• The Plant Pathology Journal
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• v.39 no.1
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• pp.52-61
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• 2023

Fire blight, caused by Erwinia amylovora, is one of the major bacterial disease of apple and pear, causing enormous economic losses worldwide. Several control measures against E. amylovora have been reported till date, however, none of them have proved to be effective significantly against the pathogen. In this study, mechanisms of the copper-based control agents (CBCAs): copper oxychloride (COCHL), copper oxide (COX), copper hydroxide (CHY), copper sulfate basic (CSB), and tribasic copper sulfate (TCS) and their disease severity reduction efficacy against E. amylovora were analyzed. Bis-1,3-dibutylbarbituric acid trimethine oxonol, carboxyl fluorescein diacetate succinimidyl ester, and 5-cyano-2,3-ditolyl tetrazolium chloride staining were used to check the damage of membrane potential, cytoplasmic pH_in, and respiration of CBCAs-treated E. amylovora, respectively. High disturbance in the membrane potential of E. amylovora was found under COX and COCHL treatments. Similarly, higher significant changes in the inner cytoplasmic pH_in were observed under COX, COCHL, and TCS treatment. CHY and COCHL-treated E. amylovora showed a significant reduction in respiration. In vitro bioassay results revealed that CHY, CSB, and TCS at 2,000 ppm reduced the severity of fire blight both in pre- and post-treatment of CBCAs in immature apple fruits and seedlings. Overall, the most effective CBCAs against E. amylovora could be CHY at 2,000 ppm as its showed inhibition mechanisms and disease severity reduction.

• The Plant Pathology Journal
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• v.39 no.4
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• pp.319-334
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• 2023

Plant disease is an important factor affecting crop yield. With various types and complex conditions, plant diseases cause serious economic losses, as well as modern agriculture constraints. Hence, rapid, accurate, and early identification of crop diseases is of great significance. Recent developments in deep learning, especially convolutional neural network (CNN), have shown impressive performance in plant disease classification. However, most of the existing datasets for plant disease classification are a single background environment rather than a real field environment. In addition, the classification can only obtain the category of a single disease and fail to obtain the location of multiple different diseases, which limits the practical application. Therefore, the object detection method based on CNN can overcome these shortcomings and has broad application prospects. In this study, an annotated apple leaf disease dataset in a real field environment was first constructed to compensate for the lack of existing datasets. Moreover, the Faster R-CNN and YOLOv3 architectures were trained to detect apple leaf diseases in our dataset. Finally, comparative experiments were conducted and a variety of evaluation indicators were analyzed. The experimental results demonstrate that deep learning algorithms represented by YOLOv3 and Faster R-CNN are feasible for plant disease detection and have their own strong points and weaknesses.

• Research in Plant Disease
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• v.25 no.2
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• pp.89-93
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• 2019

Fire blight disease caused by the bacterium, Erwinia amylovora, was observed in apple and pear orchards in Korea in 2015. Since then, it has spread, sometimes over long distances to other orchards. Therefore, we examined the ability of E. amylovora to survive in soils and on the surfaces of common materials such as T-shirts, wrist bands, pruning shears, and rubber boots by both conventional PCR (cPCR) and quantitative PCR (qPCR) methods. E. amylovora was detected in all materials tested in this study and survived for sufficiently long periods to cause fire blight disease in new sites. Thus, based on the results of this study, sanitation protocols must be applied to equipment during orchard work.

• Research in Plant Disease
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• v.19 no.4
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• pp.288-293
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• 2013

In worldwide, viral diseases of apple plants has caused the serious problems like reduced production and malformation of fruits. Also, the damages of apple plants by virus and/or viroid infection (Apple chlorotic leaf spot virus, Apple stem grooving virus, Apple mosaic virus, and Apple scar skin viroid) were reported in Korea. However there is few report about the protection approach against the infection by apple viruses. Therefore, this paper introduced the experimental protocol for the development of virus-free apple cultivars (Danhong, Hongan, Saenara, Summerdream). Apple plants were treated at $37^{\circ}C$ for 4 weeks and shoot tips were cultured in vitro. After heat treatment, the detection of apple viruses was performed by RT-PCR using virusspecific detection primers in new apple cultivars. With the heat treatments followed by in vitro shoot tip culture, the proportion of virus-free stocks of 'Danhong', 'Hongan', 'Saenara', and 'Summerdream' was 28%, 16%, 12%, and 12%, respectively. Taken together, this approach can be a good tool for production of virus-free apple stocks.

• Plant Disease and Agriculture
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• v.5 no.2
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• pp.100-104
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• 1999

A total of 65 isolates of Penicillium were isolated from decayed post-harvest fruits of apple pear citrus and grape. The Penicillium species isolated from the apple were idnetified as P. aurantiogriseum and P. expansum those from the pear were P. crustosum and P. expansum and those from the grape were P. aurantiogriseum and P. expansum, From decayed citrus fruits. P. digitatum and P. italicum were isolated. Citrinin and patulin from these species in the YES(yeast extract sucrose) broth were extracted with ethyl acetate and purified by thin-layer chromatography(TLC) and high performance liquid chromatography(HPLC) Among 51 isolates of Penicillium from apple pear and grape 7 isolates produced citrinin 13 isolates produces patulin and 12 isolates produced citrinin and patulin also. All 14 isolates of Penicillium from citrus produced only patulin.

• Electronics and Telecommunications Trends
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• v.38 no.3
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• pp.86-97
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• 2023

The outbreak of the novel coronavirus disease in 2020 caused a global semiconductor supply shortage and disruption in the production of devices such as iPhones owing to China's quarantine lockdown. Thus, Apple is diversifying its production bases from China to countries like India and Vietnam. The company is also accelerating semiconductor development to guarantee a stable supply, reduce design costs, and customize semiconductors with high quality and outstanding specifications for their products to outperform devices that use general-purpose semiconductors. Following the mobile application processor, Apple is releasing world-class semiconductors, such as the M1 and M2 chips that play the role of central processing units.

