Ramularia leaf spot: an emergent disease of cotton in Brazil

Abstract

Originated from the semi-arid highlands of Mexico, upland cotton (Gossypium hirsutum L.) accounts for more than 90% of world cotton fiber production. Intensively cultivated in Brazilian Cerrado since the early 1980s, the wet and warm environment of the region favors epidemics of fungal diseases such a Ramularia leaf spot, which emerged as the main disease of cotton cultivated in an area as large as one million hectares. Fungicides remain as the only resort to effectively control the disease and up to eight sequential sprays may be needed during the season. Research to improve disease management has been conducted during the last two decades including cultural, genetic, chemical and biological control methods. In this review we summarize current knowledge of the disease and the main findings and gaps on disease epidemiology and management and discuss on future direction towards a more sustainable management of a disease of greatest concern to cotton farmers in Brazil.

Dual functionality of Trichoderma: Biocontrol of Sclerotinia sclerotiorum and biostimulant of cotton plants

“…Since 1990s, the cotton growing area has dramatically expanded throughout the savannah Central-West region of Brazil (known as biome 'Cerrado'), mainly due to breeding efforts for developing locally adapted high-yielding cultivars and improving agronomic practices (Morello et al, 2015;Silva Neto et al, 2016;Barroso et al, 2017;Silva et al, 2019). As a result, the cultivated area in the Mato Grosso State has increased by approximately 1,500% in the last 30 years (ABRAPA -Associac ̧ão Brasileira dos Produtores de Algodão, 2021).…”

“…Currently, the Mato Grosso State is responsible for approximately 71% of the Brazilian cotton production, following an integrated cropping system with soybean and corn (Silva et al, 2019; IMEA -Instituto Mato-Grossense de Economia Agropecua ́ria, 2021). According to Meyer et al (2020), S. sclerotiorum is endemic in approximately 27% of soybean production areas in Brazil, and 87% of cotton growing areas in Mato Grosso, in which cotton is cultivated as a second crop after soybean crop (IMEA -Instituto Mato-Grossense de Economia Agropecua ́ria, 2021).…”

Identification of Cotton Leaf Lesions Using Deep Learning Techniques

“…Data from the official Brazilian government organ reveal that in 2019/2020, a yield of 28.2 million tons of cotton were produced from some 17 million hectares [ 3 ]. Despite the continental size of Brazil, its cultivation is concentrated in the states of Mato Grosso and Bahia, hot and humid regions where intensive cultivation and large technological investment must overcome climatic conditions which favor epidemics of fungal diseases, especially the ramularia leaf spot [ 4 ].…”

“…The adoption of conventional strategies for the control of pests and disease (treatment of the seeds, selection of resistant genotypes, control of the density and period of the year for planting, crop rotation and the use of biological agents), it was not enough. The only resource capable of effectively controlling the attack of pests and diseases is the preventive application of agrochemical products such as insecticides, acaricides and fungicides [ 4 , 11 ].…”

BRS 372 and BRS 416: high-yielding cotton cultivars with multiple disease resistance

“…In this scenario, diseases previously considered secondary or new diseases, e.g., Ramularia Leaf Spot (RLS), caused by the fungus Ramulariopsis pseudoglycines, can become epidemic. The latter cotton disease has a high economic relevance since up to eight fungicide applications per season are required to control it in a production area of more than 1.000,000 hectares (Silva et al 2019).…”