HOW ULTRAVIOLET LIGHT CAN PROTECT YOUR CROPS FROM CERTAIN PATHOGENS

Hello friend of the farm in this opportunity I would like to comment the possibilities of the use of ultraviolet light to improve the quality of fruits and vegetables. I have always been passionate about the subject of light and how it affects human beings, insects, plants, and in particular the vegetables. Sometimes this factor is ignored, although it can cause significant changes in the behavior of plant tissues, before and after the harvest.
UV-C light can also induce resistance to various factors in tissues via "hormesis". In some studies on UV-C light treatments it has been shown that it can be used to control various diseases of fruits and vegetables caused by fungi and molds.

Ultraviolet light is a form of non-ionized radiation that does not penetrate beyond surfaces and is generally known as germicide (particularly at wavelengths near 250nm).

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BENEFITS OF USING ULTRAVIOLET LIGHT IN CROPS
UV-C can inactivate bacteria, fungi and viruses. Treatments in which the UV-C is combined with another disinfectant, work particularly well to lower the bacterial load of fruits and vegetables.
The sterilization of water filtered with UV-C is also effective; however, the effect is more limited on non-uniform surfaces, as in the case of fruit and vegetables.
UV-C light can extend the shelf life of fruits and vegetables through other effects. For example, it was observed that treatments of UV-C light reduced the incidence and severity of cold damage in bell pepper, which was evidenced at the metabolic level by reduction in the leakage of electrolytes from the cell walls, respiration rate and water content. phenols.
It has also observed beneficial effects of UV-C to reduce cold damage in mangoes.
Additionally, some studies suggest that UV-C can alter the nutritional composition of some fruits and vegetables, revealing their potential use in "functional foods" [they provide health benefits beyond basic nutrition]. Under a system patented by Spanish researchers, 10 times more resveratrol content - a compound associated with anticancer properties - can be obtained in grapes when exposed to UV-C light after harvesting. The authors estimate that these grapes produce resveratrol in an amount similar to that obtained with seven glasses of red wine.
Although plants respond to UV light, they are known to play an important role in the photo degradation of pesticides.
On the other hand, a problem of UV-C light is that, sometimes the doses at which the desired effect would be obtained would negatively affect the visual quality.

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CONTROL OF PATHOGENS BY UV IN VEGETABLES
Powdery ash by Sphaerotheca fuliginea occurs naturally on the leaf. When the conditions are good, the fungus parasitizes by consuming the carbohydrates in the leaf, which results in a reduction in production. A daily treatment with low UV dose to kill the mycelium is effective against this parasite.
Botrytis grows in the dead material of the plant but can affect the living tissue causing serious damage to the crop. Some consequences are the affectation of the fruit or of the same plant. In young plants it can cause death. The fight against this fungus consists in the application of a daily treatment with UV radiation.
Because Botrytis can attack again within 24 hours, it is necessary to apply the technique seven days a week.
In the cultivation of tomato the fungus of Botrytis usually penetrates in the plant through the wound that takes place after the defoliation. Therefore, it is recommended to adjust the lamps in such a way that they adequately illuminate the fresh wound in which the mycelium develops, before the fungus can penetrate inside the stem and protect against the effect of UV rays. Even if the fungus has penetrated the stem, it is advisable to continue illuminating this area. UV radiation slows the growth of Botrytis and delays its spread to other plants.
Cucumber mosaic virus (CMV) and Clavibacter in tomato and cucumber crops. These viruses have a low tolerance to UV radiation. By illuminating the crop daily, it is possible to prevent and delay the spread of viruses.
Micosfarela in cucumbers and Fusarium in peppers. The fight against these pathogens requires more effort than usual with the UV radiation technique.

