DEALING WITH DOWNY MILDEW
We never used to get any problems with downy mildew on onions. But for the past few years, just as they are beginning to bulk up nicely, the tips of the leaves start to go pale brown and when we look we can see the nasty grey spores developing. Is there anything we can do?
Downy mildew is definitely more of a problem than it used to be, and last year with its damp conditions, followed by this year's cold late spring, have made matters worse. The spores are airborne so rotating the crop (which you should be doing anyway) won't help much. F1 variety Santero, from Suttons, is allegedly mildew resistant. Bill grew these on William Road site in 2013 (very heavy clay) with excellent results.
Other things you can do are space the crop well, so the leaves don't touch, and watch any chives or welsh onion on your plot like a hawk - they may be harbouring the disease and infecting your onions.
Bordeaux mixture, a traditional fungicide, is not listed to control downy mildew in onions. However, experienced gardeners have found that, used as a 'foliar feed', it helps.
We never used to get any problems with downy mildew on onions. But for the past few years, just as they are beginning to bulk up nicely, the tips of the leaves start to go pale brown and when we look we can see the nasty grey spores developing. Is there anything we can do?
Downy mildew is definitely more of a problem than it used to be, and last year with its damp conditions, followed by this year's cold late spring, have made matters worse. The spores are airborne so rotating the crop (which you should be doing anyway) won't help much. F1 variety Santero, from Suttons, is allegedly mildew resistant. Bill grew these on William Road site in 2013 (very heavy clay) with excellent results.
Other things you can do are space the crop well, so the leaves don't touch, and watch any chives or welsh onion on your plot like a hawk - they may be harbouring the disease and infecting your onions.
Bordeaux mixture, a traditional fungicide, is not listed to control downy mildew in onions. However, experienced gardeners have found that, used as a 'foliar feed', it helps.
BASAL ROT is another fungus affecting onions. The bottom of the bulb goes white and fluffy at first. Later, black granular-looking spores develop. No chemical control is available and this sould-destroying disease can totaly wipe out your crop, so it makes sense to every measure possible to avoid it.
Basal rot is worst in wet soils or wet years. If your soil is clay, improve it with sand if you can. More useful, however, is to lime generously. It is helpful to grow onions in the same patch as cabbages, as they enjoy the same humus-rich soil and both need lime.
Some gardeners report that basal rot is more of a problem in onions grown from sets than in those grown from seed, so it is worth trying seed-grown plants if you have had difficulties with onions grown from sets.
Once those black fungal spores have had a chance to form, they stay in the ground for seven years, making rotation tricky. Try to grow onions in a different part of the rotation patch when they come round to the same patch again, lessening the chances of there being re-infection. Watch plants carefully and if a plant is looking sick, remove it immediately before the spores can form. Onions with basal rot grow poorly and the foliage will wilt or yellow prematurely.
Tip from Tony Fagg! - With a trowel, remove the soil from immediately under the roots of an infected onion and bin it (not compost it). Either clean the trowel very carefully or keep an old trowel for this purpose!
Basal rot is worst in wet soils or wet years. If your soil is clay, improve it with sand if you can. More useful, however, is to lime generously. It is helpful to grow onions in the same patch as cabbages, as they enjoy the same humus-rich soil and both need lime.
Some gardeners report that basal rot is more of a problem in onions grown from sets than in those grown from seed, so it is worth trying seed-grown plants if you have had difficulties with onions grown from sets.
Once those black fungal spores have had a chance to form, they stay in the ground for seven years, making rotation tricky. Try to grow onions in a different part of the rotation patch when they come round to the same patch again, lessening the chances of there being re-infection. Watch plants carefully and if a plant is looking sick, remove it immediately before the spores can form. Onions with basal rot grow poorly and the foliage will wilt or yellow prematurely.
Tip from Tony Fagg! - With a trowel, remove the soil from immediately under the roots of an infected onion and bin it (not compost it). Either clean the trowel very carefully or keep an old trowel for this purpose!
