Plant Disease

Sweet corn, silage and grain crops have been facing the threat of severe corn disease for many years, spreading to various parts of Israel. Over the past few years, we conducted a series of field experiments, with the assistance of Netafim Israel, growers' associations and farmers from the Galilee region. In 2017-2018, this research led to a historic breakthrough: for the first time, 60 years since its discovery, an economically feasible solution was found for late wilt disease of corn in Israel. The successful treatment protocol is based on changing the cultivation method, changing the traditional irrigation method used in most corn growing areas in Israel, and the sophisticated integration of pesticide mixtures in a schedule adapted to key points in the development of the disease. This method can now be widely applied in commercial fields for the protection of sensitive corn varieties.

Late wilt disease in corn is caused by the fungus Harpophora maydis, which is found in the soil and seeds. It penetrates the plant and blocks the water supply to its upper parts. The disease, considered to be the most severe corn disease in our region, was first discovered in Egypt in 1960, where it still persists and causes serious damage. The disease is now reported in 11 countries. In Israel, it has existed for 40 years in the Upper Galilee, especially in the Hula Valley, and in the past decade, has spread to the south of the country. In heavily contaminated fields and in sensitive maize cultivars, the pathogen can cause 100% infection and total yield loss. The disease is characterized by a rapid wilt of the corn plant, which usually occurs two to three weeks before harvesting. In the past, attempts had been made to control the pathogen using different methods, including agricultural (balanced soil fertility and flood fallowing), chemical, biological, physical (solar heating) and plant compounds. Despite the potential of some of these methods, the only means applied in Israel to date to restrict the disease is the use of resistant corn varieties. However, in Egypt and Spain, virulent pathogen strains that threaten resistant maize cultivars have been found.

The research team led by Dr. Ofir Degani from Migal – The Galilee Research Institute and Tel-Hai College, funded and supported by Netafim Israel, the Extension Service of the Israel Ministry of Agriculture and Rural Development, and growers' associations, has recently led to a breakthrough development of historical significance. For the first time, 60 years since the discovery of the late wilt disease, an efficient and economically feasible solution has been found that can be used on a large scale to protect sensitive corn varieties in commercial fields.

This solution, published in December 2018 in the leading scientific journal PloS ONE, saves about 40% of irrigation costs and combines antifungal mixtures with different mechanisms to prevent resistance development. The new application was tested in field trials in 2017-2018 and included the injection to the irrigation system of  the substances Difenoconazole + Azoxystrobin (of which the commercial name is 'Ortiva-Top', manufactured by Syngenta, Basel ,Switzerland, supplied by Adama Makhteshim, Airport City, Israel), at intervals of 15, 30 and 45 days from sowing, or other fungicide mixtures. Savings in the deployment of irrigation lines was acquired by using a dripline for two adjacent rows (a row spacing of 50 cm instead of 96 cm), a row space that maintains the effective concentration of the fungicide in the soil. A recently developed real-time PCR-based molecular detection system showed that following the treatment of 'Ortiva-Top', the amount of pathogen DNA in the host tissue decreased to near zero levels. The successful treatments using 'Ortiva-Top' resulted in a 100% decrease in dehydration symptoms and a 100% increase in crop yield, together with an approximately 40% increase in crop quality (the yield classified as A class that had a cob weight exceeding 250 g). These results were also obtained in an alternative protocol– the replacement of pesticides based on 'Ortiva-Top' in the first application and the application of pesticides harboring a different mechanism of action in the second and third applications. A remote sensing evaluation of the efficacy of the treatments using a quadcopter equipped with a thermal infra-red sensitive camera carried out by Dr. Assaf Chen’s research team (Migal - Galilee Research Institute) supported the results and showed its effectiveness as a research tool for diagnosing infected fields.

These results are the fruits of a decade of research (since 2008), in which a fundamental understanding of the pathogen H. maydis and the generation and development of late wilt disease in Israel was established. During this period, new research methods such as sensitive molecular tests (PCR and qPCR) were developed in order to diagnose fungal virulence and in order to detect the pathogen inside the host plant tissue. In addition, a link was found to plant hormones that regulate the development of the pathogen. Complex field trials that were carried out annually over a full growing season (about 80 days) since 2009 led to this important discovery.
However, the work on late wilt disease does not end here. In the past two years, Dr. Degani's research team identified the presence of H. maydis in secondary hosts, such as cotton, watermelon and green foxtail (Setaria viridis), which could support the survival of the pathogen, developed an environmentally friendly biological control method to control the pathogen, and established a new bio-assay for examining soils suspected of being infected with the pathogen. These new findings, which are currently in the process of being prepared for scientific publication, are encouraging the continuation and enhancement of the research.

