Downy mildew explosion threatens Impatiens industry

The £40m Impatiens industry is under threat after an explosion of downy mildew has hit busy lizzies in parks and gardens following outbreaks at commercial nurseries this spring.

Impatiens industry under threat of downy mildew 'explosion' - photo Crown copyright - courtesy of CSL
Impatiens industry under threat of downy mildew 'explosion' - photo Crown copyright - courtesy of CSL

Growers are concerned that the consumer will be scared off buying busy lizzies.

The RHS has received scores of enquiries as the disease multiplied in the wet and mild summer weather and have advised gardeners not to replant Impatiens in the same ground for at least a year.

Growers controlled the disease with professional fungicides but symptoms emerged in garden centres and gardens later in the season.

The British Protected Ornamentals Association (BPOA) and the Stockbridge Technology Centre (STC) are investigating the extent of the problem in commercial nurseries and are urging bedding producers to send back surveys issued last month.

ADAS consultant Wayne Brough said: The disease has been found more on nursery sites this year, where before it emerged at garden centres. It has been worse than usual and started a lot earlier.

Oldham parks manager Steve Smith said busy lizzies were looking like shrivelled stumps in Oldham parks.

STC director of plant pathology Martin McPherson said resting spores are being seen for the first time appearing as blackened streaking in the stem, but he is not sure if it is a new strain as reported.

The pathogen responsible, Plasmopara obducens, first appeared in 2003, and it was believed to have come in on seed supplied from the US.

McPherson said it is not yet known whether the disease is now being spread via seed, soil, air or vegetatively and if it overwinters.

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