Citrus leprosis: development and validation of rating scale for severity evaluation

• Grant number: 19/20217-0
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): December 01, 2019
• Effective date (End): November 30, 2020
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal researcher: Daniel Júnior de Andrade
• Grantee: Marcelo Eduardo Mechi
• Home Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

Citrus leprosis is one of the most important diseases for citriculture in tropical and subtropical regions of the American continent. The disease is caused by the Citrus leprosis virus (CiLV) being transmitted by mites of the genus Brevipalpus. In Brazil, the disease is present in all of the citrus producing regions, having the Brevipalpus yothersi Baker (Acari: Tenuipalpidae) mite as its main vector. For severity evaluation of citrus leprosis on orchards it is mainly used the scale proposed by RODRIGUES (2000). This scale consists of grades for citrus leprosis severity ranging from zero (0) to five (5) but, although widely used, it has never been statistically validated. The objective of this paper will be to validate the scale proposed by RODRIGUES (2000) under field conditions, if this scale presents unacceptable errors, propose a new scale adapted to obtain accurate and reproducible results. The experiments are being conducted in the municipality of Taquaral, São Paulo State, Brazil, where there are 3 plots of sweet orange Citrus sinensis (L.) Osbeck. In the 3 plots, the presence of citrus leprosis was visually confirmed and each area shows contrasting symptoms of the disease. In each field will be sampled at least 100 plants. From these 100 plants, ten plants will be randomly selected, and their heights, widths and spacings will be measured and taken into account to then estimate the average volume (m³) of the plants' canopy. The plots are being conducted based on the conventional management system. The evaluation of the presence, absence and severity of leprosis symptoms in citrus plants present in each field will be performed by five evaluators, who will be professionals with experience in this activity or who have been previously trained. (AU)