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What diseases are plaguing our beloved watermelons?

Watermelon bed Paying the main attention to the number and size of the ovary, gardeners sometimes forget to monitor the condition of the plants themselves, skipping the moment of infection of watermelons with such dangerous diseases for culture as true and downy mildew, all kinds of rot, as well as other diseases. The greatest damage to the crop is caused by fusarium and anthracnose..

Therefore, seeing a rotten watermelon on a melon, one should blame one’s own carelessness and pathogenic fungi, bacteria and viruses that cause most of the diseases of this plant..

Fusarium wilt of watermelons

Fusarium wilt of watermelons Penetrating through the root system and even the slightest tissue damage, the harmful fungus Fusarium settles and spreads through the plant through the vessels. A watermelon infected with this disease suffers and withers, because:

  • his vascular system is clogged;
  • the amount of toxins secreted by the fungus accumulates.

It is not surprising that the spread of watermelon disease, as in the photo, begins from the roots and the lower part of the lashes, because the fungus in the soil and on plant debris remaining on its surface can live for more than 4-5 years.

As a measure of control and prevention, after harvesting, it is imperative to collect and destroy the dried parts of the lashes, disinfect the soil, and it is even better to replace it in the greenhouse. The defeat of watermelons with this kind of disease is facilitated by:

  • general weakening of plants;
  • waterlogging of the soil;
  • failure to comply with the rules of crop rotation;
  • cooling the soil to 16-18 ° C.

The first warning signs of the presence of the disease can be seen already when growing seedlings. Young shoots with a fragile root system are quickly affected by a fungal infection present in the soil. If the crops are not processed in time and the infected sprouts are not rejected, the watermelon disease can also spread to the melon.

It is noticed that the disease is less common on well-drained light soils, with regular loosening of ridges and plants receiving potassium-phosphorus fertilizers, including foliar.

Anthracnose – a dangerous disease of watermelons

Anthractosis on watermelon leavesThis disease of watermelons, which occurs everywhere, except for the south of the country, affects all melons and gourds. Brown or yellowish spots of an indefinite shape appear on the green parts of the plants. As these spots expand, the leaves dry out and fall off, the stems weaken and break off easily. And the ovary affected by anthracnose is deformed, its development slows down or stops completely. As a result, stunted plants and rotten watermelons can be seen on the melons..

Elevated air temperature, lack of ventilation and light, as well as excessive soil moisture are the main factors contributing to the development of this watermelon disease. When it is possible to establish an irrigation regime and provide ventilation to the plantings, anthracnose stops spreading..

The source of the disease – a pathogenic fungus persists not only on dry parts of plants remaining on the ground, but also on seeds. During the growing season, the infection is transmitted by rain and wind, inaccurate watering, and also by insects.

Root rot of watermelons

Seedlings with root rotThe culprits for the spread of this group of diseases on watermelons are harmful fungi that infect first the root system, and then the entire plant. The disease can be recognized by the appearance of brown spots on the lower part of the stem and root, and root rot is most harmful to the seedlings. First, leaves turn yellow and wither on young plants, and then focal death of seedlings is observed.

Root rot also begins in adult plants from the lower leaves and sections of the stem. The dying off of the root system starts from small roots, gradually capturing the main roots that feed the plant.

Decay on the fetusThe development of root rot, like other similar diseases of watermelons, is facilitated by uneven or excessive watering, disharmonious feeding and low soil and air temperatures. If a favorable atmosphere for the fungus is created on the melon, pest spores develop and remain on dead tissues.

To reduce the risk of developing rot, it is important not only to carry out regular feeding, prevent overflow of beds and loosen the soil under the lashes, but also to remove all weed and dried plants.

With the early cultivation of melons and gourds, temperature fluctuations that are beneficial to the fungus should not be allowed. The crops are covered with a film or non-woven material, protecting from both temperature drop and excessive heat.