Curly top disease is caused by a complex of curtoviruses (family Geminiviridae), and it continues to plague tomato production in California. To better understand the etiology of curly top of tomatoes in California, polymerase chain reaction (PCR)-based methods were developed and used to characterize the curtoviruses involved, and to monitor for these viruses in the beet leafhopper vector, Circulifer tenellus. From 2002 to 2008, 86 processing and fresh market tomato fields in the Central Valley of California were surveyed for the incidence of curly top symptoms. Representative samples with curly top symptoms were collected from the surveyed fields, as well as from another 24 fields. The incidence of curly top symptoms in most fields ranged from trace (<1%) to low (1 to 5%); however, in 2002, 2003, and 2008, some fields had medium (5 to 20%) or high (>20%) incidences. PCR with general and species-specific primers was used to establish that the predominant species associated with...

The relationship between moisture content and carpogenic germination (CG) of Sclerotinia sclerotiorum sclerotia and the dynamics of sclerotial water imbibition were studied in a controlled environment. The study was conducted using laboratory-produced sclerotia from seven S. sclerotiorum isolates. The quantity and rate of water imbibition by three sizes of sclerotia was determined gravimetrically in silty clay, sandy loam, and sandy soils maintained at 100, 75, 50, and 25% of soil saturation and in distilled water. Smaller sclerotia imbibed water at a significantly faster rate (P = 0.05) than larger sclerotia in water and in soil at all saturation percentages. When buried in soil, small, medium, and large sclerotia were fully saturated within 5, 15, and 25 h, respectively, in all three soil types and moisture percentages. The effect of sclerotia moisture content on CG was evaluated on sclerotia maintained at 95 to 100, 70 to 80, 40 to 50, and 20 to 30% of their water saturation capa...

During spring 2009, lavender plants (Lavandula stoechas L.) showing a bright yellow mosaic of calico type and light stunting were observed in a commercial nursery in Liguria Province in northern Italy. Of 300 plants inspected, ~2% were symptomatic. Preliminary observations of leaf sap with the transmission electron microscope revealed bacilliform virus-like particles in three symptomatic plants, whereas no virus-like particles were observed in asymptomatic plants. The same symptomatic plants were tested by double-antibody sandwich-ELISA with polyclonal antisera against Cucumber mosaic virus, Potato virus Y, Tobacco mosaic virus, and Alfalfa mosaic virus (AMV). All three plants reacted positively against AMV antibodies, but not the other antibodies. A crude sap extract obtained from a single symptomatic plant, hereafter referred to as the Lst isolate, was prepared by macerating 1 g of fresh leaves in 4 ml of sodium phosphate 0.03 M, containing 0.2% sodium diethyldithiocarbamate, 75 m...

Aim: The aim was to assess the incidence, severity and symptoms of the leaf blight of taro. Methodology: A survey of 50 taro fields was conducted during the major cropping season of 2015 in 11 districts of the semi deciduous forest zone of Ghana. Disease incidence and severity were calculated and samples collected. Isolation, morphological identification and Koch's postulate of the associated pathogen was carried out at the Plant Pathology Laboratory of the CSIR-Crops Research Institute, Kumasi, Ghana. Results: Phytophthora colocasiae Raciborski, was identified as the causal pathogen of the leaf Original Research Article Adomako et al.; AJEA, 11(4): 1-7, 2016; Article no.AJEA.23806 2 blight disease attacking taro. The study revealed a high incidence and severity of the disease across all locations surveyed. Incidence ranged from 30% in the East Akim District to 92.5% in the Tano South district whilst severity ranged from 6.5% to 86.5% in the East Akim and Tano North districts respectively. Disease incidence and severity was significantly different (P < 0.05) across the districts surveyed. Symptoms of the disease included multiple circular spots on the leave surface, white mycelia on lesion surface; shot holes on affected parts and water soak beneath the developed spots. Conclusion: The current study revealed a high incidence and severity of the disease in the surveyed districts and has laid the foundation for extensive studies on the epidemiology of the disease in Ghana and the need to develop management strategies to reduce its impact.

