1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Early detection and prediction of powdery mildew of salad cucumber under polyhouse cultivation(Department of Plant Pathology, College of Agriculture , Vellanikkara, 2024-03-18) Athira, T U; Sainamole Kurien, PThe study entitled “Early detection and prediction of powdery mildew of salad cucumber under polyhouse cultivation” was conducted at the Department of Plant Pathology, College of Agriculture, Vellanikkara during the period from 2022-2023. The main objective of the study was to develop a mobile application for early detection of powdery mildew of salad cucumber and a prediction model for the disease based on meteorological parameters during the particular crop period.Symptoms are visible manifestations of disease endured by a plant and imaging techniques are used to detect a disease by identifying the symptoms at an early stage. Early detection of diseases is essential for minimizing economic loss and also managing the disease using biocontrol measures. Moreover, disease spread is faster in protected structures owing to reasons such as intensive monoculture and controlled conditions prevailing. Considering these, salad cucumber was chosen for this project as it is a popular vegetable crop in polyhouses in our state and powdery mildew is a disease which spreads very fast under favorable conditions.Hence, in the present project, visible imaging technique was used in combination with electronics and artificial intelligence tools to detect the presence of the disease at a very early stage of symptom development. The crop was sown in the polyhouse in February 2023 and the first incidence of disease was observed 47days after sowing. The images of healthy and infected leaves were taken during the crop period in a customized manner which were then processed and classified for enhancing the accuracy. As the next step, a disease detection model was developed using two different machine learning algorithms viz. DenseNet and Xception. The image pre-processing was also done through two techniques viz.ellipse and colour channel filtering. These two techniques were used to highlight the infected area in a particular leaf. The images were then divided in 70:20:10 ratio for train, validation and test datasets respectively. DenseNet model was used in the first part of mobile application where it assesses whether the leaf is healthy or not. So both healthy and infected leaf images were used to train the model to identify an infected leaf from healthy leaf. The DenseNet model achieved an accuracy of 90 percent in the detection process. Xception model was used in the second part of the application to assess the severity level of different infected leaves. A total of 2700 images taken during the study were grouped into seven classes from healthy to maximum severity level. The machine learning model was trained to detect the severity level and the model showed different level of accuracy for different severity levels of powdery mildew. The model could detect the presence of powdery mildew at the first infection stage itself in which only 10 percent of leaf area is infected with a test accuracy value of 82.05percent. Later these two models were jointly used for the development of a mobile application. The final application was developed in such a way that it detects the presence of powdery mildew at the earliest visible stage, assess the severity level and suggest management accordingly. Validation of the mobile application was also done using 120 images belonging to different severity levels and achieved an accuracy varying from 80-100 percent. Pearson’s chisquare test was done to check whether the accuracy of disease detection is significant rather than a random chance detection and found to be significant. In the second part of the study, the relationship between meteorological parameters that prevailed inside the polyhouse and severity of powdery mildew was assessed and a prediction model was developed for the disease. Accordingly, atmospheric temperature, relative humidity (RH) and light intensity were recorded daily at two time periods: at 7.30am and 2.30pm starting from 40 days after sowing.The temperature inside the polyhouse during the crop period varied from 25-28°C in the morning hours and 35-37°C in the afternoon hours. Throughout the period of powdery mildew infection, the average temperature inside thepolyhouse was nearly 30±1°C. The average RH inside the polyhouse varied from 63 to 74.5 percent.The light intensity varied widely, which ranged between 4800-6600lux. Percent disease severity (PDS) was calculated for 100 randomly scored leaves on daily basis. Correlation and regression analyses of meteorological data with PDS were performed where temperature showed a significant negative correlation and RH,a significant positive correlation with PDS. While, there was no significant correlation between light intensity and PDS. So based on the data on temperature, RH and PDSrecorded during the experiment, a prediction model of disease was developed using MATLAB software. An equation for the prediction of PDS also developed using multiple polynomial regression model. On validation the prediction model recorded an accuracy of 81 percent. Even though the android mobile application for early detection of powdery mildewis designed for salad cucumber, as the machine learning model uses colour filtering and ellipsing for image recognitionthis application can detect powdery mildew on any crop at first instance of its appearance. Farmers can easily detect the presence of the disease at its earliest stage of symptom expression. The algorithm used for this study can be further modified and utilized for other diseases alsoItem Ecofriendly management of major fungal foliar diseases affecting yard long bean in polyhouse(Department of Plant Pathology, College of Agriculture, Vellayani, 2019) Deepthi Nair, S; Sajeena, AThe study entitled ‘Ecofriendly management