Potato Yield Increases Due to Fungicide Treatment in Argentinian Early Blight (Alternaria solani) and Late Blight (Phytophthora infestans) Field Trials During the 1996-2005 Seasons

Abstract

The effect of fungicides on potato yields in separate early blight and late blight trials during the 1996 to 2005 growing seasons at the INTA Balcarce experimental station was determined. Potato cultivars Pampeana INTA were used for early blight trials while Kennebec ones were used for late blight trials. A randomized complete block design with four replications was used in all trials. The fungicides Folicur 25EC at 0.5 liter/ha and Brestan 60WP at 0.5 kg/ha were tested in early blight trials while Dithane M80WP at 2.5 kg/ha and Ridomil Gold 68WP at 1.25 kg/ha were tested in late blight trials. Early blight infections were rated using a 0 to 50 a rating scale. Late blight severity was rated using a disease index of 0 to 5. Potatoes were graded into two categories, marketable (> 60 g) and undersize tuber “seeds” (< 60 g), and then weighed. Data was subjected to analysis of variance. Early and late blight symptoms were present every season. In early blight trials, the efficacy of the systemic fungicide Folicur 25EC was greater than that of the non-systemic Brestan 60WP. The average yield increase due to fungicide treatment during the ten-year period was 22.4% for marketable and 17.9% for total yield. In late blight trials the efficacies of Dithane M80WP and Ridomil Gold 68WP were similar. The average yield increase due to fungicide treatment during the study was 41.23% for marketable and 33.85% for total yield. Accepted for publication 23 October 2006. Published 2 February 2007.