Tomato plants can be infected by several diseases, among them, the early blight disease, caused by the necro-trophic fungus Alternaria solani is very dangerous. Plant growth promoting rhizobacteria (PGPR) are enhanced the plant growth and suppress plant diseases. The current study was conducted in a pot experiment to investigate the bio-efficacy antagonistic bacterial isolates as either individual or combination against tomato early blight disease. Disease severity and protection percent, morphological indicators as well as yield characters were recorded. In vitro antagonistic activity assay of PGPR against A. solani was estimated. Metabolic indicators of resistance in plant as response to induction of systemic resistance (ISR) were recorded. Our results indicated that, PGPR isolates were reduced the percent disease severity by 13.0 % and recorded highly protection percent by 84.3 %. The beneficial effects of the used elicitors were extended to increase not only the morphological characters (shoot lengths, root lengths and leaflet number/plant) but also the yield characters. All tested elicitors caused the marked significant increases in the photosynthetic pigments. PGPR isolates were exhibited the most potent effect in terms of the contents of chlorophyll a, b and the total chlorophyll (a + b) followed by plants treated with A. xylosoxidans (A3), B. subtilis (B1) and L. fusiformis (L2) in the infected plants, compared to the non-treated infected control. PGPR isolates were increased total phenol (56.15 mg/100 g dry wt.), free proline (1.435 mg/g dry wt.), total protein (1.198 mg/g dry wt.) and the activities of peroxidase (0.705 μg/100 g fresh wt.) and polyphenol oxidase (1.281 μg/100 g fresh wt.). All the tested treatments resulted in increasing the contents of indole acetic acid (IAA), Abscisic Acid (ABA), Salicylic Acid (SA), and Jasmonic acid (JA) compared with those of the infected plants. PGPR isolates' antifungal activity may be attributed to cell wall disruption of A. solani and the normal conidial development inhibition. Therefore, due to these outstanding properties of PGPR isolates as plant growth promoters and antifungal activity, this study could give insights for solving serious agricultural challenges and particularly in the treatment of A. solani invasion across the tomato plants.

Ramularia collo-cygni is the biotic factor responsible for the disease
Ramularia leaf spot (RLS) of barley (Hordeum vulgare). Despite
having been described over 100 years ago and being considered a minor
disease in some countries, the fungus is attracting interest in the
scientific community as a result of the increasing number of recorded
economically damaging disease epidemics. New reports of disease
spread and fungal identification using molecular diagnostics have
helped redefine RLS as a global disease. This review describes recent
developments in our understanding of the biology and epidemiology of
the fungus, outlines advances made in the field of the genetics of both
the fungus and host, and summarizes the control strategies currently
available.

Maize is a staple food crop which plays a great role in food security in Ethiopia. It is affected by many diseases which reduces yield. Mycotoxin contamination of maize grain (Zea Mays L.) is a global threat to safety both for human food and animal feed. Mycotoxins are secondary metabolites produced by fungi, which may be toxic or have other debilitating effects on living organisms. The major control methods are use of relative resistant or tolerant varieties mean that varieties with tight husk coverage, harvest on the time, proper storage and good crop management. An experiment conducted on experimental field of Jinka Agricultural Research Center to evaluate 12 improved maize varieties and one local check using Randomized Complete Block Design with three replications. The objective of the study was to select maize variety /varieties resistant/tolerant to ear rot. The variety BH660 and BH540 was highly resistant compare to the other tested varieties with the incidence of 19.00% and 14.66% and a grain yield of 3.70kg/plot and 3.79kg/plot respectively. The varieties BH543, Melkassa7 and BH661 were susceptible with the incidence of 64.00%, 50.13%, and 64.33% and their grain yields were of 3.37kg/plot,2.62kg/plot and 3.62kg/plot respectively. On the other hand BHQPY545 and local check were susceptible to ear rot but their yields were 4.05kg/plot and 3.84kg/plot respectively. This indicates that the local check and BHQPY545 were able to tolerate high disease pressure. Therefore, the variety BHQPY545 is recommended for mid land maize production areas of South Omo zone.

The efficacy of biofumigation with Brassica carinata pellets (BioFence) to control vegetative and reproductive structures of Phytophthora cinnamomi was investigated in vitro at different doses and temperatures. Biofumigation was effective in inhibiting mycelial growth (culture diameter) and chlamydospore and zoospore germination, and was lethal at 24 mg of pellet per plate (approximately 0.4 mg/liter). The 50% effective concentration values showed that efficacy of B. carinata pellets in inhibiting or killing the vegetative and reproductive structures of P. cinnamomi was maximum at 15°C and decreased as temperature rose to 25°C. However, the fungicide effect was independent of the temperature. In vivo biofumigation of Quercus cerris seedlings with BioFence confirmed efficacy by reducing the inoculum density (CFU/g) of P. cinnamomi, thus protecting the host from root infection. The use of BioFence provides an alternative to synthetic pesticides to control P. cinnamomi within disease m...

Abstract: Wilt is an important disease of brinjal crop causing significant reduction in yield. In present study, the pathogenic fungus was isolated from infected plant parts and identified based on morphological and cultural characters as Fusarium solani f. sp. melongenae. ...

