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Overall Disease Situation

Imported seed is responsible for large race variability. Varieties in use are quite susceptible. Sources of inoculum are almost year round. There are two crops per year (fall and spring). Fall crop has more severe disease incidence. Large race variability (A2). Since early 90’s there is more incidence both on foliage and tubers.

Crop Losses

Variable, both from foliage and tubers. Late Blight is the most important disease affecting the crop.

Farmer Practice in Disease Management

Calendar spraying with protective and systemic fungicides. Fall crop uses more than 10 applications. Spring crop uses half of those. Early planting in the fall reduces the incidence. Delay harvest and vine killing.

Fungicides Being Used Against Late Blight

Mancozeb, Chlorotalonil, Cimoxanil, Acrobat, Previcur, Melody, Tin.

Physiological Races Recorded

Large variation is reported in a published paper (1).

Mating Types

A2

Metalaxyl Resistance

Most isolations.

Level of Disease Forecasting

Yes, Blitecast being validated.

Molecular Markers Being Employed For Pathogen Population Characterization

From isolations sent to outside the country collaborators.

There has not been a study on comparative aggressiveness of new Vs. old population done.

There is a variable relative importance of tuber blight.

On-going Potato Late Blight Research

Disease forecast validation, fungicide evaluation, variety breeding. MIP program being implemented for validation.

Disease Risk and/or Major Needs

Adapted sources of resistant germplasm.

Literature cited

(1) Deahl, K., Pagani, C., Vilaró F., Cooke, L. 2003. Characteristics of Phytophthora infestans isolates from Uruguay. European Journal of Plant Pathology. 109: 377-381.

Contact: F. Vilaro, D. Maeso (INIA). Email: fvilaro(at)inia.org.uy, dmaeso(at)inia.org.uy