Paying attention to the number and size of the ovary, gardeners sometimes forget thedit the condition of the plants themselves, passing the time of infection watermelons threatening diseases such as a true cultural and downy mildew, all kinds of rot and other diseases. Fusarium and anthracnose do the most damage to the crop.
Therefore, seeing rotten watermelon on a bahche, one should blame one’s own carelessness and pathogenic fungi, bacteria and viruses that cause most of the diseases of this plant.
Fusarium wilting of watermelons
A harmful fungus, Fusarium, penetrates through the root system and even the slightest damage to tissues, settles and spreads through the plant through vessels. The watermelon infected with this disease suffers and fades because:
- its vascular system is clogged;
- accumulates the amount of toxins secreted by the fungus.
Not surprisingly, the spread of watermelon disease, as in the photo, begins with the roots and lower parts of the whips, because the fungus in the soil and plant residues remaining on its surface can live for more than 4-5 years.
As a measure of control and prophylaxis after harvest, be sure to collect and destroy dried parts of the whips, disinfect the soil, and in the greenhouse it is even better to replace it. The disease of this genus contributes to the destruction of watermelons:
- general weakening of plants;
- does not comply with the rules of crop rotation;
- soil cooling to 16–18 ° C.
The first alarming signals about the presence of the disease can be seen already when growing seedlings. Young sprouts with an immature root system are quickly affected by the fungal infection present in the soil. If time does not carry out the processing of crops and do not discard infected sprouts, watermelon disease can fall on the melon.
It has been observed that the disease is less common on well-drained light soils, with regular loosening of the ridges and the receipt of potassium-phosphorus dressings, including foliar, by plants.
Anthracnose - a dangerous disease of watermelons
This disease of watermelons, occurring everywhere except in the south of the country, affects all melons and gourds. On the green parts of plants appear brown or yellowish spots of indefinite shape. As these spots expand, the leaves wither and fall, the stems weaken and break off easily. And the ovary stricken with anthracnose is deformed, its development slows down or stops completely. As a result, you can see stunted plants and rotten watermelons on bahche.
Increased 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 adjust the mode of irrigation and to provide airing for planting, anthracnose stops spreading.
The source of the disease - the pathogenic fungus is preserved not only on the dry parts of plants remaining on the ground, but also on the seeds. During the growing season, the infection is transmitted during rain and wind, sloppy watering, as well as insects.
Root rot of watermelons
The culprits in the spread of this group of diseases on watermelons are harmful fungi, affecting first the root system, and then the whole plant. It is possible to recognize the disease by the appearance of brown spots on the lower part of the stem and root, and root rot most harms the seedlings. First, young plants turn yellow and wither leaves, and then focal death of seedlings is observed.
Root rot begins in the lower leaves and stem sections in adult plants as well. The death of the root system starts from shallow roots, gradually capturing the main roots that nourish the plant.
The development of root rot, like other similar diseases of watermelons, contributes to uneven or excessive watering, disharmonious feeding and low temperature of the soil and air. If an atmosphere is created on bahche that is beneficial for the fungus, 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, to prevent overflow of the beds and to loosen the soil under the lash, but also to clean all weeds and dried plants.
In case of early cultivation of melon crops, temperature fluctuations that are beneficial for the fungus should not be allowed. Crops are covered with a film or non-woven material, protecting both from a decrease in temperature and from excessive heat.
This 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 already detected on the cotyledon leaves. But if the spots here are round or shapeless, then the spots on the leaves are limited to veins and already have a pronounced angular shape. The fabric inside the stain first turns brown and then dries and crumbles.
With the defeat of the fruit, the appearing brownish spots grow over time and have an oily, blurry appearance. Fabrics under such spots change their appearance up to the middle of the fruit; as a result, watermelons become deformed and completely lose their quality. Even small manifestations of the disease on watermelons, as in the photo, lead to the uselessness of the fruits, which after a short time rot.
The infection is stored on plant debris, in the upper layers of the soil, as well as on the inventory, structural parts of greenhouses and containers for storing watermelons.
If the bahche is wet or dew falls, on the ground damaged by rot, there are drops of liquid infested with bacteria. As a result, the source of infection with insects, moisture and inventory is spread to neighboring plants and ridges. The penetration of the bacterial flora occurs through the damaged surface of the stems, leaves and ovaries.
In just 5–7 days, bacteria give the next generation and are ready to infect new plants. Therefore, it is from bacterial decay that 30 to 50% of plantings and crops can die.
Powdery Mildew on Gourds
A whitish or pink-gray on the leaves of melons can indicate that the plant is infected with powdery mildew. This is the first phase of watermelon disease. Then the strongly inseminated leaves are deformed, weakened and dry up, and at the site of the lesion by the autumn you can see black dots - fruit bodies of the fungus, ready to seize healthy plants in spring.
Infused fruits of powdery mildew are rarely affected, but the damage to this watermelon disease is very high. Plants inseminated by the fungus do not develop well, form the ovary worse, and the fruits do not gain juiciness and proper sweetness.
During the summer, harmful microorganisms produce several generations, remaining for the winter on plant residues.
The optimum infection temperature is 20–25 ° C, but outside of this range, the causative agent of this disease of watermelons can affect planting, and powdery mildew is noted even in dry time, but with abundant morning dew.
