reported in Pyrus spp. to cause lesions on fruits and leaves (Fu et al. 2019). In November 2017, diseased flowers and peduncles were observed in a Japanese pear (Pyrus pyrifolia) orchard cultivar Hosui in Campo Largo and Quatro Barras, Parana, Brazil. On the surface of the decayed tissue, acervuli and orange conidial masses were found. Pure cultures were obtained following monosporic isolation and grown on potato dextrose agar (PDA) at 25°C with a 12-h photoperiod under fluorescent light for 7 days. The colony color was white to gray on the surface and orange on the bottom of the dish. The conidia were one-celled, hyaline, fusiform, and with a length and width ranging between 9 and 20 μm, and between 3 and 6.5 μm, respectively. These morphological characteristics correspond to Colletotrichum nymphaeae (Pass.) Aa and several other phylogenetically close species (Damm et al. 2012). In order to perform the pathogenicity test, a suspension containing 1 × 10⁴ conidia/ml was prepared from the monosporic isolates (PpCnPR17_02 and PpCnPR17_03) with 1-week-old cultures growing on PDA medium at 25°C with a 12-h photoperiod under fluorescent light. An aliquot of 20 µl of the suspension was deposited on the surface of flower structures, peduncles, and wounded ripe fruits of P. pyrifolia cultivar Hosui. Sterile distilled water drops served as controls. Each isolate treatment was arranged in a completely randomized design with five replications for fruit and peduncles and 10 replications for flowers. The inoculated structures were maintained in moist chambers for 20 days at 25 ± 2°C with a 12-h photoperiod under fluorescent light. Only the inoculated structures showed symptoms. Lesions, after inoculation, were observed in 3 days on flower structures, in 11 days on peduncles, and in 3 days on wounded ripe fruits. The pathogen was reisolated from the lesions. Colony and conidia morphology were identical to those of the original isolates, confirming Koch’s postulates. Fungal isolates were also characterized by sequencing of the internal transcribed spacer (ITS) rDNA using ITS1/IT4 primers, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) using GDF1/GDR1 primers, chitin synthase 1 (CHS-1) using CHS-354R/CHS-79F, and β-tubulin (TUB2) using BT2Fd/Bt-2b primers (Damm et al. 2012). Phylogenetic analysis was performed with the concatenated sequence alignment of four genes (ITS, GAPDH, CHS-1, and TUB2) using MEGA 6.0 software. The nucleotide sequences were deposited at GenBank (ITS, MK659663, MK659799; GAPDH, MK673275, MK673276; CHS-1, MK673273, MK673274; and TUB, MK681922, MK681923). A Bayesian inference phylogenetic tree showed that the isolates PpCnPR17_02 and PpCnPR17_03 from P. pyrifolia clustered in one separate clade with sequences of C. nymphaeae deposited at GenBank (CBS129928 and IMI370491). Isolates identified as C. nymphaeae are considered as part of the C. acutatum species complex (Damm et al. 2012). To our knowledge, this is the first report of C. nymphaeae causing symptoms in flowers, peduncles, and fruits of pear in South America.

Surface application of fertilizers and residue biochar on N<sub>2</sub>O emission from Japanese pear orchard soil

This study investigated soil N<sub>2</sub>O emissions following the application of fertilizers and pruning residue biochar on the soil surface of the Japanese pear orchard. Completely randomized design was laid out with four treatments: (1) control (unfertilized); (2) pig manure 300 kg N/ha and ammonium sulfate 200 kg N/ha with no biochar (F + BC0); (3) the same amount of manure and nitrogen (N) fertilizer with 2 t/ha biochar (F + BC2), and (4) with 10 t/ha biochar (F + BC10). The results showed that high N<sub>2</sub>O fluxes were observed after fertilization. Soil temperature and moisture were major controlling factors for N<sub>2</sub>O emission from the orchard soil. The lowest cumulative N<sub>2</sub>O emission (0.46 kg N/ha) was observed in the unfertilized control. Application of manure and N fertilizer significantly increased cumulative N<sub>2</sub>O emission compared to unfertilized control. Surface application of biochar (1.68 and 1.77 kg N/ha in F + BC2 and F + BC10, respectively) had no effect on soil N<sub>2</sub>O emission compared to F + BC0 (1.68 kg N/ha). Our results indicated that biochar pyrolyzed from orchard pruning residues can be returned to orchard soil as surface application without affecting soil N<sub>2</sub>O emissions.

