Kiran K. Shetty “Management of potato storage processesfor disease control”

(Kiran K. Shetty “POTATO STORAGE MANAGEMENT FOR DISEASE CONTROL”)
Potatoes can be stored successfully if the conditions meet the requirements and purposes for which it is laid. Disease problems in storage occur due to several factors, namely: the condition of the potatoes before harvesting, conditions during cleaning and storage, initial storage conditions, and sometimes external conditions
environment. Very often, adjustments are made after problems are identified. By understanding the conditions that lead to problems, they can be avoided or reduce by making the necessary adjustments.

CLEANING CONDITIONS

One of the key factors directly affecting the safety of the potato harvest is is the condition of the potatoes stored for storage. Ideally, potatoes are removed subject to the following conditions: formed peel, presence of cool air at night (required if there are refrigeration units in the storage), appropriate soil moisture to ensure soil-free harvesting and pulp temperature is about 15.5 `C. In some cases, soil conditions and temperatures pulps may be extreme and therefore may require some adjusting storage parameters at the initial stages. Here are some recommendations to adjust extreme conditions:

CLEANING IN VERY WARM WEATHER AND DRY SOIL:

1. Supply fans and humidifiers (if any) must operate at constant mode during the laying of potatoes and then, after the end of the laying, for another
   1-2 days.
2. Provide conditions under which the temperature of the air supplied to the embankment will be cooler than the tuber temperature by 2 °C. If the storage facility is equipped with fans for forced air supply from outside (with a capacity of more than 30 m3/hour per 1t) it is necessary to ensure the supply of outside air, for example at night, and reduce duration of ventilation with street air during the day, if the temperature air above the temperature of the pile; if potatoes are placed in the refrigerator compartment it is necessary to use refrigeration units to remove heat and reduce potato temperature; however, it is necessary to closely monitor temperature of the embankment, since a gradual decrease in temperature is preferable fast.
3. Once the pulp temperature reaches 10-12 °C (10 °C is preferable if available risk of developing pythium or wet rot) you can switch the program to therapeutic
   mode.
   
   

HARVESTING IN VERY WARM WEATHER WITH WET SOIL:

1. Supply fans (humidifiers, if any, turn off) must operate at continuously until the surface of the tubers becomes dry.
2. Separate harvesting of potatoes (placement in a windrow followed by selection) can be preferable to regular cleaning
3. Adjust the supply air temperature to 2°C below the bulk temperature.
4. As soon as the temperature of the embankment reaches 10-12 °C, you can switch the program to treatment regimen.

CLEANING IN COOL WEATHER (FROM 10 TO 15 °C) IN DRY SOIL CONDITIONS

1. The temperature of the tubers is already within the limits required for the treatment period. It is recommended to select the interval mode of fan operation in such a way that so that the temperature of the embankment remains stable, the supply will also be ensured oxygen required during the treatment period.
2. If possible, use outside air if its temperature is close to temperature of the tuber pulp.
3. If the outside air temperature during the day is cardinally higher than embankments – reduce or stop taking air from outside and use internal air to maintain a stable temperature of the embankment.
4. Potatoes stored under these conditions will require 2 to 3 weeks to treatment period at a temperature of 10 to 12 °C and at a relative humidity of 95%.

CLEANING IN COOL WEATHER (FROM 10 TO 15 °C) IN WET SOIL CONDITIONS

1. It can be recommended to use a separate method of harvesting potatoes (laying them in felling with subsequent selection) from damp areas. This will help dry the surface tubers.
2. The wet surface of tubers is a suitable environment for the development of diseases and prevents air exchange of the tuber through stomata. If the pulp temperature is close for treatment, it is necessary to ensure continuous operation of fans without the use of humidifiers. This will dry out the surface of the tubers. .
3. The supply air entering the embankment should be slightly cooler temperature of the tuber pulp (by 0.5 -1.0 °C).
4. As soon as the tubers are dried, it is necessary to ensure the conditions for the treatment period: temperature 10-12 °C with humidity 95% for a duration of 2 to 3 weeks.

