Ramularia leaf spot effect on yield and fiber quality of cotton submitted to fungicide application

Abstract

Ramularia leaf spot (RLS) is the major cotton disease in Brazil and one of the main causes of crop yield reduction. The disease causes defoliation reduces photosynthetic capacity and causes premature opening of bolls. Due to the impact of RLS on the production of Brazilian cotton and the lack of scientific publications investigating the disease, the present work aims to evaluate the efficiency of fungicides in controlling disease and their impact on yield and fiber quality. Three field experiments were carried out during the 2014/2015 and 2016/2017 seasons in Planaltina, Federal District and Cristalina, Goiás. Experiments followed a randomized complete block design (4 blocks) and treatments consisted of the application of fungicides, plus a non-treated plot. The fungicide applications began preventively and were repeated every 14 days until six sprays had been completed. Severity of RLS was assessed and used to calculate the area under disease progress curve (AUDPC). Yield and cotton fiber quality were also evaluated. All fungicides had reduced AUDPC and obtained higher cotton yields in relation to the non-treated plot. Strobilurin-group fungicides (azoxystrobin, pyraclostrobin and picoxystrobin) showed low effectiveness when sprayed alone. The demethylation inhibitor fungicides (difenoconazole, epoxiconazol, tetraconazol and metconazole) were more effective than the strobilurins. The highest efficiency rates were achieved by application of pyraclostrobin + fluxapyroxad, pyraclostrobin + epoxiconazole + fluxapyroxad and fentin hydroxide. Disease severity affected cotton yield, causing losses from 14.8% to 31.7%. Resultant reductions in cotton fiber quality negatively affect the micronaire composition, altering the length, strength and uniformity of fibers.

INFLUENCE OF PROCESS PARAMETERS ON CELLULASE PRODUCTION BY Trichoderma viride (MTCC 800) EMPLOYING SOLID STATE FERMENTATION

“…Avoidable yield loss of 32.38% due to Alternaria leaf spot was reported with five sprays of propiconazole 0.1% with highest B:C ratio of 1.72 (Hosagoudar et al, 2014). Both kresoxim methyl (0.1%) and propiconazole (0.1%), sprayed thrice at 15 days interval starting from the first appearance were effective against foliar diseases in cotton and significantly increased the yield to the tune of 59.66 and 56.99 percent, respectively (Bhattiprolu, 2015).Seed cotton yield gain with (Tormen and Blum, 2019).…”

Ramularia leaf spot: PCR-based methods reveal widespread distribution of Ramulariopsis pseudogycines and limited presence of R. gossypii in Brazil

“…In Brazil, the disease was rst reported by the Agricultural Inspection and Defense Service of São Paulo in 1919 and was considered of secondary importance until the 90's 9,11 . Currently, RLS is the major cotton disease in Brazil, with up to eight spray applications of fungicide required to reduce its negative effects on yield and cotton ber quality 4,5,12 .…”