of major fungal foliar diseases affecting yard long bean in polyhouse’ was conducted at College of Agriculture, Vellayani and Integrated Farming System Research Station (IFSRS), Karamana during 2017- 2019 with the objectives to determine the major fungal foliar diseases affecting yard long bean grown in polyhouse; and their management using natural resources and ecofriendly methods. A survey was conducted in 15 polyhouses located at different parts of Thiruvananthapuram district, where yard long bean was cultivated. NS 621 was the most common variety of yard long bean cultivated in polyhouses. Powdery mildew (Disease Incidence (DI) - 100% and Per Cent Disease Index (PDI) - 60.70) and Diaporthe leaf spot (DI - 80% and PDI - 45.77) were the major fungal foliar diseases of the crop observed in these polyhouses. Five varieties of yard long bean viz. Lola, Vellayani Jyothika, Gitika (KAU Varieties), VS 50 (KAU pre release culture) and NS 621 (Namdhari Seeds Private Limited) were screened in the polyhouse at IFSRS, Karamana in completely randomized design (CRD) with four replications, to assess the natural incidence and severity of different fungal foliar diseases. The most susceptible variety to natural incidence of powdery mildew (PDI - 50.89) and Diaporthe leaf spot (PDI - 58.66) diseases was NS 621, whereas VS 50 was tolerant to powdery mildew disease (PDI - 11.11). In vitro evaluation of organic preparations viz, egg-lemon juice extract (10%) and sunflower oil (25 ml) + baking soda (10 g) + bar soap (10 g) + water (5 l), botanicals viz. fermented weed (Setaria barbata) extract (10%) and nimbecidine (0.5%), and non-hazardous compounds viz. potassium silicate (1%) and sodium bicarbonate (0.5%) against Diaporthe tulliensis by poisoned food technique in potato dextrose agar (PDA) medium revealed that fermented extract of S. barbata (10%), sodium bicarbonate (0.5%) and a combination of egg-lemon juice extract (10%) and fermented extract of S. barbata (10%) resulted in cent per cent inhibition of the mycelial growth of the fungus, which were further used for in vivo evaluation. Fermented egg-lemon juice extract (10%), potassium silicate (1%) as well as Psuedomonas fluorescens (KAU isolate) had no inhibitory effect on the mycelial growth of the fungus. A trial was conducted to assess the efficacy of selected treatments for the management of powdery mildew and Diaporthe leaf spot diseases in NS 621 in the polyhouse of IFSRS, Karamana in CRD with eight treatments replicated thrice. The plants sprayed with tebuconazole 50% + trifloxystrobin 25% (WG) (0.04%) (positive control) at 20, 40 and 60 days after planting (DAP) resulted in maximum control of Diaporthe leaf spot (PDI - 4.89) and powdery mildew (PDI - 1.22) diseases. Among the treatments, the combined application of arbuscular mycorrhizal fungi (AMF) (KAU isolate) @ 5g plant-1 at the time of planting along with the foliar application of fermented extract of S. barbata (10%) at 20, 40 and 60 DAP resulted in significant control of Diaporthe leaf spot (PDI - 11.35), whereas the combined application of AMF @ 5g plant-1 at the time of planting along with the foliar application of sodium bicarbonate (0.5%) at 20, 40 and 60 DAP resulted in significant suppression of powdery mildew disease (PDI -11.59). Soil application of AMF alone and foliar application of P. fluorescens (2%) had least effect in reducing the severity of both the diseases. Thus, the present study revealed that powdery mildew and Diaporthe leaf spot were the most important diseases of yard long bean in polyhouses of Thiruvananthapuram district. Soil application of AMF @ 5g plant-1 at the time of planting and foliar spray of fermented extract of S. barbata (10%) or sodium bicarbonate (0.5%) at 20, 40 and 60 DAP were the most effective treatments against Diaporthe leaf spot and powdery mildew diseases respectively, which could be used as a green technology to produce safe-to-eat yard long bean.Item Characterization and management of powdery mildew of yard long bean (vigna unguiculata subsp.sesquipedalis (L.) verdc.) under protected cultivation(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2018) Rahila Beevi, M H; Sainamole Kurian, PYard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verdc.) is believed to be selected and developed from cowpea (Vigna unguiculata (L.) Walp.) for its long, succulent pods which are used as a vegetable. In Kerala, it is one of the most preferred vegetables having very high amount of protein, iron, calcium, vitamin A, Vitamin C and dietary fibre. It is considered as a remunerative crop under protected condition owing to its high market demand. However, incidence of diseases is a major setback hampering the production of yard long bean under protected conditions among which, powdery mildew is the most devastating one. In this background, the present study was undertaken to characterize the pathogen causing powdery mildew of yard long bean and to formulate a management strategy for the disease under protected cultivation. Purposive sampling surveys were conducted in seven locations of Thrissur district and the disease severity varied from 1.67 to 67.33 per cent. The results of the survey indicated that the severity of disease was more during pod bearing and harvesting stage. Since powdery mildews are obligate parasites, characterization was done based on the microscopic observation of pathogen present on the leaves. The fungi produced hyaline, branched and septate hyphae. The conidiophores were erect and cylindrical on which conidia were born in chains. Variability was observed regarding conidia and conidiophore characters of powdery mildew collected from different locations, based on which the isolates were grouped into two viz., PM 1 and PM 2. PM1 type was observed in all locations except Vellanikkara. Based on the morphological characteristics of conidia and conidiophores, it was identified as Erysiphe polygoni. PM 2 type obtained only from