Bacterial spot

Bacterial spotThis watermelon disease is considered one of the most common not only on this plant, but also on other melons and gourds. The first signs of the disease are found already on the cotyledon leaves. But if here the spots are round or shapeless, then on real leaves the spots are limited by veins and already have a pronounced angular shape. The fabric inside the stain first turns brown, and then dries and crumbles.

When the fruit is damaged, the appearing brownish spots grow over time, have an oily blurry appearance. The tissues under such spots change their appearance up to the middle of the fruit, as a result, the watermelons are deformed and completely lose their quality. Even small manifestations of the disease on watermelons, as in the photo, lead to the unusability of the fruits, which after a short time rot.

Bacterial spot on berriesThe infection persists on plant debris, in the upper layers of the soil, as well as on inventory, structural parts of greenhouses and containers for storing watermelons.

If the melon is wet or dew falls out, droplets of liquid teeming with bacteria appear in places damaged by rot. As a result, the source of infection with insects, moisture and equipment is spread to neighboring plants and ridges. The penetration of the same bacterial flora occurs through the damaged surface of stems, leaves and ovary.

In just 5-7 days, the bacteria produce the next generation and are ready to infect new plants. Therefore, it is from bacterial rot that from 30 to 50% of plantings and crops can die..

Powdery mildew on melons

Powdery mildew of leavesWhitish or gray-pink bloom on the leaves of melons may indicate that the plant is infected with powdery mildew. This is the first phase of the watermelon disease. Then the heavily inseminated leaves are deformed, weaken and dry up, and at the site of the lesion by the fall, you can see black dots – the fruiting bodies of the fungus, ready to capture healthy plants in the spring..

Poured fruits are rarely affected by powdery mildew, but the damage of this watermelon disease is very great. Plants inseminated by the fungus develop poorly, form ovaries worse, and the fruits do not gain juiciness and proper sweetness.

During the summer, harmful microorganisms give several generations, remaining on the remains of plants for the winter..

The optimum temperature of infection is 20-25 ° C, but outside this range, the causative agent of this disease of watermelons is capable of infecting plantings, and powdery mildew is noted even in dry times, but in the presence of abundant morning dew.

Downy mildew on watermelons

Downy mildewDowny mildew is found on the leaves in the form of angular or rounded spots, and on the back of the leaf plate there are traces of gray or lilac bloom, consisting of mushroom spores.

Infected parts of the plant become brown, dried up and die, and the pathogens of the watermelon disease remaining on them, as in the photo, in a favorable soil environment survive from 2 to 3 years, remaining even after frosts and thaws.

During the growing season, spores of peronosporosis are carried with the inventory, especially often the disease is noted with high humidity and rather warm weather..

White rot

White rotThe disease caused by parasitic fungi occurs on many cultivated plants, the tissues of which, after being affected by the disease, initially become watery and then dry out. A whitish mycelium is shown in the places where the fungus is introduced. The causative agent of white rot remains in dry soil for at least two years, and in summer, mycelium particles are carried around the area by inventory or with the wind.

White rot on ripening fruitsThe air temperature lowered to 12-15 ° C, excessive humidity, as well as the use of cold water for irrigation becomes a favorable soil for the settlement of mushrooms. More often weakened plants suffer from white rot. It is possible to reduce the risk of infection and loss of yield by observing the rules of agricultural technology and crop rotation, removing all plant residues from under the plants and at the end of the growing season.

Found small traces of white rot on the whips can be carefully cleaned, treated with crushed coal or chalk.

Gray rot

A distinctive feature of this disease of watermelons is gray, accompanied by massive sporulation, plaque, which is preceded by a decay process when the tissue becomes watery.

The fungus-causative agent of watermelon disease persists in the soil for 2 years. The best conditions for the beginning of the mass development of gray rot are created when the air temperature drops 16-18 ° C.

Watermelon mosaic disease

On melons and gourds, the development of two types of mosaic disease is possible, which, in terms of external signs and the type of pathogen, seriously differ from each other..

