POLYTUNNEL GROWING – BEATING THE BLIGHT
When I first started growing under cover, I remember a large row of tomatoes being taken out by the dreaded blight. It swept through the plants in a couple of days and before I knew it the remainder of the harvest was ruined. This airborne disease is caused by warm, wet weather and although tomatoes and potatoes planted outside will be very vulnerable in a soggy summer, polytunnels can be equally as susceptible. Once you have the organism on your land then it just takes the right humid weather conditions for it to strike again. Having tried many different methods of prevention and socalled cures over the years, I have found a few effective methods.
It is much easier for blight to pass from the leaves of one vulnerable plant to another if they are situated in rows or blocks all together. If they are not, and there is an array of different types of produce instead, then it helps to stop the disease spreading.
This is important in a polytunnel, particularly during summer, so keeping doors or vents open overnight during the balmy middle of summer will help a great deal.
Pick off lower leaves
If you see the odd leaf with a brown mottled patch (the tell-tale sign of blight), remove it and dispose of it well away from your veg patch. Do not compost. This is all I have to deal with now — the odd leaf affected here and there which doesn’t impact on the plant or the quality of the fruit at all.
A word on watering
It is recommended that to avoid blight you water your plants from below to avoid getting moisture on the leaves and that watering in the morning is preferable to the evening. I go with the latter, but personally use an overhead sprinkler system which saves a lot of time and effort. I can get away with doing this now without negatively impacting on my plants because of the other measures I have in place.
As far as potatoes go, I just plant new ones earlier in the year, preferring to grow sweet potatoes instead during the summer months in my tunnels.