EuroBlight, the European network of scientists and other specialists working on potato early and late blight, has updated its efficacy tables for the control of late blight (Phytophthora infestans) and early blight (Alternaria solani) in potato and tomato for the 2016 field season. The ratings for control of leaf and tuber blight are based on unbiased EuroBlight trials carried out over multiple years and at multiple locations in Europe. All other ratings are based upon the expert knowledge of EuroBlight members.
Late blight caused by Phytophthora infestans is the most important foliar disease in the cultivation of potatoes. The crop needs to be protected from P. infestans by spraying fungicides regularly during the growing season. It is important to use fungicides that effectively protect leaves against this disease. A whole range of fungicides are registered in Europe. Each fungicide has its own mode of action, efficacies and other characteristics. The EuroBlight table was set up to provide an overview of the value of each characteristic. Until 2007, the ratings were based on judgements made by independent researchers and experts from agrochemical companies. Since 2008, the ratings have been based upon common trials.
Multiple years and locations
To evaluate the effectiveness of fungicides, harmonised protocols are agreed upon. The ratings of fungicides for leaf blight control for the EuroBlight table are calculated when field experiments are carried out over two years in three European countries. Each year from 2006 to 2015, at least three experiments were carried out. In total, 31 field experiments were set up to compare the fungicides’ effectiveness against leaf late blight by measuring the protection of leaves resulting from the application of a fungicide in a standard 7-day spray schedule (this standard spray schedule does not necessarily correspond with the label recommendations). The protection originates from the protectant and/or curative properties of the active ingredients. In addition, during the rapid growth phase of the crop also the protection of new growth can contribute to the effectiveness of the fungicide for leaf blight control. Dose rates were the highest preventative doses registered in Europe. The results of the trials were used to re-evaluate the effectiveness of fungicides to control potato late blight.
A similar approach was later adopted for tuber blight control and recently also for early blight control. Tuber blight ratings are now also based on EuroBlight trials. The first ratings for early blight control based on EuroBlight trials will become available in 2017.
The ratings of the other characteristics are decided by the EuroBlight experts (independent scientists and representatives from the crop protection industry) on the basis of available data. These characteristics are:
- Protection of new growth: the ratings for the protection of new growth indicate the protection of new foliage due to the systemic or translaminar movement or the redistribution of a contact fungicide. New growth consists of the growth and development of leaves present at the time of the last fungicide application and/or newly formed leaflets and leaves that were not present.
- Protection of stems: effective control of stem infection by either direct contact or via locally systemic activity.
- Mode of action:
Protectant: spores killed before or upon germination/penetration. The fungiide has to be present on/in the leaf/stem surface before spore germination/penetration occurs
Curative: the fungicide is active against P. infestans during the immediate post-infection period but before symptoms become visible
Anti-sporulant: P. infestans lesions are affected by the fungicide decreasing sporangiophore formation and/or decreasing the viability of the sporangia formed.
- Rainfastness: a fungicide is considered rainfast after application if it has adequately dried or has been absorbed by plant tissues so that it will still be effective after rainfall or irrigation.
- Mobility in the plant: contact, translaminar or systemic.
- Year of introduction: the year the fungicide was introduced in Europe.
The EuroBlight fungicide rating tables are widely accepted as the standard within Europe and beyond by independent scientists and fungicide producers. The rating are the most important basis for consulting and decision support on the disease control for potato growers in Europe.