Watermelon mosaic diseaseThe common cucumber mosaic, which affects all pumpkin plants, usually develops on adult plants and is expressed in the appearance of green and yellowish areas on the leaves and tissues. In this case, the surface of the sheet plates is often deformed, acquiring a swollen appearance in places.

However, the watermelon disease shown in the photo is manifested not only in this. Infected plants develop worse, leaves become smaller, internodes become shorter. The initial phase of the disease affects the tops of the shoots, the mosaic is especially pronounced at the time of fruiting, when the leaves completely die on the lower parts of the lashes, and then the lashes themselves weaken, the flowers fall off, the fruits acquire a mosaic color, are deformed and do not develop.

Mosaic rot is spread by aphidsThis type of mosaic disease of watermelons is more common in warm regions of the country, for example, in the Crimea, the Kuban and the Caucasus region. During the growing season, the mosaic virus can be spread by aphid colonies, in cold weather the pathogen remains on the seeds of melons, as well as on the roots of perennial plants, including weeds.

Green mosaic on the fruitIf plants are infected with the green mosaic virus, bulging bulges become noticeable on the leaf plates, but light green areas of mosaic color are not always formed. The disease in most cases settles in greenhouses. Green mosaic can spread when damaged parts of the plant come into contact with healthy ones. This happens when trimming lashes, pinching barnacles or picking fruits. The virus that causes the disease overwinters on seeds and plant debris, as well as in the topsoil.

To reduce the risk of developing a dangerous watermelon disease, you can:

  • using proven, disinfected seeds for sowing;
  • using disinfected soil mixtures for sowing and observing the rules of crop rotation;
  • planting only healthy seedlings;
  • observing agricultural techniques, including the rules for watering and protecting the plant from low temperatures;
  • destroying weeds, especially sow thistle;
  • timely removing diseased watermelon plants;
  • destroying aphid colonies on the site.

System of measures to combat diseases of watermelons

Compliance with cultivation techniques and timely prevention give a good result.Since the causative agents of watermelon diseases on particles of plant residues, weeds, implements, soil and seeds can remain viable for up to several years, the set of measures to combat diseases is necessarily based on prevention.

Plant residues from areas where watermelon diseases are noted must be burned or sent to compost, which takes at least two years to overheat. Moreover, such compost is regularly moistened and dug up. In the fall, the soil cleared of plants is dug onto the bayonet of a shovel with an overturning of the earthen coma.

Fruits even with minor damage and rotten watermelons should not be stored and in contact with healthy ones. Fruits intended for food and for obtaining seeds are regularly examined, rejecting watermelons with traces of spoilage.

Since the causative agents of dangerous diseases, for example, downy and true powdery mildew, bacteriosis and anthracnose, as well as viral mosaics, remain on watermelon seeds during the winter, it is important to take seeds only from healthy fruits for sowing. For the prevention of diseases of watermelons of fungal and bacterial origin, the seeds are disinfected.

For sowing watermelons, they choose lighted, easily ventilated areas, where melons, cucumbers and other representatives of pumpkin crops have not been grown for at least 3-4 years before. We must not forget about such prevention methods as:

  • regular gentle loosening of the soil;
  • plant feeding, providing the bushes with not only basic nutrients, but also microelements;
  • morning and evening watering that does not affect the leaves with water heated to 22–25 ° C;
  • maintaining a comfortable temperature regime of air and soil.

At the first signs of downy mildew and bacterial spotting, melons and gourds up to three times, after 1–1.5 weeks, are treated with 90% copper oxychloride. Colloidal sulfur, which is non-toxic to humans, animals and bees, will help from the manifestation of powdery mildew, which is used for irrigation at the rate of 50 grams per 10 liters of water. Watermelons are stopped to be processed a day before harvesting, which must be washed before eating..

In seedling boxes and greenhouses where melons are grown, it is advisable to regularly change the soil to a depth of 20 cm or disinfect it with special mixtures or copper sulfate..

Plant protection against fungal and bacterial diseases – video

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