Hello friend of the farm in this opportunity I am going to talk about the asparagus is an export crop that is in constant growth for this reason the purpose of this article is to describe the symptoms and signs of the disease of the royal, its damages and control methods. Like all crops, it is affected by pests and diseases, which limits its production and quality. Among the foliar diseases, the Roya or Chauhixtle is one of the most common and represents a concern for producers, since when settling in the crop, yields fall considerably, by reducing the leaf area.
The asparagus adapts to semi-arid regions with acceptable development.
CHARACTERISTICS OF ROYA
This Roya presents all its structures in the same plant of the asparagus. It produces structures such as pycnias, aecias, uredias and telias in succession. It is called Macrocyclic Roya Autoica. When the Rust is severe, the foliage ages prematurely and the storage of carbohydrates in the crown is reduced, causing yield losses for the next cycle.
Young asparagus plants severely affected by rust. Note the premature aging of the foliage.
When asparagus plants have an acceptable nutrition, they can resist strong attacks of these pathogens.
On the right, plants strongly affected by rust. On the left, a plant of the same age, with good nutrition. In both cases the plants have no application of fungicides.
The reduction in crop yield is more severe when two successive cycles of infection occur. All commercial varieties are susceptible to this fungus.
SYMPTOMS OF THE DISEASE
Diseases caused by rusts are considered the most destructive in all crops. Asparagus rust is caused by the fungus Puccinia asparagi (specific to the crop, this species only attacks the asparagus).
Favorable conditions for rust. It occurs in the crop at any stage of it, when favorable conditions occur. These conditions are high humidity and presence of dew, with temperature range between 15 and 32 ° C. The fungus attacks all aerial parts of the crop.
SYMPTOMS IN CULTURE.
The symptoms appear as elongated spots (called pustules) reddish brown in stems, branches, leaves and shoots. Discoloration of the tissues occurs and is a consequence of spore attacks, which are produced in small pustules. At first, spots or pustules of reddish brown color (uredias) and then black appear.
The most observed phase in the field are uredias, where the spores are disseminated by the wind and under favorable conditions attack the crop. Each cycle is considered in an interval of 10 to 14 days. The black pustules (telias) are formed after the aecias and are those that go to winter, in crop residues and soil.
MEASURES OF CONTROL OF ROYA IN ASPARAGUS
The control measures are based on prevention and applications of fungicides. It is very important to follow the following control guidelines:
Destroy the volunteer plants at the time of harvest, in order to avoid inoculum.
It promotes the aeration of the crop with plantations of wide grooves and in the direction of the prevailing winds, which will allow a faster drying on the surface of the soil.
Maintain adequate levels of irrigation in order not to increase the humidity in the crop.
Consider the climatic conditions, mainly the presence of high humidity or dew, to decide applications of preventive and curative fungicides with registration for rusts.
In organic asparagus crops, the use of preventive sulfur and the use of products containing Bacillus species, is useful in the prevention of this disease.
Remove all foliage after cutting, because if there are structures of the fungus (uredospores) they can be disseminated by the wind. The foliage can be turned into compost to give it a usefulness. Avoid high planting densities in order to have more aeration in the crop. When carrying out a new planting it is important to orient the plants in the direction of the wind, in order to reduce the humidity. Optimize fertilization levels, since high doses of nitrogen induce the formation of more succulent and weak tissue, which is more susceptible to attack by the fungus. Calcium applications help to have stronger tissues.
Roya damage is greater in the early stages of crop development. The application of preventive fungicides should be carried out when favorable conditions arise. Mancozeb and Chlorothalonil are suitable. These inhibit the growth of the germinative tube and thus prevent the penetration of the fungus into the tissue.
Its application is done when there are symptoms of the pathogen (observation of pustules), without reaching a high percentage of the presence of the fungus. Among the most used fungicides are the inhibitors of Ergosterol synthesis. It is recommended to apply them together with preventives to avoid resistance.
One of the recommendations of importance in the application of fungicides is to consult the restrictions that the products may have for the export markets of the asparagus.
In management of Asparagus Rust, it is important to detect it opportunely and not allow the proliferation of this fungus, by means of prevention measures and / or use of appropriate fungicides for its control.
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