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Identified a technique for early detection of olive tree leprosy.

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Identified a technique for early detection of olive tree leprosy.

Modern technology at the service of the olive tree.

Climate change, which has become increasingly evident in recent years, is having an impact on the health of fruit trees and the olive tree, like many other plant species, is under increasing attack from pathogenic insects, bacteria and fungi. Scientific research aims to anticipate the recognition of these diseases in order to reduce damage and preserve quantity and quality of the harvest. The research conducted by Dr Antonio Fazari on the recognition of olive tree leprosy, anthracnose, marks an important step forward in the fight against olive tree pathogens.

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What affects the health of an olive grove.

Adverse weather conditions, soil conditions, incorrect use of fungicides, insecticides or herbicides adversely affect the natural ability of the olive tree to resist pathogen attacks. Excessive heat is aggravated by insufficient water availability in the soil while excesses of cold are more damaging in spring and winter than in autumn. Lesions caused by the cold and micro-lesions caused by hail promote the penetration of the bacterium rogue agent and create the right environmental conditions for the development of fungal infections such as the so-called peacock's eye. In the environmental context developed over the last twenty-five years, an increased number of pathogenic insects, bacteria and fungi have been observed on olive trees. The presence of fungal diseases such as Leprosy or Anthracnose, Verticillium disease, Peacock's Eye or smallpox, Plumbago or Cercosporiosis, Fumaggina, Caries or Lupa and Root Rot, bacterial infections such as Rogna or Tuberculosis and phytopathogenic insects such as the Oziorrinco, the Punteruolo, the Tignola, the Black Louse, the Fleotribo and the Olive Fly have therefore been confirmed.

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Olive tree leprosy.

Anthracnose, commonly known as olive tree leprosy, is one of the most important fungal diseases affecting olive trees. Unlike peacock's eye, this disease doesn't affect the leaves but the olives. The fungus responsible for the infection attacks the drupes, which show dark necrotic indentations and fall to the ground or mummify on the tree. If left unchecked, leprosy can cause huge production losses of up to fifty percent; if crushed, drupes infected with the fungus produce a poor quality olive oil with high free acidity and a red colour. One of the main problems is detecting the disease early, giving the olive grower the chance to intervene early and limit the reduction in quantity and quality.

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The biological cycle of leprosy and defence strategies.

Infected fruit may fall early or mummify on the tree. At high humidity, reddish pustules form on the affected fruit, releasing conidia, the asexual reproduction form of the fungus that causes the disease, which are transported by the rain and act as inoculum for secondary infections. Several cycles of infection are thus initiated on the plant, also favoured by the typical rainy and cool autumn climate, which if not interrupted in time lead to a significant loss of production. A distinction must therefore be made between a latent primary infection, which is contracted in spring and remains asymptomatic until veraison, and a secondary infection, which affects drupes that have arrived healthy until veraison and which is much faster and more violent in degrading plant tissue. The mummies that remain attached to the olive trees act as an inoculum for the following year's infection, when spring temperatures favour the release of conidia and the maturation of the spores. The strategy for defending olive trees against the leprosy pathogen overlaps in many respects with the strategy used to defend plants against peacock's eye. It mainly involves choosing large planting distances appropriate to the vigour of the trees and pruning in order to remove all branches bearing mummified fruit, aerate the foliage and encourage foliar wetting during phytosanitary treatments.

Dr. Antonio Fazari's research on anthracnose or olive tree leprosy.

Dr. Antonio Fazari together with Dr. Bruno Bernardi, Dr. Giuseppe Zimbalatti and Dr. Souraya Benalia of the Department of Agriculture of the Università degli Studi Mediterranea di Reggio Calabria in collaboration with Dr. Oscar J. Pellicer-Valero, Dr. Juan Gómez-Sanchıs of Intelligent Data Analysis Laboratory Department of Electronic Engineering, ETSE, University of Valencia (Spain), Dr. Sergio Cubero and Dr. Jose Blasco of the Centro del Agroingenieria, Instituto Valenciano de Investigaciones Agrarias, Moncada (Spain) aimed to test the possibility of detecting this disease in its early stages, using hyperspectral images and advanced modelling techniques of Deep Learning (DL) and Convolutional Neural Networks (CNN). For experimental purposes, olives were artificially inoculated with the fungus; hyperspectral images (450-1050 nm) of each olive were acquired until visual symptoms of the disease were observed, in some cases for up to nine days. The olives were divided into two classes: 'control' inoculated with water and 'fungi' inoculated with the fungus. The method resulted in good accuracy, 91.8%, sensitivity, 96.88%, and lower but still reasonable specificity, 73.08%, due to false negatives in the first days after inoculation. From the fifth day after inoculation, accuracy, sensitivity and specificity reached 100%, when the damage on the olive skin was still minor and had a visual appearance of a small stain. The proposed analysis was therefore successfully tested and if applied in post-harvest operations, could ensure a reasonable and accurate control of olive anthracnose to safeguard the quality and commercial value of the olive and olive oil.

Bibliography:

Antonio Fazari et al, Application of deep convolutional neural networks for the detection of anthracnose in olives using VIS/NIR hyperspectral images, Computers and Electronics in Agriculture 187 (2021) 106252