PCR-based species identification applied in Japanese pear orchards to survey seasonal proportion changes of phytoseiid mite species

For this study, we developed a PCR-based method to identify the ribosomal internal transcribed spacer (ITS) sequences of six phytoseiid mite species found in Japanese pear orchards: Neoseiulus californicus (McGregor), Neoseiulus womersleyi (Schicha), Neoseiulus makuwa (Ehara), Amblyseius eharai Amitai and Swirski, Gynaeseius liturivorus (Ehara), and Amblyseius swirskii Athias-Henriot. Using the method, we can show seasonal proportion changes of phytoseiid mite species composition in Japanese pear orchards. Genomic DNA extracted individually from phytoseiid mites collected in the orchards are subjected to PCR of the ITS sequences using a universal primer set of which nucleotide sequences are conserved among the six phytoseiid mite species. Then, DNA samples showing PCR products with the universal primer set are used for another PCR of the ITS sequences using species-specific primer sets designed for respective phytoseiid mite species. Species-specific PCR is conducted in order of decreasing dominance of phytoseiid mite species. The method, which specifically identifies the six phytoseiid mite species irrespective of their sexes and developmental stages, might be useful for researchers who are lacking adequate morphological identification skills and nucleotide sequencing systems at their institutions.

Influence of pruning waste biochar and oyster shell on N2O and CO2 emissions from Japanese pear orchard soil

Two incubation experiments were conducted under controlled moisture and temperature conditions to determine the effects of soil amendment treatments based on pruning waste biochar and oyster shell, on N2O and CO2 emissions from an orchard soil. In experiment 1, four treatments were tested including, control (CK), pruning waste biochar at 2% (B2%), at 10% (B10%), and oyster shell (OS), mixed with soil from two different depths, namely, from the 0–5 cm and the 0–10 cm layers. In experiment 2, only the 0–10 cm soil layer was used to study the effect of surface application of pruning waste biochar (B2% and B10%) on soil N2O and CO2 emissions. The results showed that soil pH, total C and C: N ratio increased with biochar amendment treatments. Significant reduction in soil NO3− content was observed for the B10% treatment. Although OS application increased soil pH, no effect was observed on soil mineral N content, total C or C: N ratio. The rate of N2O emissions from the 0–5 cm soil layer after B2% and B10% addition, significantly declined by 12.5% and 26.3%, respectively. However, only the B10% treatment caused significant reduction in N2O emissions from the 0–10 cm soil layer and from surface soil, by 15.1% and 13.8%, respectively. Oyster shell application had no effect on either soil N2O or CO2 emissions from either soil layer tested. Our results suggest that the addition of pruning waste biochar at a high rate has the potential to mitigate N2O emissions from orchard soils; while, oyster shell can be used for liming without altering soil N2O nor CO2 emissions.

ナシ栽培ほ場における殺虫剤の複数年処理によるせん孔性害虫ヒメボクトウ（チョウ目：ボクトウガ科）被害の減少

ナシ栽培ほ場における殺虫剤の複数年処理によるせん孔性害虫ヒメボクトウ（チョウ目：ボクトウガ科）被害の減少

Seasonal Occurrence of Phytoseiid Mites in Urbanized Japanese Pear Orchards

Seasonal Occurrence of Phytoseiid Mites in Urbanized Japanese Pear Orchards

Identification of a Distinct Lineage of <I>Cacopsylla chinensis</I> (Hemiptera: Psyllidae) in Japan on the Basis of Two Mitochondrial DNA Sequences

Psyllids are a menacing pests of pears (Pyrus spp.) grown in temperate and subtropical regions of the world, including Taiwan and China. Pear psyllids belong to the large genus Cacopsylla (Psyllidae: Psyllinae). Among the 28 psyllid species that infest pear trees, Cacopsylla chinensis (Yang and Li, 1981) is considered the most harmful. Two psyllid outbreaks involving exotic species affected Japanese pear (Pyrus pyrifolia variety culta) orchards in the Saga Prefecture in July and November 2011. The psyllids were morphologically identical to the summer and winter forms of C. chinensis. In this study, we performed DNA sequence analysis of the mitochondrial cytochrome oxidase I-leucine tRNA-cytochrome oxidase II (COI-tRNA(Leu)-COII) and 16S rDNA regions to elucidate the phylogenetic relationships among 82 summer-form psyllids, five winter-form psyllids from several orchards in Japan, and those reported from Taiwan and China. The sequences of the COI-tRNA(LEU)-COII and 16S rDNA regions were identical among all 87 psyllids from Japan, regardless of summer/winter forms or orchards in Saga, Japan. Comparison of nucleotide sequences and phylogenetic analysis differentiated Japanese psyllids from the Taiwanese and Chinese C. chinensis isolates, with approximately 8 and 7% nucleotide difference in the COI-tRNA(LEU)-COII and 16S rDNA regions, respectively. The results suggest that C. chinensis possess a high level of genetic variability and that the psyllids responsible for the outbreak in Saga, Japan belong to a distinct lineage of C. chinensis.

