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Poster: Biology & Disease Mgmt: Chemical Control


Relationship between fungicide dose and Asian soybean rust control
A. CHECHI (1), C. Forcelini (2), W. Boller (2), R. Roehrig (2), E. Zuchelli (2) (1) UPF, Brazil; (2) UPF, Brazil

The diseases affect the soybean crop yield, and the main one is the Asian soybean rust (ASR) and the control of the disease is mainly based on fungicides. The objective of this study was to verify if the use of 0 to 100% of the commercial dose of fungicide affects the control of the disease. The experiment was conducted in a growth chamber at UPF, in a completely randomized design with six replications. For this, the central leaflets of soybean plants (NS 5445 cultivar) grown in a greenhouse were collected. The solutions from 0 to 100% of the dose were prepared using two fungicides, one consisting of trifloxystrobin + prothioconazole and other azoxystrobin + benzovindiflupir. The leaflets were dipped in appropriate fungicide solutions and placed in gerboxes, where humid chambers were set up. In the next day, a suspension of Phakopsora pachyrhizi (50,000 spores/mL) was prepared, which was sprayed on the leaflets. The gerboxes were left in the dark for 24 hours at a temperature of 23°C. After this, they were placed on benches in a growth chamber with a photoperiod of 12 hours light/dark and constant temperature of 23°C. After 22 days incubated, the number of spores/cm2 was assessed. The controls without application of fungicides showed an average of 85.4 spores/cm2 (T+P) and 83.5 spores/cm2 (A+B). There was a reduction in the number of spores/cm2 when increases the fungicide dose. The ASR control depends on the fungicide dose in the spray solution.