Vellanikkara in which conidia and conidiophore characters were similar to Podosphera sp. which is very rarely reported on legumes. Hence, its identity was further confirmed as Podosphaera xanthii by molecular characterization. The rRNA-ITS sequence was deposited in NCBI Genbank database with accession number MH645799. This is the first report of powdery mildew of yard log bean incited by Podosphaera xanthii. In-vitro evaluation of 17 treatments including fungicides, biocontrol agents and botanicals by spore germination technique revealed that all the treatments caused cent per cent inhibition of conidial germination. For taking forward eight promising treatments to the field experiments, they were tested in-vitro on detached leaves by artificial inoculation of conidia from infected leaves. Based on the per cent leaf area infected, two systemic fungicides, one contact fungicide, two biocontrol agents and one botanical were selected for field evaluation. Field experiments were conducted simultaneously inside polyhouse and rain shelter to evaluate the performance of selected fungicides, biocontrol agents and botanicals against powdery mildew. Among the treatments, low disease severity of 4.33 per cent and 7.67 per cent was recorded in T1- difenoconazole and T2 – tebuconazole respectively in polyhouse and these treatments were statistically on par. In rain shelter also, T1- difenoconazole and T2- tebuconazole recorded low disease severity of 7.67 per cent and 10.67 per cent respectively. The performance of wettable sulphur at lower and higher concentration did not differed significantly. All the four non-chemical treatments were equally effective in managing the disease both in polyhouse and rain shelter. Correlation analysis between the meteorological parameters and disease severity revealed that per cent disease severity was negatively correlated with temperature and relative humidity both in polyhouse and rain shelter. Analysis of population of phylloplane microflora showed that, there was a drastic reduction in the population of phylloplane fungi and bacteria after spraying chemical fungicides which is an indication of the toxicity and non-selectivity of these chemicals. Survival ability of biocontrol agents sprayed on the leaves were studied and found out that both Trichodema viride and Pseudomonas fluorescens survived on the leaves for seven days. Residue analysis of difenoconazole, the most effective chemical fungicide revealed that the compound with initial deposition of 0.21 mg kg-1 dissipated to 0.09 mg kg-1 after seven days in polyhouse whereas, the residue after seven days in rain shelter was 0.19 mg kg-1. The faster degradation of the chemical inside polyhouse may be attributed to the higher temperature prevailed during the experiment. Evaluating the results various experiments in the present investigation, it was found that, even though chemical fungicides provided best disease control, considering their toxic effect on beneficial non target microflora on the phylloplane and the residue left on edible pods, biocontrl agents such as Trichoderma viride and Pseudomonas fluorescens which exhibited consistent performance with moderate disease control and sufficient survival on the leaf surface would be ideal to control powdery mildew of yard long bean if applied at right time. Moreover, frequent application of systemic fungicides with single site action can result in the development of resistant strains of pathogens. So such chemicals should be adopted only if the disease severity is very high and cannot be managed with biocontrol agents.Item Major diseases affecting rubber and Its control measures adopted by small growers of Vaikom taluk(Department of Plantation Crops and Spices, College of Agriculture, Vellayani, 1992) Sreedharan, A P; Sreekantan Nair, GThe major diseases affecting rubber in Vaikom taluk were powdery mildew, pink and abnormal leaf fall. Powdery mildew was more serious and infected about 99 per cent of the holdings surveyed. Dusting of sulphur at the time of refoliation can control the spread of the disease. Use of the chemical at the recommended dose was not adopted by the growers. This can be the main reason for the spread of the disease. Infection of pink disease was not so serious in the surveyed area. About 10.7 per cent of the trees were seen infected. Detection of the diseses at the early stages of infection and treatment of the trees was more important in the control of pink. It was obvious that the farmers knowledge in plant protection techniques were poor. No grower was seen adopting thiride treatment against pink though it was recommended as effective to Bordeaux paste. Lack of awareness of growers can be the main reason. Abnormal leaf fall was the least serious among the three diseases. The clone RRII 105 showed average tolerance to the disease and that can be the reason for the mild infection of the disease in the surveyed units. The study showed extension activities among the growers were highly inadequate. RRII 105 being the main clone, the leaf retention during monsoon was satisfactory even without prophylactic spraying. Therefore, prophylactic spraying was not seen as generally accepted practice among the growers of Vaikom taluk. Powdery mildew disease was very common in the surveyed units. But, many of the growers were neglecting it. All clones were seen infected with the disease. Repeated dusting of sulphur mixed with talc can control the infection effectively if sprayed at bud break. Four to six rounds of dusting should be done for the control of the disease. Extra weeding in plantation become necessary due to leaf fall and hence maintenance cost is higher. Unavailability of plant protection equipments was another difficulty faced by the growers. To overcome these difficulties disease tolerant clones may be planted in future. Moreover, the extension methods are to be strengthened to educate the growers about the diseases and its timely control.