VEGETABLE GARDENING IN DENTDALE

 

PESTS AND DISEASES
 

Damping Off


A sign of damping off
 A watering of Cheshunt compound will help.


Succumbed to damping off

 The pictures of the seedling shows the effect of damping off. It’s dead! Damping off is caused by any one of several fungi which thrive in damp, poorly ventilated conditions. The incidence of damping off can be reduced by using a well drained seed compost, that is, one with a proportion of sharp sand (see ‘compost’ on the gardening home page). Over watering reduces the oxygen supply to roots and this encourages damping off; keep seed compost moist but not saturated. Cleanliness helps too; clean pots or seed trays and sterile seed compost. This later requirement is hard to achieve if one is using home-made seed compost although my recent experience is that damping off has been no worse with home-made compost than with a purchased product and germination rates are much improved. Seedlings bunched together also seem more prone to damping off so a little time spent sowing thinly is worthwhile and it makes pricking out easier too.

Sometimes a precursor to damping off is the appearance of tiny white fibres of fungal growth radiating from a pinhead sized point on the surface of the seed compost or, with almost certain fatal consequences, from around a seedling stem. An occasional watering with a Cheshunt Compound solution or other copper-based antifungal treatment will help prevent damping off but in Dentdale’s  persistently high humidity ( It’s 81% as I type) it’s a difficult nut to crack.

White Blister

This morning's BBC News (27/11/08), included an item lamenting the UK's declining reserve of mycologists.  These are the experts concerned with fungi.  It seems we only have eight remaining in the UK of whom four are due to retire shortly!  Bad news!  Developments in medicine and even engineering depend upon them.

Whether this explains the appearance of White Blister on my vegetable plot or not I can't say, but gardeners should be concerned, especially as climate change for us seems to mean warmer, damp conditions.  Ideal for fungi!

White Blister affects brassicas (the cabbage family) and Brussels Sprouts in particular.  Certainly the recent appearance of White Blister on my vegetable patch confirms this.  The sprouts are noticeably affected whilst the immediately adjacent sprouting broccoli is not.  White Blister is a very appropriate name and adequately describes what you can see.  The blisters are about 3 to 4 mm diameter, appear in clusters on the underside of leaves and on the outer leaves of the sprouts themselves.  Fortunately, the remainder of the sprout is not affected and my crop has been both large and edible.  However, this may be because the infestation arrived quite late in the plant's development.  An earlier infestation might have done more damage.

So, what does one do about White Blister?  Well, in my case, this year,  nothing.  There are not many sprouts left to harvest so I'll just live with it.  However, I must be very careful not to spread the spores by putting the leaves of the spent plants on my compost heap – nor even the kitchen waste containing the affected outer leaves of the sprouts,

As for next year, I'll be on my guard and if I spot the beginnings of an infestation, I'll try a fungicide spray and take care to wash the harvested sprouts thoroughly.  If these mild, wet conditions continue, I expect we will see more fungal infestations like Club Root and White Blister so I guess the message is to encourage your children/grandchildren to qualify as mycologists; there's clearly a gap in the labour market.

 

November 2008


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