Project report: Independent variety trials

project-report-independent-variety-trials-2005

Varietal performance for 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 report presents a comprehensive summary that covers Project Aims, Work Undertaken and Findings (results on Susceptibility/resistance for 2005 are summarised in a table and rated on 1 (Low) – 9 (High) for resistance to disease, pest and defects) and conclusions.

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.