Monitoring metalaxyl-M sensitivity of Downy Mildew infection of Impatiens


The Problem:


Early and widespread introduction of a metalaxyl-M resistant strain of the pathogen responsible for impatiens downy mildew infections in commercial production in 2011 meant that the disease proved difficult to control. The proactive management decisions made by the industry regarding production of cutting raised plants in 2011 seem to have minimised the risk of infections by the metalaxyl-M resistant strain of Plasmopara obducens as no infection caused by this strain were detected during 2012 (PO 011) or 2013 (PO 011a); in 2013 no downy mildew infections of impatiens were reported. However the risk of infection by this strain still remains. This small scale project aims to continue the monitoring carried out in 2012 and 2013.


Benefits to industry:


In the UK, the annual retail value of the impatiens crop was estimated to be £40m prior to 2011. The outbreak of downy mildew in 2011 demonstrated that the disease has potential to destroy whole-site annual production as well as undermine consumer confidence in this commercially important product.

Prompt (up to 10 days after sample receipt) and widespread (sample originator and through the HDC a wider network of growers) reporting of the metalaxyl-M resistance status of any infections occurring during the project would allow growers to ensure that spray programmes used will be effective in minimising losses that may result from any outbreaks.
Project code:
PO 011b
01 March 2014 - 31 October 2018
AHDB Horticulture
AHDB sector cost:
Project leader:


PO 011b_Report_Annual_2015 PO 011b_Report_Annual_2016 PO 011b_Report_Final_2018 PO 011b_Report_Annual_2014 PO 011b_GS_Annual_2014

About this project

Aims and objectives:
Project aim(s):
Provide a mechanism for metalaxyl-M resistance screening in commercially grown impatiens in order to inform selection of fungicide programmes and also to monitor possible spread within outdoor planting displays.
This small scale project aims to continue the monitoring carried out in 2012 and 2013 to provide growers with:-
1. An early warning system for identifying the presence of metalaxyl-M resistance, in order to assist with decisions on suitable spray programmes.
2. Guidance as to the prevalence, persistence and geographical distribution of the metalaxyl-M resistant isolate compared to the metalaxyl sensitive isolates in the wider environment.