CLEANING IN COLD WEATHER (TEMPERATURE FROM 4.5 TO 10 °C) AND IN DRY CONDITIONS SOILS.

1. Under these conditions, potato tubers are very susceptible to bruising on pulp – this requires more careful cleaning.
2. It is necessary to raise the temperature of the tubers to 10-12 °C. This can be done thanks to interval ventilation, which accumulates the heat generated during
   respiration of tubers.
3. Humidifiers must operate simultaneously with air supply fans.
4. If weather conditions do not change, it is necessary to continue the interval ventilation with humidification until the storage is full. If the weather conditions
   have improved and the air temperature has increased – you need to change the settings programs accordingly – it is recommended to pay special attention to
   batches of potatoes that are laid last.

CLEANING IN COLD WEATHER AND WET SOIL CONDITIONS (TEMPERATURE FROM 4.5 UP TO 10 °C)

1. It can be recommended to use a separate method of harvesting potatoes (laying them in felling followed by picking, provided there is no risk of frost.
2. The potato drying process must be started immediately after the tubers are planted in storage; continue until the desired result is achieved; make sure that
   the humidity inside the pile (storage) did not increase
3. If cold wet weather conditions slow down the drying process (achieve desired result) – you can gradually increase the temperature of the air supplied to
   collar, through the use of heaters.
4. When the drying process is complete, interval ventilation will ensure the required volume oxygen and, at the same time, accumulates heat generated during breathing tubers, for heating the embankment.
5. As soon as the temperature of the tubers reaches 10-12 °C, you can proceed to treatment period lasting 2-3 weeks at a relative humidity of 95%.

IDEAL INITIAL STORAGE CONDITIONS AND THEIR CONSEQUENCES:
Ideally, potatoes are harvested when the temperature of the tuber pulp is about 15°C, and for this condition, the initial storage temperature is set 2 ‘C lower than
pulp temperature during harvesting. Constant flow of air at a slow speed will help equalize the temperature in the embankment, reducing the likelihood of temperature changes in different parts of the embankment. Relative humidity must be maintained at 90-95%. When the storage is completely filled, the temperature in the embankment is required maintain at 10-12.5’C for two weeks to treat tubers. This includes the time to bring the pulp temperature to 10-13’C. At the end of the treatment period, the temperature of the embankment is reduced to storage conditions. Storage temperature determined by the end use of the potato. Although this practice is the norm, there may be exceptions. For example, if there is a suspicion of soft tissue infection rot or pythium, the best storage temperature is below 10 °C, which means that the actual set temperature when the storage is full is much lower. IN In some cases, the initial storage temperature is set at 9-10’C during the entire loading period, with fans running only at night during within 3-4 weeks. Then the temperature in the storage is gradually reduced at a rate approximately 0.5°C per week; or when the temperature difference between the supply air and the set value reaches 1° C, the set value is reduced by 0.5° C. This procedure continues until the potatoes are brought to storage temperature.

This practice is commonly used in fresh food packaging plants potatoes, and allows you to minimize the incidence of disease in stored potatoes silver scab. Lower treatment period conditions may not apply for potatoes intended for processing, since they synthesize sugar, which affects the color of the fry.

CLEANING IN WARM WEATHER.

If the weather is too warm during the day (pulp temperature 18°C or higher), the best Cleaning time is morning or late evening. It is important to note that if warm
weather persists, the main task should be to remove field heat first queue during storage. Potatoes should be cooled as they are stored using ventilation at a temperature of 10-12.5’C. This temperature along with humidity at a level of 90-95% will create ideal conditions for the healing period of potato type Russet Burbank

AT WHAT TEMPERATURES SHOULD THE TREATMENT PERIOD OF POTATOES BE CARRIED OUT?

The recommended temperature range for the treatment period is 10-12.5’C. The question is at what temperature to carry out treatment – 10 or 12.5 ‘C – may depend on the initial condition of tubers, end use of potatoes and consideration of possible diseases.