• Research in Plant Disease
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• v.12 no.3
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• pp.240-248
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• 2006

Control of white rot which is one of the most serious apple diseases in Korea has mainly relied on periodical spray of protective fungicides. As the main inoculum source of the disease is pycnidiospores produced in the warts formed on affected stems of apple tree, it can be conceivable that inhibition of spore production might be an effective means for controlling the disease. Inhibitory efficacy of eight selected fungicides against sporulation of the fungus was assessed by counting the number of spores produced at detached warts treated with the fungicides of recommended dilution. They showed diverse effect on sporulation. Carbendazim and azoxystrobin suppressed sporulation almost completely, the former irreversively. Thiram and folpet promoted sporulation as producing much more number of spores than untreated control. Others showed almost no effect on sporulation. Effects of suppression and promotion in the sporulation shown by the fungicides on the control of white rot were examined by incidences of disease and infection at the plots adopted the spray programs of which the fungicide at late May was substituted by carbendazim, azoxystrobin, folpet and thiram, respectively. Disease incidence and infection frequency at the plots sprayed former two chemicals which suppressed sporulation were much lower than those of the plots adopted latter two chemicals and untreated plot at which the fungicide spray was skipped at that time. These facts were reconfirmed in the experiments conducted with carbendazim and thiram, in which 100 fruits were bagged just prior to each spray from late May to late July for elucidating the effect of the two fungicides on the action of subsequent ones. Disease incidence and infection frequency on the fruit bagged just prior to each spray were gradually increased as the seasons going on. The increase rate at the carbendazim plot was much lower than that of thiram. Especially, the fruit infected till late July at the carbendazim plot were almost completely cured by the three fungicides, iminoctadine-triacetate, tebuconazole and samzinwang, a combined formular of iminoctadine-triacetate and difenoconazole, sprayed at late July and hence. In thiram plot, infected fruit were also cured by the 3 fungicides but not remarkable. From these results, it can be concluded that control efficiency of white rot can be greatly enhanced by selecting the fungicide capable of suppress the sporulation of white rot fungus at the season when the mass dispersal of spores is not initiated.

• Research in Plant Disease
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• v.24 no.4
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• pp.321-327
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• 2018

In 2018, symptoms of black rot on apple (Malus pumila var. dulcissima KOIDZ) cv. Fuji were observed in Yeongcheon-si, Korea. The fruit decay symptoms consisted of purple pimples spots, black rot around the seed cavity (calyx end), mummified fruit. To isolate the causal agent, small fragment (2 to 3 mm) of decayed tissue from the lesion margin were placed on WA or PDA. Fungal colonies on PDA produced dense white aerial mycelium, becoming dark gray with age. Pycnidia and conidia were observed under a light microscopy. The shapes of conidia were aseptate, ovoid, rounded at both ends, and $21.7-28.3{\times}9.9-15.3{\mu}m$. Based on morphological and cultural characteristics, this fungus was identified as Diplodia seriata. To confirm its identity, two loci (ITS and ${\beta}$-tubulin) were sequenced for molecular identification. BLAST searches indicated 100% identity with D. seriata. A pathogenicity test was conducted with isolates on Fuji apples. The apples were inoculated with mycelial plugs (5 mm) from 7-day-old cultures of the putative pathogens. All inoculated apples developed rot symptoms identical to the original symptoms, from which D. seriata were reisolated, fulfilling Koch's postulates. This study is the first report of black rot caused Diplodia seriata on apple.

• Korean Journal of Organic Agriculture
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• v.18 no.2
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• pp.221-232
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• 2010

During 2005~2009, current status on the occurrence and the management of the major disease, insect and mite pests were investigated in the non-chemical or organic cultured apple orchards in Korea. Numbers of certified organic or non-chemical apple orchards increased from 14 in 2005 to 78 in 2008. Severe damages on leaves and fruits were caused by the several diseases such as marssonina blotch, bitter rot, white rot, sooty blotch and flyspeck, and the several insect pests such as apple leaf-curling aphid, woolly apple aphid, oriental fruit moth and peach fruit moth on the almost certified organic or non-chemical pest control orchards. About 10 and 18 environmental-friendly materials were used to control diseases and insect or mite pests, respectively. But, lime sulfur and bordeaux mixture to diseases and machine oil, plant oil mixed with egg yolk, and pheromone mating disruptions to insect pests were effective under the adequate conditions.

• Research in Plant Disease
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• v.26 no.2
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• pp.95-102
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• 2020

The investigation of the infection rate of domestic apple orchards by four types of apple viruses (Apple chlorotic leaf spot virus [ACLSV], Apple stem pitting virus [ASPV], Apple stem grooving virus [ASGV], Apple mosaic virus [ApMV]) and one type of viroid (Apple scar skin viroid, ASSVd) found that most apple trees were infected with viruses and viroid at the rate of 97.3%. By region, the infection rate in Jeongseon stood at 98.8%, Danyang at 100%, Yesan at 100%, Jangsu at 89.1%, and Muju at 98.1%. By each virus and viroid, the infection rate of ASGV was the highest at 93.4%, followed by ASPV at 85.7%, ACLSV at 59.0%, ASSVd at 6.7%, and ApMV at the lowest 3.6%. In addition, 84.8% of the cases were infected with two or more types of viruses and viroid, nearly seven times the single type infection rate of 12.4%, and the cases infected with three viruses, ASPV, ACLSV, and ASGV accounted for 56.2%, more than the half the total number of trees investigated.