Anybody spraying against tomato blight?

[Primrose]

My ever-efficient computer diary has just reminded me that on this date last year I started spraying my tomatoes against blight. I did get a little but only lost a handful of tomatoes and wonder whether my action prevented a much greater loss.
There are no signs of it on my plants yet, but in view of the current weather (sunshine/ heavy showers/humidity ) I'm wondering whether I should start as a precaution, and if so, how regularly. All my plants are outdoors.

[Geoff]

I've had a few Smith Period warnings from Blightwatch but the map doesn't show many proven cases yet so I haven't sprayed so far.

http://www.potato.org.uk/department/kno ... 07&sy=2009

Blight.jpg (48.12 KiB) Viewed 6192 times

[glallotments]

We have had a Smith period warning too! I don't think they ever change that map.

No spraying though - just sitting tight!

[Chantal]

We've had two blight watch alerts of full Smith periods and I have now sprayed twice. It's very humid, has rained every day and I'm taking no chances.

[vivienz]

At yesterday's inspection, my outdoor toms have got the start of quite a bit of blight on them, not surprising with the recent weather down here.

I cut off the worst of it and sprayed with dithane yesterday evening. I'm hoping that it should stay under control as I've already been picking the first of the red alert and sungold, with plenty more to come.

Vivien

[Westi]

Hi Vivien

I'm registered BH23 with Blight Watch and have had no
alerts - and no sign of blight (yet). Here comes the
paranoia

Westi

[Westi]

Oops - Near miss today at BH23 so spoke too soon.
Time to get the spray ready!

Westi

[Primrose]

How regularly are people spraying? Once a week?
And how heavily? i.e. do all the leaves and fruit have to be dripping wet or will just a light misting suffice? I find the instructions are rather vague on these points.

[Chantal]

I've just had another blight warning for the CV22 area.

[Geoff]

Trouble is I don't think the rain will hold off long enough for spray to have any effect.

[Westi]

Full Smith period today at BH23 and I had to
work late so couldn't go to Lottie to spray so
determined tomorrow.

My spuds are Ok to just cut the hallums down
but my toms have a way to go so they definately
need attention.

If it rains will it wash the spores off the leaves and
if so do you spray the ground? How does blight
work - as non-technical as poss.

Westi

[FelixLeiter]

If it rains will it wash the spores off the leaves and
if so do you spray the ground? How does blight
work - as non-technical as poss.

Blight's a fungus. The spores need free moisture to germinate — mist or rain — and will penetrate the leaf, even a perfect one, through the pores and stomata. There is no purpose in spraying a crop once it is infected: there are no chemical controls which will cure a plant. You can only effectively prevent your crops from getting infected by spraying before there are any signs. There are commercial formulations which are effective after the event, but nothing that's available to the amateur.

[WestHamRon]

We sprayed 2 weeks ago. Since then we have had mild rain. Does rain wash off what we have sprayed ?

[Geoff]

I thought it would wash off with the heavy downpours we keep getting but I have packets of Bordeaux Mixture and Dithane and neither mention rain. Both say similar things.
BM for Potato Blight "Commence spraying before blight appears (usually late June to mid July depending on location) and repeat at two or three week intervals"; for Tomato Blight "Spraying should commence when the disease becomes active in late July to early August, repeat every three weeks"
Dithane for Potato Blight "Spray early July and repeat every 10-14 days while weather is warm and damp"; for Tomato Blight "Spray at first signs of disease and repeat at 10-14 day intervals"

Slightly odd that they are different when I thought it was the same disease, particularly it seems you can spray Tomatoes after you have seen some signs but Potatoes it must be before.

[FelixLeiter]

We sprayed 2 weeks ago. Since then we have had mild rain. Does rain wash off what we have sprayed ?

Well what have you sprayed with? Some sprays are topical, others are systemic. Bordeaux Mixture, for instance, is very soluble, so doesn't persist on the foliage for long. For definitive advice, read the manufacturer's instructions.