Russet Burbank type varieties intended for processing show the best results at 12.5C to avoid the risk of increasing sugar content. As it were a treatment temperature of 10 C is not unusual. Development and maturity of Russet Burbank determines the possible risk of sugar growth during treatment at a temperature of 10C. If potatoes is under stress or is overripe, there is a risk of sugar accumulation, which will affect the color of the fry. This issue is best decided on the basis of experience for specific region and specific production practice. If a threat is expected problems with rot occur, it is advisable to use temperature treatment period 8-10’C.

IS THERE A BENEFIT TO COOLING POTATOES QUICKLY?

It is generally believed that rapidly reducing the initial storage temperature to temperatures close to storage conditions can help prevent problems, associated with diseases during storage. However, this procedure is not without risks normal or overripe potatoes. If the potatoes are in good condition condition, this issue can be resolved taking into account the ultimate goal use of the crop. For fresh market potatoes, rapid cooling can have an advantage in that it prevents or delays the development of such diseases like silver scab. However, the disadvantage of rapid cooling is that potatoes located at the bottom of the mound can deform. This happens because when cold air enters the area warm potatoes, the air temperature rises, which reduces air pressure, which in in turn will cause the tuber to lose moisture. This loss of moisture will disrupt integrity of the internal cellular structure of potatoes. In addition, potatoes located at the bottom of the embankment, is subject to significant pressure due to weight.
This increases the likelihood of pressure spots and tuber shrinkage. The second disadvantage of rapid cooling is that if after cooling potatoes there will be a long period of warm weather, the influx of fresh air will have to limit for a long time, depriving the potatoes of oxygen, which will lead to accumulation of carbon dioxide and will cause the accumulation of sugars. Overripe potatoes will be especially sensitive to these conditions. Healing at low temperatures damage slows down in overripe potatoes.

COOLING TO Main Storage Temperature

The supply air temperature is reduced in steps of 0.5 ºС per day until it reaches basic storage conditions. This is first done by measuring the temperature recirculated air (although measuring the pulp temperature at the top embankment will be more accurate). If the air temperature is within 1º C of set temperature, it is necessary to lower the set temperature in increments specified higher. The best time to measure air temperature is early morning hours, because the embankment had gone through a long cooling period overnight. During Ventilation must always be provided for cooling. Once the conditions inside storages are stabilized, daily ventilation should be sufficient long-lasting to maintain a difference of 0.5º C between the lower and upper parts of the embankment. Increasingly, fans operate in shorter cycles (2 to 4 hours in one pass with a break of at least 2 hours). Shorter cycles are generally reduce extreme temperature differences between the top and bottom of the embankment. Should remember that if the fans stop for a long time, the embankment gets hotter, so it takes longer to cool down. This The recommendation is fairly new, so storage managers It is recommended to check the efficiency of the air system before making any changes.

MEASURES TO CONTROL SOME DISEASES DURING STORAGE

One of the most difficult situations faced by those responsible for storage is this is when they realize that the batch of potatoes they are storing is under serious threat
the threat of damage due to disease and any violations. From a management point of view, anticipating such problems is half the job of eliminating them. Given here
information concerns the anticipation of diseases during storage and the necessary steps for preventing or reducing the likelihood of a problem occurring.

PINK ROT:

Pink rot is a fungal disease caused by Phytopthora erythoseptica.
Characteristics of the disease:

1. The causative agent of the disease is transmitted through the soil.
2. When plants and tubers are infected in the field, plants may experience symptoms wilting and leaves may appear chlorotic.
3. Potato tubers become infected through eyes, lenticels and wounds and usually become infected in field.
4. Affected outer tissues of the tuber may have a brown color, especially around lenticels and ocelli.
5. Internally, the affected area spreads almost in a straight line throughout the tissue potatoes.
6. When cutting into affected tubers, the inner tissue becomes spongy and turns pink in 30 minutes.
7. Eventually, the affected tissue, when squeezed, may release a transparent odorless, watery liquid.

Causes:

1. Infection with pink rot of potatoes and tubers is favored by oversaturation fields with water.
2. Warm temperatures at the end of the growing season above 24’C are favorable development of the disease.
3. Soft rot bacteria can eventually infect potatoes affected by pink rot, and quickly destroy the tubers. In this case, an unpleasant odor often appears.