The role of initial inoculum (yo), rate (r) of pathogen or disease development (infection), and period of time (t) that the pathogen and host populations interact during the cropping period is revisited in modeling plant disease epidemics. The importance of quantitative informations and the relationship between initial inoculum and the rate of disease development represent key elements for identification of the most useful disease models to be used. For effective Integrated Disease Management of monocyclic or polycyclic epidemics, temporal population growth models of plant disease epidemics (monomolecular, exponential, logistic and Gompertz population models) are presented. Sanitation and disease management principles (exclusion, avoidance, eradication, protection, resistance and therapy) are described. Finally, the integration of IPM practices, at the disease components level, with Lieberg’s Law of the Minimum is discussed.

The use of deep learning models to identify lessions on cotton leaves on the basis of images of the crop in the field is proposed in this article. Its cultivation in tropical regions has made it the target of a wide spectrum of agricultural pests and diseases, and efficient solutions are required. Moreover, the symptoms of the main pests and diseases cannot be differentiated in the initial stages, and the correct identification of a lesion can be difficult for the producer. To help resolve the problem, the present research provides a solution based on deep learning in the screening of cotton leaves which makes it possible to monitor the health of the cotton crop and make better decisions for its management. For this approach, Automatic classifier CNN will be used for classification based on learning with some training samples of that two categories. Finally the simulated result shows that used network classifier provides minimum error during training and better accuracy in classification.

... Francis P. Wong and Wayne F. Wilcox, Department of Plant Pathology, Cornell University, New York Agricultural Experiment Station, Geneva, NY 14456 Plasmopara viticola (Berk. &amp;amp;amp; Curt.) Berl. &amp;amp;amp; Toni., the causal agent of grape-vine downy mildew, is a highly destructive ...

Agricultural drones are one of the important innovations for increasing productivity of the crops in Indian agriculture field. The monitoring of the crops and the need for spraying pesticides and fertilizers at the correct moment and at the exact location of plants is an important parameter to increase the productivity of the crops. Unmanned Aerial Vehicle (UAV) can be used in agricultural sectors which will reduce the time and the hazardous effects that can cause due to the spraying of pesticides and fertilizers. This paper reviews briefly the implementation of UAVs for crop monitoring and pesticide spraying.

Deep Learning becomes the most accurate and precise paradigms for the detection of plant disease. Leaves of Infected crops are collected and labelled according to the disease. Processing of image is performed along with pixel-wise operations to enhance the image information. It is followed with feature extraction, segmentation and the classification of patterns of captured leaves in order to identify plant leaf diseases. Four classifier labels are used as Bacterial Spot, Yellow Leaf Curl Virus, Late Blight and Healthy Leaf. The features extracted are fit into the neural network with 20 epochs. Several artificial neural network architectures are implemented with the best performance of 98.59% accuracy in determining the plant disease. This was a great success, demonstrating the feasibility of this approach in the field of Plant Disease Diagnosis and high crop yielding.

Potato (Solanum tuberosum L.) belongs to family Solanaceae of order Solanales. Potato is one of the unique crop grown in the country having high productivity and supplementing food needs. Potato is rich in carbohydrates, proteins, phosphorus, calcium, vitamin C and vitamin A. The vegetable basket is incomplete without this king of vegetables, a sustaining force and a culinary delight. The power of potato is known for
sustaining million of lives by providing nutritious food in the time of war and hunger and also used as staple food in several countries of the world. The world annual production of potato during 2013 was 453.44 million tonnes covering an area of 19.92 million hectare with the productivity of 22.8 tonnes per hectare. Indian contribution to the world’s
production was 45.34 million tonnes from 1.99 million hectare area with average productivity of 22.8 tonnes per hectare (Anonymous, 2013).The high production potential per unit area, high nutritional value and great taste make potato one of the most important food crops in the world.

A new tospovirus isolated from naturally infected tomato plants grown in Nakhon Pathom province (Thailand) was characterized. Infected plants showed symptoms consisting of necrotic spots, necrotic ringspots and stem necrosis. This virus was detected using general antibodies that could recognize watermelon silver mottle virus (WSMoV), capsicum chlorosis virus (CaCV) and melon yellow spot virus (MYSV). However, it did not react with specific monoclonal antibodies (MAbs) to WSMoV and CaCV or a specific MAb to MYSV. The complete nucleotide sequences of S and M RNAs of the virus were determined. They were 3,023 and 4,716 nucleotides in length, respectively, and contained two ORFs in an ambisense arrangement. Sequence analysis indicated that amino acid sequence of the N protein shared 58.2%, 56.0% and 51.8% identity with those of CaCV, WSMoV and MYSV, respectively. The virus was experimentally transmitted by Thrips palmi and Ceratothripoides claratris. Based on our results, we conclude that this tospovirus isolate should be considered a member of a new species. The name tomato necrotic ringspot virus (TNRV) is proposed for this tospovirus.