Frogeye leaf spot, the causative agent of which is the fungus Cercospora sojina, causes great losses to soybean crops, primarily in Argentina. The experiment, conducted in laboratory and acclimatization chamber, aimed to check the effect of different concentrations of inoculum of C. sojina on the intensity of Frogeye leaf spot in soybean leaflets. The used concentrations of conidia were 10x10³, 20x10³, 30x10 40x10³, 50x10³ and 60x10³ conidia.mL-1, with and without the presence of a spreader. After the inoculation of conidia by spraying on soybean leaflets, plants were maintained under 48-hour leaf wetness. After this period, the plants remained in an acclimatization chamber at 25 ºC for 15 days. The severity, number and diameter of injuries were evaluated. The concentration of 35,000 conidia.mL-1 with the presence of the spreader generated a disease intensity that enables the rapid and accurate quantification of the disease and can be used in future research.
Spreader; conidia; severity; Glycine max
