Downy mildew of cucurbitsis a disease that mainly affects cucumbers and pumpkins, both in greenhouses and in the ground. Althoughsymptoms of downy mildew of cucurbitsare initially only seen on the leaves, the disease can lead to the death of the entire plant within a few days. Learn the ways toecological control of downy mildew of cucurbitsin home and allotment gardens. We also suggest the bestspraying against powdery mildew on cucumbersand pumpkins.
Downy mildew of cucurbits
Fig. depositphotos.com
Downy mildew of cucurbits - symptoms
Downy mildew of cucurbitsis a fungal disease caused by the pathogen Pseudoperonospora cubensis. Of all pumpkin vegetables, it most often attacks cucumbers and pumpkins, although it can also be found on watermelons, squashes or courgettes. The biggest problem, however, is in the cultivation of cucumbers, both in greenhouses and in open fields.
In field cropsthe first symptoms of cucumber mildew are visible greenhouse crops may appear earlier). It can therefore be said that it is a very insidious disease that does not give symptoms for a long time and develops in hiding. However, when symptoms are noticed, under favorable conditions for the disease, it can completely destroy whole cucumber plants in just a few days.
The characteristic symptoms of downy mildew of cucurbitsare visible mainly on the leaves.Irregular spots appear on the upper side of the leaf, which are initially chlorotic and then turn brown. Usually, the area they cover is limited by the leaf veins, which is why these spots appear arranged in a mosaic. Over time, the spots grow in size and merge with each other until they finally cover the entire leaf surface. On the lower side of the leaves, a gray coating appears under the spots, which with time darkens and turns purple.
Downy mildew of cucurbits - symptoms on the upper side of the leaf
Fig. Christian Hummert, CC BY-SA 3.0, Wikimedia Commons
Downy mildew of cucurbits - symptoms on the lower side of the leaf
Fig. Rasbak, CC BY-SA 3.0, Wikimedia Commons
Conditions favoring the development of downy mildew on cucumbers
Understanding the conditions under whichdowny mildew of cucurbits infects plantsand thrives is very important to learn to properly prevent this disease.
First of all, it is worth knowing thatin the soil in our climate, the pathogen is not able to overwinterHowever, it can easily overwinter in heated greenhouses and compost heaps, in which, as a result of the decomposition of organic matter, there is usually increased temperature.
The development of downy mildew of cucurbits and rapid infection of plants is favored byhigh air humidity and cool nights with temperatures between 15-16 ° C and warm days with temperatures of 20-25 ° C. The spores of the Pseudoperonospora cubensis pathogen with gusts of wind can move quite long distances, intensively infecting other nearby crops.
Development of cucurbits' downy mildewis highly dependent on weather conditions, and favorable for the disease is a humid, rainy and windy summer.
Downy mildew of cucurbits - ecological control
Ecological protection against downy mildew of cucurbitsis worth starting at the stage of selecting cultivars resistant to this disease.This is especially important in the cultivation of cucumbers, which are easily affected by powdery mildew.
Polishfield cucumber varieties for organic cultivationare recommended, among others. cultivars Ares F1, Reja F1, Osiris F1, Zefir F1, Oedipus F1, Ibis F1, Ikar F1 are highly resistant to diseases of cucumbers, including downy mildew of cucurbits. However, you should avoid the quite popular variety of Śremski F1 cucumber, which is easily infected by downy mildew.
Since the pathogen does not hibernate in the ground, rotating vegetable beds and removing crop debris is not as important as it is for controlling other cucumber diseases. However, you have to be careful thatplant remains infected with downy mildew of cucurbitsdo not enter the composter, and you should thoroughly clean and disinfect greenhouses.
Sincethe development of downy mildew on cucumbers is favored by high humidity , spraying the plants during watering should be avoided, and it is best to install drip irrigation.It is also very important to avoid excessive plant density and to ensure airy conditions so that the plants dry quickly after rainfall. Greenhouses should be ventilated regularly.
Avoid planting cucumber cropsin valleys, near water bodies and forests, where there is high humidity and easy to maintain fog. If symptoms of the disease appear on the cultivated vegetables,remove leaves with visible mildew symptoms
so that the pathogen does not spread further. Remember not to throw these leaves into the composter. It is best to burn them or bury them deep.
Spraying for downy mildew of cucurbits
The ecological methods of combating downy mildew on cucumbers and pumpkins also include spraying with biopreparations prepared on the basis of weeds and herbs. Nettle manure can be used diluted 1:10, as well as horsetail decoction diluted 1: 4. These preparations are sprayed on the plants and the soil around them at intervals of 2-3 weeks.
Toprepare a stock of horsetail1 kg of fresh horsetail herb or 200 g of dried herb is poured over 10 liters of water and then set aside until the next day. After about 24 hours, boil the pickle and keep it on low heat for 30 minutes. After cooling down, strain the broth so as not to clog the sprayer nozzle.
Instead of making a decoction, you can also buy a ready-made horsetail preparation called Evasiol. A 50 ml package of this preparation is dissolved in 5 liters of water and the cucumbers are sprayed with it.
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What is very important,ecological spraying should be done preventively from the beginning of Juneand continued during the development of the disease, until September. Ecological spraying performed only after noticing the first symptoms of the disease may turn out to be insufficient.
If, despite organic spraying on cucumbers, pumpkins, watermelons, squash or courgettes, symptoms of downy mildew of cucurbits appear,spraying with copper or sulfur preparations For amateur crops on plots and in gardens, Miedzian 50 WP and Siarkol 800 SC will be a good choice.
Miedzian 50 WPis recommended for use in field cucumberas a preventive measure and after noticing the symptoms of downy mildew. We use it in the amount of 2.5 to 3 g per 0.7 liters of water, which is enough to spray 10 m² of cucumber beds. Spraying with copper should be repeated every 7-10 days, and during the growing season, a maximum of 3 such sprays can be performed.
Siarkol 800 SC is used in the amount of 15 ml of the preparation per 6 liters of water, which is enough to spray about 100 m2 of infected vegetables by powdery mildew of cucurbits.
Sulfurol 800 SC spraying on downy mildew of cucurbitsis repeated every 5-7 days, and a maximum of 6 such sprays can be performed during the growing season.If the symptoms of the disease are receding and there is no visible infection of new plants, you can return to organic spraying only or apply it every 10-14 days alternately with spraying with Siarkol 800 SC and Miedzian 50 WP.
