Late Blight Control – Date and Product Strategy Must be Correct!

Late Blight Control – Date and Product Strategy Must be Correct!

Germany, Bavaria; Bayerische Landesanstalt für Landwirtschaft

Institut für Pflanzenschutz; authors: Michael Zellner, Steffen Wagner, Bernhard Weber, Johann Hofbauer http://www.lfl.bayern.de/ips/landwirtschaft/12990/

 

This article (in English) provides very useful information and tables about the essentials in late blight control concerning the choice of product and the timing of the application. Tables of different fungicides, dates of application, a comparison of systemic and local fungicides are included. It explains the conditions for infestation, the function and modes of action of the fungicides. A selection of fungicides for first and later treatments is provided as well as optimum treatment frequency, dosage and prices.

Potato late blight control (Phytophthora infestans)

This article refers Potao late blight control in Germany achieved in 2007. A strategy is offered recommending products with different modes of action in order to prevent resistance development.

High infestation pressure occurred in 2007 and occurred mainly on leafs. The recommended strategy is to use first systemic or partial systemic treatment at the beginning of the infestation ensuring the protection of the foliage. Products based on contact activity are well suited if infestation pressure is low.

Intensive treatment (Stoppspritzung) to eliminate infections showed very good results maintaining spraying intervals and recommended dosage. The following should be observed:

-         Spraying intervals max.5 days

-         Application of full dosage of products local systemic effects combined with a spore killing product (selection):     Acrobat plus WG 2 kg/ha + Electis 1,8 kg/ha

                                                     Tanos 0,7 l/ha + Shirlan 0,3 l/ha

                                                     Valbon 1,6 l/ha + Ranman 0,2 l/ha + 0,15 FHS

                                                     Infinito 1,5 l/ha + Shirlan 0,3 l/ha

-         For the following treatment a product with good efficiency and rain persistence should be applied

-         For the continuing and final treatment (8-10 days before haulm destruction) spore killing products should be applied.

 

In order to prevent development of resistance alternating use of active ingredients is essential. An alternation of the products Valbon (no spore killing effects) and Infinito (a.I.: Fluopicolide and Propamocarb) with a different mode of action provides a good resistance strategy.

Infinito provides an antisporulant and translaminar effects providing protection to the stem and the growing leafs. Depending on infestation pressure the recommended dosage varies between 1,2 – 1,6 l in 7-10 days.

The table in the original document presents a selection of in Germany approved fungicides.

Column 1= product name; column 2 = recommended (approved) dosage; column 3= active ingredient name; column 4= active ingredient concentration; column 5= mode of action; column 6= distance to surface water (m) and reduction of drift; column 7= sensitive area requirements; column 8= price.

Fight against blight: independent blight fungicide trials summary – years 2003 to 2005

report-fight-against-blight-independant-blight-fungicide-trials-2003-2005-summary

This report presents independently generated data on the effectiveness and technical attributes of blight fungicides.

The BPC commissioned ADAS & SAC to carry out field trials in 2003, 2004 & 2005, located at ADAS Rosemaund and SAC Auchincruive. Only two trials were carried out at each site in each year. The P. infestans isolates used were all recent isolates at the time from the UK. All trials were carried out on small plots of the variety King Edward. To make comparisons of all possible combinations would be prohibitively expensive therefore the work reported concentrated on two protocols:

Early season fungicides (Protocol 1): Evaluation of fungicides applied very early in the development of the crop.  Two new fungicides at the time, Sonata and Tanos, were compared with three established fungicides often used at the start of programmes, Dithane NT, Invader and Shirlan.

Main season fungicide evaluation (Protocol 2): The performance of fungicides applied from the end of rapid canopy growth was compared because most of the new fungicides are recommended for this growth phase of the crop. In addition, this would allow their effectiveness in controlling tuber blight to be evaluated. The new fungicides Electis, Ranman TP and Sonata, were compared with the established products, Curzate M, Invader and Shirlan.

The fungicides tested gave a similar level of foliar blight control. The trials provided strong data for the relative fungicide efficacies against tuber blight.

 

Fungicide Resistance Action Group UK (FRAG-UK) Potato late blight: Guidelines for managing fungicide resistance

growers-advice-potato-late-blight-guidelines-for-managing-fungicide-resistance

This guide sets out actions to minimise the risk of resistance development to existing fungicides and new active substances for control of late blight.

The introduction in the late 1970s of the phenylamides brought a new dimension to blight control but there was a rapid development of resistance in the blight pathogen. This quickly brought about a change in the number of recommended applications. Of the current approved fungicides, resistance in Phytophthora infestans has developed only to the phenylamides, which was first identified in the UK in 1981.  The report provides information on the use of fungicide, the types and occurrence of fungicide resistance and how to reduce the risk of resistance developing in a pathogen population. A list of 12 fungicide groups, their mode of action and mobility, common name of active ingredient, product name, resistance risk and use is being presented. The Impact of new strains on fungicide use is also being addressed.

Managing fungicide resistance can be summarised as follows: where possible use a blight resistant cultivar, avoid growing large areas of highly susceptible cultivars, eliminate sources of blight (infected seed, ground-keepers and dumps), monitor local weather conditions, apply fungicides as protectants, select fungicides to suit local conditions, use mixed formulations of active ingredients with different modes of action or from a different fungicide families, or target specific products in blocks to appropriate growth stages, do not chase the epidemic with fungicides, burn off early if blight levels are significant and delay lifting until the haulm has been dead for at least 14 days.