This leaflet informs you how to use phenylamides fungicides in the context of resistance in France

phenylamide-en-2008-projet1

 SRPV / Arvalis – Institut du Végétal

We can demonstrate that there is a development of A2 type strains of potato blight and strains resistant to mefenoxam (metalaxyl-m) but the two phenomena are not linked.

So, the recommendations are:

- uses of phenylamides only before 1^st of july;

- maximum 2 products with Phenylamides;

- to apply registrated dose with Eperon pepite (mefenoxam + mancozeb), Epok (mefenoxam + fluazinam) and Trecatol (benalaxyl + mancozeb);

- no application with potato blight presence.

These recommendations are given from a network of trials of regional ministry services and French institute Arvalis institut du Végétal

Résumé français

Compte tenu des phénomènes de résitance de souches de mildiou de la pomme de terre en France, les recommandations d’utilisation des fongicides de la famille des Phénylamides sont très précises.

For Phythopthora infestans control it is recommended to choose open sides, with row width of 0,75 m and to avoid areas with high humidity. Pregermination will ensure a growth advantage of about 2 weeks. This can produce additional yields of 10 – 20% compared to cost of 90 – 140€/ha and year. Different varieties should be cultivated using the vertical resistance at the same time to reduce the overall risk. Copper products are the most promising alternative (cost efficient; postponed infestation; increasing yield up to 20%) to fungicides in organic farming. Copper products are preventive measures and used before first signs of infestation, a better control using low dosage in short intervals is achieved, small reductions of infestation increase yield about 10 – 20%, only be used under conditions of optimal nutrient supply. In warm humid weather conditions weekly spraying, in dry conditions less often (dosages of 300 – 500 g/ha copper).

The Colorado Potato Beetle has developed resistance to all commonly used insecticides. With SIMLEP DSS a temperature-driven DSS (consisting of two modules) has been elaborated for integrated pest management. SIMLEP 1 is a regional forecasting model for the first occurrence of hibernating beetles and the start of egg laying. SIMLEP 3 is a field–specific model forecasting the occurrence of the developmental stages of L. decemlineata.

The SIMLEP DSS contributed to an earlier application of insecticides (c. 10-14 days) and therefore no longer linked to late blight control. The control efficiency of conventional as well as biological insecticides is higher due to a treatment on the most susceptible larval stages of L. decemlineata. From 1999 to 2004 SIMLEP 3 was validated in Germany, Austria, Italy and Poland and is in large scale use there. In about 90% of cases SIMLEP 3 correctly predicted the periods of maximum egg laying and young larval occurrence, which are the optimal periods for field assessments and treatments with conventional and biological insecticides.

The project (sites with ls, sL, uL) is aiming to reduce the application of copper-containing pesticides by introduction of a blight forecasting system based on meteorological parameters. Primary stem infections should be reduced by seed treatment with copper fungicides (Cuprozin fluid (copper hydroxid), Copper protein and SPU 2100; all 120g/ha correlating to 48g Copper/t tuber) thus to postpone the beginning of the blight epidemic as well as the start of spraying. The first results showed a general reduction of stem infections in one Cuprozin variant of more than 80%.

To achieve best efficacy with reduced amounts of fungicides controlling secondary infections on the foliage, copper amounts and spraying intervals should be adjusted to the infection pressure. Field trials were carried out using the fungicides Cuprozin fluid, Funguran (copper oxychlorid) and SPU 1010 (in authorisation process) based on termination by the potato blight forecast system OKO-SIMPHYT 1+3. On the sL site the results showed a reduction of the secondary infections in all different control strategies.

Independent Variety Trials for Disease Suscetptibility 2005

Susceptibility to blight, black dot, black scurf, silver scurf, skin spot, common scab, powdery scab, blackleg, dry rot, potato cyst nematodes and other damages 

To comply with national and European Community legislation for marketing seed potatoes, varieties must be placed on the official National List (NL) of a Member State, which is then automatically entered on to the Common Catalogue (EC National List). Part of the NL testing involves assessing a new variety for Value for Cultivation or Use. In the UK, this testing is largely concentrated on assessing varietal performance for susceptibility to diseases, pests and important tuber quality characteristics. This 28-page experimental report describes tests conducted on 4 varieties undergoing their 2nd year of UK NL testing, 7 varieties which had completed UK NL tests and 5 Common Catalogue varieties. The above varieties were tested against foliage late blight, black dot, black scurf, silver scurf and skin spot. The Common Catalogue varieties were also tested for susceptibility to common scab, powdery scab, blackleg, dry rot, potato cyst nematodes, external (splitting) and internal (bruising) damages.

The document shows pictures of different machinery that may be used for mechanical weed control. Prices in Danisk kroner (7,45 Danish kroner = 1 Euro) are given as well as links to companies manufacturing or selling the machinery. The document may be found at www.planteinfo.dk by following the menu path  Afgrøder > Kartofler > Mek. Ukrudtsbekæmpelse > Redskaber

The resistance profiles of potato varieties towards Phytophthora infestans (leaf blight and tuber blight), tobacco rattle virus and potato mop-top virus are shown. The information is derived from the official Danish list of potato cultivars, which is published at www.planteinfo.dk . It may be found at this website by following the menu path  Afgrøder > Kartofler > Sorter

The uptake of nitrogen increases op to 6-11 % by placing the slurry in the ridge compared to normal spreading of slurry. A frequent problem in organic potatoes is low content of dry matter in the tubers, due to early wilting and immaturity caused by potato late blight. Pre sprouting promote early growth, but fertilizers should also be available early in the growth period. Precise supply of fertilizers in organic potato growing can increase plant vigour, yield and quality. The document shows the constraints and benefits by using broad spread and placed slurry. The nitrogen uptake increased op to 6-11 %, when the slurry was placed compared to normal spreading. There was a tendency that the fraction of large tubers was higher when the slurry was placed.

Production of organic ware potatoes is described in details for e.g. pre-sprouting, planting, fertilization, harvesting and storage. The growing instructions are updated on a regular basis. There are links to e.g. legislation, descriptions of pests and diseases etc.