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10 ADVANTAGES OF CONTROL OF PATHOGENS WITH UV RAYS
50% minimum savings on fumigation products
Better crop quality
No waste in the crop
Less stress in the crop
Without resistance
No re-entry time
Dry and clean technique
Biological pesticides are not damaged
Heat and CO2 savings
It is also effective against viruses and bacteria

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ADEQUATE DOSE AT THE TIMELY TIME
The dose needed to kill viruses and bacteria is relatively low compared to that needed to kill fungi. Therefore, with the controlled dose UV radiation technique it is possible to control these pathogens without damaging the culture. However, it is necessary to bear in mind that this radiation only controls fungi, bacteria and viruses that grow in the crop.
Once the disease has managed to penetrate the crop, ultraviolet radiation can no longer act. Therefore, it is extremely important that a daily treatment be performed. In spite of the daily application costs, these are not comparable with those caused by loss of production, reduction of income or cleaning. Other advantages of this technique is that it leaves no residue and can be applied unlimitedly without creating resistance.
UV light is a promising technology to improve certain quality variables in some horticultural products, as long as the cost is not prohibitive on a commercial scale. Although it can improve the quality and safety of whole and pre-cut fruits and vegetables, it is also clear that it has limitations.
The technique of crop protection by means of UV radiation at controlled doses (between 2 and 14 mJ / cm2) is an alternative for the control of diseases such as Cenicilla and Botrytis. The dose used in this technique is high enough to kill fungi, bacteria and viruses, but low enough to prevent damage to the crop.
Said dose depends on several factors such as power of the UV radiation application module and treatment speed. With these two variables, the dose can be calculated previously with great precision. As a confirmation, after completing the application, and whenever you wish, a measurement can be made with a certified instrument.

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NOVEDOSA APPLICATION OF UV AS FUNGICIDE
The use of UV radiation as a germicide for the sterilization of water, air or swimming pools is not new. UV radiation has been used as a substitute for chemical treatments in numerous industrial processes such as chlorination in the purification of water in cities, and preservation with formaldehyde in hospitals.
However, the use of UV as a germicide in agricultural operations is another story. UV germicidal lamps, such as those used in water disinfection, generate ozone and other byproducts that can be hazardous for workers and harmful to the crop. That is why the invention of Arne Aiking, the Technology of Protection of Crops with UV, is so important, by eliminating those barriers. Nowadays, the producer can apply Cleanlight in greenhouse crops without harming the workers or the crop.

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RUPTURE OF THE LIFE CYCLE OF THE PATHOGENIC HONGO
The fungal species have two stages in their life cycle - spores and mycelium. If we want to kill the spores, it is necessary to apply a high dose of UV light. This requires very powerful lamps and many seconds of exposure, which would not be practical in the greenhouse, in addition to the creation of potential problems for crops, workers and beneficial insects. If on the contrary we want to kill the young mycelium, it is enough with a tiny amount of UV light and one (1) second of time. In such doses, the treatment is safe for everyone. If we apply these low doses daily, the producer will be able to kill the mycelium every day, before it can generate spores and before it can penetrate the plant and damage it.

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HOW UV-C WORKS IN PRACTICE
We have already commented that water disinfection lamps are dangerous, so it was necessary to create special UV protection devices mentioned above, which provide a low dose of UV light.
In order to make this technology available to growers, Aiking turned to a partner, Harmen Van Kamp, who specializes in protecting crops such as tomatoes and roses, who developed the dose management team. The basic model consists simply of a manual operation cart with four units of UV-c lamps assembled to it. Workers operate the cart as they walk through the greenhouse at a normal rate to control the pathogenic fungus, just as they would to apply a chemical fungicide.
It has been estimated that workers can treat between 2 and 3 hectares in a normal work day.

SOURCE:
http://www.hortalizas.com/articulo/26146/sistemas-de-control-de-patogenos-por-radiacion-uv
https://www.hortalizas.com/poscosecha-y-mercados/inocuidad-certificacion/usa-radiacion-uv-para-proteger-tus-cultivos-de-ciertos-patogenos/

CONCLUSION
It is known that UV light has a direct effect on the pathogen, killing the mycelium, but there could be other beneficial effects. For example, in tomatoes, the application of UV results in a fortification of the surface of the fruit, although this effect alone would not explain the reduction of the pathogen in the fruits treated with UV.
Although more tests are required to evaluate additional beneficial effects and their efficacy in field treatments, the fungicidal effects of UV-c in greenhouse are presented as a viable alternative.

I hope that my article has useful service.