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Recommendations on Resistance Management for Phenylamides

 
 

General Use Recommendations

(last updated in March 2020, changes are marked in bold face)
 

The general use recommendations for phenylamide-based products have remained unchanged since 1997. The key (“umbrella”) guidelines for product use are as follows (they have to be adapted to local requirements and resistance levels):

  • The phenylamides should be used on a preventive and not curative or eradicative basis.
  • For foliar applications, the phenylamides should be used in a pre-packed mixture containing an unrelated effective partner and used in a sound management program. Where residual partners are used, it is recommended to use between three quarters and full recommended rates. The phenylamide dosage in the mixture depends on its intrinsic activity and is defined by the respective company.
  • The number of phenylamide applications should be limited (two to four applications per crop and year, with a maximum of two consecutive applications). The application intervals should not exceed 14 days and may be shorter in cases of high disease pressure. If rates and application intervals are reduced, the total amount of the phenylamide fungicide used per season should not exceed that of the full rate, and the total exposure time should remain the same. The rate of the mixing partners should remain the same for both intervals.
  • Phenylamide sprays are recommended early season or during the period of active vegetative growth of the crop. The farmer should switch to non-phenylamide products not later than the normal standard application interval of the non- phenylamide product.
  • Seed treatment:
    • PA used as seed treatment is considered in general lower risk of resistance development.
    • However, foliar or soil drench applications of PA containing products in the previous crop can influence the sensitivity situation particularly in vegetable crops.
    • Careful planning of the crop rotation and the respective PA usage during the season is recommended in order to lower the selection pressure on the soil population of Pythium spp. Applying PA containing products in e.g. spinach, beans, cauliflower, can accelerate PA resistance for the following crop planting, e.g. corn. Cereals, rape or grassland as a previous crop do not negatively affect PA sensitivity.
    • For seed treatment, mixtures rather than straight phenylamides should be used whenever possible.
  • The phenylamides should not be used as soil treatments against foliar diseases. When solo formulations are made available for soil use, strategies must be implemented which prevent any possibilities for foliar applications.

Contact

Dr. Helge Sierotzki
Chair

Syngenta Crop Protection Münchwilen AG
WST540.1.94
CH-4332 Stein

Tel : +41 62 866 01 80
Fax: +41 62 866 07 63
helge.sierotzki@syngenta.com