The most unpleasant disease of onions - false mealy dew or peronosponoz. Almost all are surprised type of onions which have tubular leaves: napiform, Welsh onion, shnitt. This fungal disease can deliver great deal of trouble, up to yield loss and nullify all efforts of gardeners.
Symptoms of peronosporoz
Onions leaves lose emerald coloring, becoming more setly, with well noticeable yellowness at tops. The feather form changes, becomes flat and tape. Tops of leaves often accept arc-shaped orientation down. During wet weather the sick green leaves become covered by grayish or gray-violet dust-like raid fungal dispute which with wind and rain master new landings.
Leaves continue to turn yellow and dry up. Growth of plants stops. The fungal infection continues ""way"" to bulb. Next year on beds, new young leaves which will be ""got"" by the same fungus will give the landed onions or pilferers.
Infection sources
""House"" for peronosporoz are the struck long-term rhizomes of onions, bulbs, seeds, the postharvest remains of plants.
What should I do?
It is necessary to observe crop rotation. Onions to return landings to problem beds in 2-3 years.
To bring manure only under the previous culture.
Not to overfeed plants with nitric fertilizing. To use mineral fertilizers with the raised phosphorus doses. On poor lands to apply nitrogen fertilizers at the beginning of growth, in the second half of vegetation - phosphorus-potassium which increase resistance to diseases.
Before landing of onions (onion sets) it is useful to do thermal disinfecting. Onions should be warmed up at 40-45os within day. It is possible to ret onions before landing in solutions of copper vitriol or other fungicides.
First aid
At the first symptoms of disease it is necessary to process onions HOMOM (40 g on 10 l of water) or RIDOMILOM (25 g on 10 l of water). It is possible to repeat processing in one-two weeks.
At emergence 3-5 leaves of onions can be sprayed for prevention of landing of 3% with solution of margantsovokisly potassium of times in 7-14 days 2-3 times.
It is impossible to process onions on ""greens"" any medicines.