Mating disruption of the carpenter moth, Cossus insularis (Staudinger) (Lepidoptera: Cossidae) with synthetic sex pheromone in Japanese pear orchards

Mating disruption of the carpenter moth, Cossus insularis Staudinger (Lepidoptera: Cossidae), with a synthetic version of its sex pheromone, a mixture of (E)-3-tetradecenyl acetate and (Z)-3-tetradecenyl acetate, was tested for three successive years in Japanese pear (Pyrus pyrifolia var. culta) orchards. Pheromone trap catches, percentage mating of tethered females, and tree damage were measured in both the pheromone-treated and untreated control orchards. The attraction of male adults to pheromone traps was completely disrupted, and the mating of the tethered females was completely inhibited by the treatment of synthetic pheromones. The percentage of damaged trees in the pheromone-treated orchard decreased over the course of the experiment, while the damage percentage did not decrease in the untreated orchard. These results show that mating disruption with the synthetic sex pheromone is promising for the reduction of damage caused by C. insularis in apple and Japanese pear orchards.

180 Effect of ground control difference on seasonal vegetation and aerobiology : A comparison of Japanese pear orchards and campus ground

180 Effect of ground control difference on seasonal vegetation and aerobiology : A comparison of Japanese pear orchards and campus ground

Seasonal Prevalence of Occurrence and Pesticide Susceptibility of Summer Fruit Tortrix Moth, Adoxophyes orana fasciata WALSINGHAM (Lepidoptera : Tortricidae) Occurred in Japanese Pear Orchards Using Pheromone-based Mating Disruptor

Seasonal Prevalence of Occurrence and Pesticide Susceptibility of Summer Fruit Tortrix Moth, <i>Adoxophyes orana fasciata</i> WALSINGHAM (Lepidoptera : Tortricidae) Occurred in Japanese Pear Orchards Using Pheromone-based Mating Disruptor

Relationship between sap flux density of Japanese pear and evapotranspiration in Japanese pear orchard

Relationship between sap flux density of Japanese pear and evapotranspiration in Japanese pear orchard

Acaricide-Mediated Suppression of Panonychus Citri (Mcgregor) (Acari: Tetranychidae) in Pear Orchards in Japan

Population density of the citrus red mite, Panonychus citri (McGregor), in Japanese pear orchards remained low until mid-August, even after inoculation of pear leaves with a considerable number of adult female P. citri from May onwards. This raised the possibility that pear leaves contain a natural compound that suppresses an increase of P. citri populations. The rate of development from larva to adult was significantly lower on leaves collected in July than on leaves collected earlier or later, in several years. The population suppression was caused by molting deterrent activity and ovicidal activity, according to our close observation in the laboratory. To clarify whether a natural pear compound caused this molting deterrence, a methanol crude extract of pear leaves was isolated and added to a newly developed artificial diet, consisting of sodium caseinate, sucrose, levulose, glucose and inositol. The compound extracted from pear leaves resulted in the molting deterrence as observed on pear leaves. Based on infrared and NMR spectral analysis, the compound extracted from pear leaves closely resembled the synthetic acaricide hexythiazox. Furthermore, the LC50 values of the compound extracted from pear leaves for ovicidal activity of P. citri eggs and for deterrence of molting to protonymphs were similar to those of hexythiazox. These results strongly suggest that the molting deterrent extracted from pear leaves was in fact hexythiazox, an acaricide in use on pear trees, rather than a natural product. This suggestion becomes even stronger, considering that the molting deterrence was observed in a hexythiazox-spray year, but not in a non-spray year.

福岡県におけるフェナリモル耐性ナシ黒星病菌の発生

Leaves and young fruits infected with Japanese pear scab were sampled from Japanese pear orchards in Fukuoka Prefecture in 2006 and 2007. Conidia collected from the samples were inoculated on the young leaves of potted pear trees previously sprayed with difenoconazole, fenbuconazole, hexaconazole, or fenarimol. Difenoconazole showed a high level of efficacy, while hexaconazole and fenbuconazole showed intermediate levels of efficacy. The efficacy of fenarimol was observed to be lower against the inocula from Fukuoka Prefecture as compared with that against the sensitive reference inocula. Fenarimol-resistant isolates are widely distributed in Fukuoka Prefecture.