Control measures:

1. Avoid overwatering late in the growing season, especially if the temperature stays above 24’C.
2. Look for this disease in low-lying areas where water stagnates. If found Harvest these potatoes separately after harvesting the rest of the field. Put off cleaning
   of these potatoes and check for pink rot. If confirmed, no harvest the crops. If the harvest is harvested, sort it and dispose of it (sell it)
3. If the potatoes in the field are affected by outbreaks, and the choice is made in favor of harvesting along with other healthy potatoes, pay special attention to sorting and discarding affected potatoes. These potatoes should be placed last in storage closer to the doors so that it can be removed first or removed if and when it will start to deteriorate.
4. If the disease is discovered after the potatoes are in storage, ensure sufficient air flow through the embankment. During all the time required for drying potatoes, the temperature should be 8-10’C. If Only a small part of the mound is affected; healthy potatoes should be dried at temperature 10’C. Subsequently, rapid cooling to storage status. During this period, it is necessary to ensure a constant flow of air.

ПИТИУМ (ПИТИОЗНОЕ ИСТЕКАНИЕ):

Pythium is a fungal disease caused by Pythium ultimum.
Characteristics of the disease:

1. The causative agent of the disease is transmitted through the soil.
2. Infection usually occurs through natural openings on the surface potatoes.
3. Internal affected areas are clearly separated from healthy tissue by a dark border.
4. The decomposed tissue is spongy, and the affected areas may collapse internally, leaving the peel intact. This is often called shell rot.
5. The cut fabric turns from white to gray or dark brown.
6. The disease may appear within 2-3 weeks in storage. First sign problem areas appear in the form of wet spots on the surface of the embankment, arising due to the release of watery liquid from the affected tubers.

Causes:

1. High probability of disease occurrence in extremely humid conditions in field, followed by a short period of drought while the tubers ripen.
2. The disease is especially dangerous when the pulp temperature exceeds 21’C.
3. Pythium creates favorable conditions for bacterial soft rot infection during storage, which is distributed in storage, unlike pythium.

Control measures:

1. Collect tubers from suspicious areas in the field and place them in a plastic bag in warm conditions (at room temperature). Affected potatoes will quickly rot.
   If this is confirmed, avoid harvesting this batch of potatoes. If the party removed – sort and recycle.
2. Avoid harvesting potatoes in extremely warm conditions.
3. Avoid mechanical damage to potatoes during harvesting.
4. If a significant portion of the potato lot is affected, it is recommended to treatment period at a temperature of 7’C to 10’C for at least 3 weeks.
5. If the disease persists, you should quickly cool the potatoes to 4-7’C. Provide continuous forced air supply until the affected areas will dry out. Reducing the humidity during this process will promote drying.
6. Early release of the affected lot and placing it closer to the doors for simplify unloading.

DRY ROT:

Dry rot is a fungal disease caused by Fusarium sambucinum.
Characteristics of the disease

1. The pathogen can be transmitted both through seed material and through soil.
2. The pathogen enters the tubers through wounds and bruises received during harvesting harvest and loading and unloading operations.
3. Usually this disease can be detected under traces of mechanical damage on tubers. Infected areas of tubers inside are black and white, with crumbly tissue.
   The distribution inside the tuber is uneven, but between healthy and damaged tissues have clear partitions.
4. The outer surface of the affected areas may be sunken and wrinkled.
5. Sometimes you can see a white or pink fungal coating on the outside.
6. Secondary bacterial soft rot may eventually complete decomposition tuber.

Causes

1. Temperatures above 10°C usually favor the development of the fungus.
2. This disease usually occurs under dry growing conditions.
3. This disease can spread quickly if the treatment period is spent with disturbances during the first 2-3 weeks.
4. Typically, this disease is a problem if there is too much in the potato pile higher soil content.
5. Mechanical damage to potato tubers during harvesting and planting contributes to infection with this pathogen

Control measures

1. Minimize mechanical damage during cleaning and stowing.
2. Avoid harvesting potatoes at low temperatures of the tuber pulp, as Cold potatoes are very susceptible to bruising.
3. Ensure proper skin formation and ripeness of potatoes before cleaning.
4. Remove excess soil and clods during grading and mounding.
5. Post-harvest treatment of tubers is recommended.
6. Healing of damage is facilitated by a temperature of about 13’C at relative humidity 95%, the treatment period takes 2-3 weeks.
7. After completing the treatment period, gradually reduce the temperature by 0.5’C day before the main storage conditions are reached.

