Tobacco Mildiyösü (Blueberry)

The pathogen overwinter in mycelium form on tobacco stalks left in the field after harvest. It is very rare for oospores to form in plant residues under the conditions of our country. In the spring, when the conidiospores and mycelium pieces reach the newly developing tobacco seedlings with the help of the winds, they carry out the infections.

The optimum temperature for the development of the disease is 18-24°C, and development below 2°C and above 27°C is almost nonexistent. If a conidiospore, which comes on the tobacco leaf in various ways, finds a small water droplet, it immediately germinates and releases grass tubes into the leaf tissue.

The fungus, which develops in the intercellular space and leaf parenchyma tissue for a while, then emerges from the stomata on the leaf surface and forms conidiospores again. The "incubation" or "incubation period" of the agent is 4-11 days, depending on the sensitivity of the plant and environmental conditions. The fungus forms new conidiospores at the end of each incubation period and spreads to the environment and makes epidemics.

Tobacco can be infected with this disease during the period from the emergence of the seedlings to the soil surface until the end of the harvest. The most favorable conditions for the disease are formed during the seedling period. Infected seedlings are more yellow than healthy ones. This jaundice extends from the site of infection to the periphery. The leaves of the sick seedlings take a convex appearance and the ends are slightly bent down. If you look at the undersides of the leaves, which are yellowish from the top, it is seen that they are covered with a grayish or off-white-light purple mold layer. If the weather conditions are suitable for the development of the disease, the spots in question in susceptible tobacco varieties cover all the leaves in a short time and such plants cannot develop and dry up.

If the pathogen infects the plant from the growth cone, it can also cause systemic infections in susceptible tobacco varieties. In such cases, the tissue in which the pathogen is located cannot develop, the symmetry of the leaf is disturbed, curls appear from place to place, and the plants remain stunted.

The symptoms in the field stage are very similar to those in the nursery. However, since the climatic conditions are not as suitable as the seedling stage and the seedling stage, the disease is mostly seen on the lower leaves. The multiplicity of rainy and cloudy days and the long-term persistence of the optimum temperature may cause the disease to spread. The first symptoms on the leaves are initially light green, later in the form of spots that turn yellow. These spots, which grow in a short time, become necrosis, dry and then puncture or tear.

The economic importance of the disease varies from year to year, depending on climatic conditions. The damage done during the seedling period reduces the cultivation area and reduces the yield during the epidemic years. In the field period, the dead tissues formed on the leaf surface by the disease agent greatly reduce the commercial value of the leaf. This is mostly due to changes in the chemical content of the leaf. Almost no product can be obtained from plants that have been systemically infected.

In our country, it is possible to encounter the damage of Tobacco Mildew in years and places where favorable conditions for the disease prevail.

The main host of the pathogen is wild and cultivated tobacco plants. Some strains can also infect plants of the Solanaceae family.

CHALLENGE
Cultural Measures

Disease resistant tobacco varieties should be grown.

-Seedlings should be established on light drained soils and in sunny places facing south, at a height of 15-20 cm from the soil surface.

-Seedlings should be established collectively in a certain area.

-Seeds should not be sown frequently. 1.5 g/m² of seed is sufficient for open pillows and 1 g/m² for closed pillows.

-Seedlings should be given enough water when necessary. Irrigation should be done early in the morning and should not be watered in the evening unless it is necessary.

- Fertilization should be done according to the results of soil analysis. One-way and excessive nitrogen fertilizer application should be avoided.

-Weed control should be done.

-No plant other than tobacco should be grown in the nursery.

- Seedlings with signs of disease should be removed and destroyed.

-After transplanting the seedlings to the field, all remaining seedlings should be destroyed.

- In closed pillows, the seedling covers should be opened on time and the seedlings should be ventilated.

-When planting tobacco seedlings in the field, the row and row spacing should be kept at normal distances, and care should be taken to ensure that the rows are in the direction of the prevailing winds.

-After planting, the field should be constantly monitored, the stained bottom leaves that show signs of disease on the plants should be stripped immediately, they should be removed from the field together with the plants with systemic infection and buried in a deep pit.

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Chemical Control (Tobacco Mildew - Blue Mold Medicines)

There is no need for spraying in the fields where resistant varieties are planted. Unless it is necessary, spraying should not be done during the field period.

Spraying time

In the nursery, after the seeds germinate and the seedlings cover the soil surface, spraying should be started after the planting work is finished in the field.

Tools and machines to be used

A back sprayer (mechanical, automatic, motorized) with a nozzle diameter of 1.5 mm should be used in nurseries. In collective nurseries and field spraying , it is more convenient to use a back atomizer with the nozzle setting no. 2 in terms of reducing the work intensity.

Spraying technique

- Spraying should be done both ways in the nursery and in the field, and both sides of the leaves on the plants should be sprayed.

-The most suitable time for spraying is morning hours and stagnant air. Spraying the seedlings should be done 1-1.5 hours after the morning watering, that is, after the water droplets on the leaves have dried.

-Tobacco seedlings susceptible to the disease should be sprayed every 4 days without interruption until they are transplanted into the field.

Spraying must be repeated in areas that receive more than 5 mm of precipitation in 24 hours. In climatic conditions where rainfall is abundant, proportional humidity is high and the temperature does not exceed 27°C, the spraying interval, which is every 4 days, is continued in the field. In cases where the relative humidity falls below 70% and the temperature increases, it is possible to open the intervals between spraying periods and take them 5-8 or even further.

* Ministry of Agriculture, Agricultural Protection Technical Instructions Volume 2