Powdery Mildew on Watermelons
Powdery Mildew is found on the leaves in the form of angular or round spots, with traces of gray or lilac plaque consisting of mushroom spores on the reverse side of the leaf plate.
Infected parts of the plant become brown, dried out and die, and the watermelon pathogens remaining on them, as in the photo, survive from 2 to 3 years in a favorable soil environment, remaining even after frost and thaw.
During the growing season, the spores of peronosporosis are spread with the inventory, most often the disease occurs in high humidity and rather warm weather.
The disease caused by parasitic fungi occurs on many cultivated plants, the tissues of which, after being affected by the disease, become watery in the initial stage and then dry out. In places where the fungus is embedded, a whitish mycelium is shown. The causative agent of white rot is stored in dry soil for at least two years, and in summer, particles of mycelium are spread around the inventory or with the wind.
The temperature of the air, excessive humidity, as well as the use of cold water for irrigation, become favorable soil for settling the mushrooms. More often, weakened plants suffer from white rot. To reduce the risk of infection and yield loss can be, following the rules of agricultural engineering and crop rotation, removing all plant residues from under the plants and at the end of the growing season.
Small white traces of rot found on the lashes can be carefully cleaned, processed with crushed coal or chalk.
The distinguishing feature of this watermelon disease is gray, accompanied by massive sporulation, the plaque preceded by the process of decay when the tissue becomes watery.
The soil of the fungus, the causative agent of watermelon disease, lasts 2 years. The best conditions for the commencement of mass development of gray rot are created when the air temperature drops to 16–18 ° C.
Mosaic disease of watermelons
On the melons and gourds, two types of mosaic disease may develop, which in their appearance and type of pathogen are significantly different from each other.
Ordinary cucumber mosaic affecting all pumpkin plants usually develops on adult plants and is expressed in the appearance of green and yellowish patches on leaves and tissues. At the same time the surface of sheet plates is often deformed, acquiring in places a bloated look.
However, the watermelon disease presented in the photo is not only manifested in this. Infected plants develop worse, leaves become smaller, interstices become shorter. The initial phase of the disease affects the tops of the shoots, the mosaic is particularly pronounced at the time of fruiting, when the lower parts of the lashes completely die, and then the lashes themselves weaken, the flowers fall, the fruits become mosaic, deformed and do not develop.
This type of mosaic disease of watermelons is more common in warm areas of the country, for example, in the Crimea, in the Kuban and in the Caucasus region. During the growing season, the mosaic virus can be spread by colonies of aphids; in cold time, the pathogen is stored on the seeds of melons and crops, as well as on the roots of perennial plants, including weeds.
If plants are infected with a green mosaic virus, bulging bulges become visible on the leaf plates, but light green patches of mosaic color are not always formed. The disease in most cases settles in greenhouses. Green mosaic can spread when the damaged parts of the plant come into contact with healthy ones. This occurs when pruning lashes, nipping flowers or picking up fruit. The disease-causing virus overwinters on seeds and plant debris, as well as in the upper soil layer.
To reduce the risk of developing a dangerous disease of watermelons, you can:
- using proven, decontaminated seeds for sowing;
- using disinfected soil mixtures for sowing and following the rules of crop rotation;
- planting only healthy seedlings;
- following the agrotechnical practices, including the rules for watering and protecting the plant from low temperatures;
- destroying weeds, especially field sow thistles;
- timely removing diseased watermelon plants;
- destroying aphid colonies at the site.
The system of measures to combat the diseases of watermelons
Since pathogens of watermelon on particles of plant residues, weeds, inventory, 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 about two years to re-heat. At the same time such compost is regularly moistened and dug over. The soil cleared of plants in the autumn is dug up on a bayonet of a shovel with overturning of an earthen coma.
Fruits, even with minor injuries and rotten watermelons should not be stored and in contact with healthy ones. Fruits intended for food and for obtaining seeds are regularly inspected, discarding watermelons with traces of spoilage.
Since during winter the causative agents of dangerous diseases, such as false and powdery mildew, bacteriosis and anthracnose, as well as viral mosaic, remain on watermelon seeds, it is important for sowing to take seeds only from healthy fruits. To prevent diseases of watermelons of fungal and bacterial origin, seeds are disinfected.
For the sowing of watermelons, lighted, easily ventilated areas are selected, where previously melons, cucumbers and other representatives of pumpkin crops have not been grown for at least 3-4 years. We can not forget about such methods of prevention as:
- regular accurate loosening of the soil;
- plant nutrition, providing the bushes not only with essential nutrients, but also with microelements;
- leaves and morning watering, which does not affect the leaves, is heated to 22–25 ° C with water;
- maintaining a comfortable temperature regime of air and soil.
At the first signs of downy mildew and bacterial spotting, melons and gourds are treated for up to three times, in 1–1.5 weeks, with 90% copper chlorine oxide. Colloidal sulfur, which is used for irrigation at the rate of 50 grams per 10 liters of water, will help to show powdery mildew that is not toxic to humans, animals and bees. Watermelons stop processing the day before the harvest, which is necessarily washed before eating.
In the 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 the help of special mixtures or copper sulfate.