BACTERIAL SOFT ROT

Soft rot in storage is caused, among other things, by the bacterium Erwinia caratovora
Characteristics of the disease

1. Soft rot infection transmitted into the field through the stolon of an infected mother plants, is defined as blackleg. There may be some discoloration of blood vessels at the end of the stem and sometimes sunken areas of black tissue, spreading deep into the tuber pulp.
2. In storage, bacterial soft rot is an opportunistic organism and can cause serious problems when combined with other diseases.
3. Infection can penetrate into tubers through lentils and wounds, and externally infected areas may be brown to dark brown with watery skin textures.
4. Internal soft putrefactive tissues are moist, mushy or creamy with white or a grayish-brown coating. A black border is visible on the affected areas, separating them from healthy tissue.
5. In the early stages of soft rot, the rot is odorless, but appears over time unpleasant smell. When large areas of pulp are affected, storage may a characteristic odor reminiscent of ammonia appears. If the rot dries out, the affected areas become chalk white.
6. Decaying tissue of affected tubers can cause spread soft rot on neighboring tubers, blocking respiration in healthy tubers.
7. A potato mound severely affected by this disease may have a number of the following signs:
   a. may start to leak
   b. Thick, dark liquid may accumulate in the air passages.
   c. the temperature of the embankment may increase: this can usually be found in the upper parts of the affected area burt. Infrared heat detector can distinguish healthy areas from affected ones.
   d. Typically, a severely affected mound will emit a foul odor.

Causes:

1. Extremely wet conditions during crop growth and harvest.
2. Excessive number of weeds, which are host plants for this body.
3. Infected seeds increase the likelihood of infection of the offspring tubers.
4. Harvesting immature tubers.
5. Harvesting at pulp temperatures above 21’C.
6. Excessive air loss during ventilation in the storage along with non-working shutters.
7. Presence of free moisture due to condensation or improper distribution air in the collar.
8. Loading excess soil along with tubers into storage and inability to remove tops and lumps. All this leads to compaction of the embankment, impedes the movement of air and blocks the access of oxygen.
9. Diseases such as pythium and dry rot will contribute to the infection of soft rot.
10. Excessive mechanical damage and improper healing (treatment) contribute to infection with soft rot.

Control measures
There is little information to support the use of bactericides or disinfectants using humidifiers for direct control bacterial soft rot in storage. From a storage management perspective, you can consider the following:

1. Remains of soil from the previous season on the floor in the storage room, heavily contaminated bacterial soft rot must be removed and these areas must be
   thoroughly cleaned.
2. Use certified planting material, adequate watering and nutrition, provide weed, pest and disease control during cultivation for a healthy harvest
3. Monitor the formation of the skin and the maturity of the tubers before harvesting.
4. Cleaning with a minimum of mechanical damage.
5. Provide good grading to remove clods and soil during planting.
6. If some lots are suspected of being infected with soft rot, place them close to the doors for quick unloading if they start to spoil.
7. If a high percentage of the disease is noticed during storage loading or on early stage of storage, use low or no humidity with continuous air flow.
8. The correct curing period for healthy potatoes lasts for 2-3 weeks at a temperature of 10-13’C and humidity 95%.
9. If the disease is detected after the treatment period, then cooling to the conditions storage should be rapid, with a large volume of air supplied through the embankment.
10. Avoid condensation forming in and on the potato mound. Provide ventilation mode that can provide continuous but low-speed air supply for better equalization of temperature inside the pile. This prevents the formation of moisture inside the embankment and also ensures the supply of oxygen.
11. Use additional ventilation in heavily affected areas of the embankment