MOST COMMON DISEASES AFFECTING THE CUCURBITÁCEAS

Hello friend of the farms, I am going to talk about the Cucurbitaceae family, which includes more than one hundred genera and about 825 species worldwide. For those who do not know Cucurbitaceae are easy to recognize. They are herbaceous vines or lianas with leaves usually rather covered by trichomes (hairs) coarse, without stipules, with palmate venation. In the armpit of the leaf there is usually a vegetative bud, a flower, displaced towards the side a branched tendril, or some organization more complex than that. The plants are either dioecious or monoecious, and the flowers have hypanthose, an often complex androceo formed by sigmoidly wavy monotonous anthers, and an inferior ovary with parietal placentation. The corolla is usually more or less yellow, sometimes red. The seeds are more or less flattened "

Typical species

Melon Cucumis melo L.
Watermelon Citrullus lanatus (Thunb).
Cucumber Cucumis sativus L.
Pumpkin Cucurbita L.

At present, several species, native or not, are cultivated in this country, among which are zucchini, chayote, and different kinds of melon, cucumber and watermelon, among others. Integrated pest management forms a key part of what would be good agricultural practices. Within the scheme, planning from sowing to harvesting includes appropriate management of pests and pathogens associated with the area in which it is grown. In our dynamic environment of increasingly demanding and distant markets, the fine-tuned handling is highlighted to achieve the best products.
To achieve these goals, to prevent the spread of pests and not leave residues of chemical treatments on the fruits. So by breaking the life cycle of pathogens with the applications of products that are more friendly to microbial life and the environment, producers are enjoying having better profits and healthier products.

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POLVORIENTE CENICILLA:

Description: P. xanthii and E. cichoracearum are the two main fungi that cause dusty ash. P. xanthii is the most aggressive pathogen, since it seems that the outbreaks of this fungus intensify in the warmer months. The causative fungus is an obligate parasite (the host needs to develop) and the mycelium develops on the surface of the tissues of the plant. Attacks directly through the epidermis.

Symptoms and damage to the crop: Thanks to the development of resistant varieties in cucumber and melon crops, the symptoms in these are usually less frequent. However, the reduced yield, incomplete or early maturation, bitter taste in the melon and a shelf life cut in the zucchini negative effects of the disease. The initial symptoms are noted by dim chlorotic spots and then dusty-looking colonies (conidia and conidiophores) on the underside of the leaves. The structures can cover the beam and the underside, extending to petioles and stems. Plants with damaged stems become chlorotic and squat. The fruits are damaged by sunburn due to lack of foliage. The pathogen can completely cover the foliage in a week, thus affecting the process of photosynthesis.

Handling: Apply the fungicides every 7-10 days starting immediately after detection. It is important to maintain weekly inspections after flowering, because at that stage it is when the plants are most vulnerable. To obtain proper control, fungicide applications need to reach the underside of the leaves and lower leaves in the plant because the fungus develops there. It is recommended to alternate applications with different modes of action to reduce the risk of possible resistance in the pathogen, beyond ensuring that the spray has the greatest coverage possible.

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ANTRACNOSIS:
Description: Anthracnose is caused by a fungus, Colletotrichum orbiculare. This fungus attacks the cucumber, the melon and also the tomato.

Symptoms and damage to the crop: The first symptoms are yellow spots or areas imbibed in water in the leaves or fruits, so that the rainy times followed by high humidity are the most propitious periods for propagation. Attacked areas enlarge rapidly, turn brown and an imperfect hole forms within the spot. The attacked fruits have circular lesions filled with brown water that turn black as the disease progresses. The disease can attack the fruits in the plants and also when they are stored. The fungus spends the winter in the waste and seeds of the plants attacked. It can endure 2 years without an adequate host. This fungus typically spreads in the seed, and the spores depend on the water to spread the infection.

Management: The best prevention is to use resistant varieties whenever possible. Plant certified seeds free of pathogens. Avoid working between plants when the foliage is still wet. Correspondingly, it is necessary to avoid moving the machinery or workers from one field to another when the leaves are wet. Control the cucurbits that germinate out of season. Spray regularly with the recommended fungicides in your state. Bury crop residues after harvest.

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CUCUMBER MOSAIC VIRUS (CMV)

Description: The virus hibernates in many perennial weeds, especially attractive to aphids / aphids when these plants sprout again. Although the virus was named for the first crop in which it was detected, it can infect a wide variety of crops, including many cucurbits.

Symptoms and damage to the crop: Early infection of zucchini and melons is especially common. Aphids are the main and most important way of transmitting the virus. The zucchini shows severe sunken signs along the central vein and defoliation from which the plant no longer recovers. Regardless of the crop, a major symptom is a considerable delay in the vegetative development of the plant. The fruit suffers discoloration, although this symptom is not unique to this virus. The early decay of melon guides is generally attributed to CMV infection and should not be confused with collapse or 'sudden withering', which is a disease related to plant stress.

Management: The cucumber mosaic virus can arise in the seed, restricted to some crops and weeds. Some resistant varieties of cucumber are commercially available and produce a high percentage of fruits lacking the mottled distinctive. The rest of the available commercial varieties are vulnerable to this virus, although the yellow zucchini is also a carrier of a 'precocious yellow gene,' which serves to mask the characteristic color common in cucurbitaceous viruses. In general, a diligent program of aphid control is key in prevention, particularly when it is considered that chemical control does not serve to prevent or cure an already infected plant. The main strategy to handle this virus is to start with resistant varieties.

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FUSARIUM (FUSARIUM OXYPSORUM SP.)

Description: The Fusarium genotype causes a variety of diseases in cucurbits. Some species such as Fusarium oxysporum f. sp. melonis cause vascular wilt in the melon. Others such as Fusarium solani f. sp. Cucurbitae cause crown rot in zucchini. Finally, some species of Fusarium are responsible for rotting the fruit in pre- and post-harvest.

Symptoms and damage to the crop: The plant can be affected at any stage of production. In mature plants, where it is more frequent, there is yellowing in old leaves and wilting of one or more guides. On certain occasions, a sudden collapse can occur without any sign of yellowing of the foliage. Linear necrotic lesions can be observed on only one side of stems close to the crown. The sudden collapse of Fusarium wilt should not be confused with the sudden melting of the melon.

Management: The pathogen is transmitted through soil and infected waste. Host infection begins at the root. The environmental and soil conditions are important for the development of the disease: it is more serious in the range of soil temperatures of 18 - 25 º C, and unfavorable on 30 º C. The following conditions favor the development of the disease: low humidity of the soil soil, high nitrogen content, especially in the form of NH4, and light, sandy and acid soils (pH 5.0 to 5.5).
Crop rotation is not effective at all because the spores survive for an indefinite time in the soil and the pathogen can survive on the roots of carrier plants without symptoms. Fumigation of soil with broad-spectrum biocides provides good control initially, but soil recolonization occurs rapidly. The most effective and practical way to control melon wilt by Fusarium is through the use of resistant varieties.

SOURCE:
https://www.conacyt.gob.mx/cibiogem/index.php/cucurbitaceas
https://www.hortalizas.com/cultivos/4-enfermedades-que-pueden
I hope that my article has been useful