Powdery mildew onion, or scientifically peronosporosis, is quite common among diseases in a vegetable crop and is a threat future harvest.
- The biological basis of peronosporosis
- External signs of fungal disease
- Symptoms and contributing conditions
- Contributing conditions
- Agricultural machinery in the fight against infection
- Chemicals against peronosporosis
- Using chemistry
- Alternative methods
The biological basis of peronosporosis
Such a disease Garden crops, like peronosporosis, are of two types:
- powdery mildew itself, which appears on zucchini, pumpkin and many other melons grown in the beds,
- downy mildew onion, which most often damages the crops of cucumbers.
In both cases peronosporosis is fungal, although it is caused by various families of microorganisms. To combat it, use chemical preparations and folk remedies. The difference in powdery mildew on the onion and its double, downy mildew is that the outwardly initial appearance of the fungal disease manifests itself on the outer side of the leaf blade, and with downy mildew the inner side is affected, which subsequently goes up in the form of spots.
With peronosporosis, a plant can become ill not only during the growing season, but also during storage. It affects many types of onion crops: shallot, allspice, leek, batun, slime, chives.
The conidia of the infection are quite large in size, have an ovoid shape and gray color. At a temperature starting from 13 ° C and maintaining high humidity values, peronosporosis activates and spreads faster.
In conditions of drought and hot climate, fungal conidia die when exposed to sunlight, without causing damage to the onion culture. Microorganisms can spread through the air with wind gusts, with raindrops, and from a diseased plant to a healthy one through horticultural care.
The mushroom picker can remain viable throughout the winter, settling in the bulbs and root system.
External signs of a fungal disease
With powdery mildew, the onion is affected in the form of a rounded shape of spots with a pale green color, which appear on the foliage. Distinct white stains look like culinary flour, which can be noted in the photo. Without timely appropriate measures, the infectious disease begins to spread to the stem of the plant.
Over time, these white spots begin to acquire a brown hue, which indicates an overgrown neglected process, chemical preparations, for example, phytosporin, polycarbacin, arceride, will be required to combat them.
Infection it manifests itself differently in each garden culture: on a zucchini it leads to sharp wilting, on a berry bush bends branches and shoots, twisting foliage and covering with a touch of berries.
If the cause of the disease is an infected seed material, then two weeks later – on the 20th Shade after the bow rises, its feathers peronosporosis begins to appear as a large gray solid spots. If the plant is not treated and not saved, as a result of the development of the disease, the feather will wither and sag.
Symptoms and favorable conditions
To notice the symptoms of the presence of fungi in the planting material is quite problematic: at a glance, the plants affected in the previous sowing season do not lag behind in development, there are no external signs, however, during the period of foliage growth in late April – early May, affected areas become noticeable.
The diseased onion crop stops its growth and development and subsequently quently fade.
During moisture on the foliage, you can see the fungal spores which are formed externally in a raid gray hue. The mushroom picker is clearly visible in the morning, when the dew has not yet dried.The affected rough surface of the foliage often traps dust and soil dirt between the fungal particles, making the onion tops dirty. This appearance serves as a reason for the gardener to examine the plant for the presence of powdery mildew on the onion.
After some time, the spots become more noticeable and increase in size, and the foliage begins to dry prematurely. By the time the foliage dies, the fungal infection already penetrates the turnip, stopping the growth and storage disorders.
The infection causes a lot of damage to the testes, which causes the onion arrows turn yellow and break.
A month after the onion planting, green ones begin to appear or yellow spots with a gray spore coating.
For the development of fungal conidia there are a number of conditions conducive to their activity:
- they are capable of spread at night at a temperature of 4-25 ° C,
- for now humidity at least 95 percent,
- the presence of moisture residues on the plant at an ambient temperature of 1-28 ° C.
Fungi can maintain their viability up to 4- x days. Moreover, the incubation period for the development of fungal disease is on average from 10 days to 2 weeks. Stops the process of developing peronosporosis in dry, hot weather.
Agrotechnics in the fight against infection
Prevention of onion diseases with powdery mildew involves applying basic agrotechnical measures that allow you to grow a good crop, avoiding plant damage:
- the vegetable should be planted in places accessible to sunlight, on sandy and loamy soils,
- the onion planting bed should be provided with drainage and ventilated,
- for quick drying soil layer, weeds are destroyed and watering is not performed before night,
- planting onions occurs with the alternation of garden crops with a change in their place of cultivation,
- when choosing an onion variety for planting, those that have proved themselves to be resistant to disease are preferred
- planting the material warms up before storage,
- fertilizing the plant with nitrogen-containing mineral fertilizers only in the initial period immediately after planting, since nitrogen reduces the resistance of onions to fungal infections,
- avoid excessive watering, gradually turning into second half in growing season to regular loosening of the soil layer,
- the affected areas of onion culture are immediately removed,
- the onion is harvested in dry weather, followed by drying until the surface peel is completely dry.
The death of the mycelium inside the onion turnip can be achieved by heating the vegetable at 4 ° C for 8 hours.
Chemicals against peronosporosis
Chemical agents and folk remedies are often used as agents for powdery mildew onions, which can be used as a treatment or as a disease prevention.
Initial measures to control fungicide treatment are taken even before the detection of a fungal infection, when the onion plant gains p rest They do this with the help of Ridomil Gold in the proportion of 2.5-3 kg of the drug per 1 ha. When treating winter onions from powdery mildew, they use the same tool, starting to water after the appearance of 4-6 onion leaves.
You can achieve maximum efficiency and get rid of fungi if you make several treatments with Ridomil and spray the resulting peronosporosis up to 3 times.
With active growth of onion crops, when the main vegetative mass has already been gained, in the fight against powdery mildew onion, translaminar Quadrice treatment is used, which sprayes the onion at a rate of 1 liter per 1 ha with pro ezhutkom a week -. 10 days
If the primary signs of powdery mildew are found on the onion, the Bordeaux solution with a concentration of 1% helps to fight the plant with it, which can be used only earlier than a couple of weeks before harvesting the onion. It must also be remembered that the onion treated with Bordeaux liquid is not used on a green feather.
An alternative to this solution can be copper chloroxide in a proportion of 40 g per ten-liter bucket of water, arceride – 30 g per bucket. These preparations treat onions 20 days before harvest.
For the effectiveness of the aforementioned solutions, milk or soap is added to them based on no more than 1% of the total weight.
Processing is carried out at intervals of 1 , 5-2 weeks and cannot be more often than 2 times per garden season.
Among folk remedies, how to deal with powdery mildew on onions, gardeners emit fermented weeds, half a bucket of which are cut, filled to the brim with boiling water and infused for several days. They are filtered through cheesecloth and the onion is sprayed with the resulting liquid. Sour milk products in the form of yogurt or sour milk, diluted with cold running water at the rate of 1 to 10, are used to protect onions from powdery mildew.
By which saving a crop is a personal matter for every gardener, fortunately, the choice of funds is amazing. The main thing is not to let everything drift.