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Current management problems

Potato growing seasons, three factors have enhanced seed-borne disease problems. 1) Lack of information on effective fungicides for both post-harvest and pre-planting use against seed-borne disease causing pathogens (e.g. Phytophthora infestans and Fusarium sambucinum),2) An increase in the area of potatoes grown by fewer growers leading to management issues such as timing of pre-cutting of seed. 3)Climatic factors such as increased frequencies of rain events during the planting phase of the season

In combination, these factors can delay planting and increase the impact of seed-borne diseases during the early portion of the growing season and subsequently may affect yield and quality of the crop.

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I)During the pre-planting phase of potato production, seed tubers are warmed to about 54°F then cut into seed-pieces prior to planting.

V)Reduction in crop vigour results from expenditure of seed energy used to produce secondary or tertiary sprouts to compensate for damage to primary sprouts.

III)Damage at this stage results in delayed or non-emergence and is usually expressed as poor and uneven stands with weakened plants.

IV)Alternatively after planting, over 50% of sprouts developing on infected tubers may become diseased and may be killed outright before emergence.

II.Tubers infected with F. sambucinum are particularly susceptible to the development of seed piece decay during this phase and in cases of severe disease, seed pieces may not completely before planting.

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Management recommendation:

1. Plant only Certified Seed.

2. Varietal purity and disease standards regulated.

3. Historical aspects of seed, such as generation source, year,

grow-out tests and field observations (e.g. late blight) are

recorded.

4. Develop personal relationships between suppliers and

customers;

5. Assurance about growing and storage conditions e.g. fungicide

programs, storage treatments.

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Cultural practices:1. Arrange a mutually acceptable delivery time taking into account seasonal

temperatures at both locations. Unless thoroughly cleaned do not use a

storage facility where sprout inhibitors have been used.

2. Clean and disinfect seed storage facilities.

3. Ventilation system, plenums, ducts etc.

4. Brush down walls and floors.

5. Wash walls and floors (detergent and high pressure washer).

6. Re-cover surfaces with disinfectant (QA, Bleach, ClO2, and H2O2) for at

least 10 minutes.

7. Steam clean (in excess of 150°F).

8. Rinse and allow drying (hot or cold water). Cont….

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9. Do not store seed near potential sources of inoculums (e.g. cull

piles)

10. Keep seed lots as separate as possible.

11. On receipt, check certification documents.

12. After careful unloading seed should be stored at 40 to 42°F, 85 to

90% RH and be kept ventilated.

13. Prior to cutting seed the storage temperature should be slowly

raised to 50 to 55°F.

14. After cutting (and treating), seed should be piled no more than 1.8 m

high, stored at 50 to 55°F and ventilated to promote wound healing

(REI normally 24 hrs).

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Seed cutting Clean and disinfect seed cutters regularly.Use water impermeable seed cutters. Closed-cell sponge rollers are recommended.Keep the blades sharp and adjusted to deliver an average seed piece weight of about 2 ounces.Clean and disinfect cutting equipment, preferably each day and definitely between seed lots.Enforce sanitation practices for workers.Determination of Potential for Dry rot and Seed piece decaySeed lot should be visibly free of tubers with symptoms of Fusarium dry rot. Federal regulations allow 1% dry rot at shipping and by planting 2% level may develop (reasonable).Determine Fusarium inoculum on tubers visibly and also cut symptom-free tubers (about 50) in half, place in a large paper bag and shake them for about 2 minutes.Incubate about 50°F in high humidity and examine for symptoms of seed-piece decay after 10 to 14 days.

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Planting methods Potatoes should be ready in about 120 to 140 days. The potato flowering time usually indicates that they are swelling up.The time to harvest the early crops is determined largely by price prospects on the market, the weather, and to some extent the availability of labor.To promote a rapid and even emergence with plenty of stems and growth of the crop, as well as to facilitate and optimize mechanical operations in the fields.

Planting should meet the following conditions:

Minimum damage of pre sprouted seed during handling.Straight rows and equal spacing between the rows, fairly accurate spacing in the row.Uniform planting depth as shallow as possible, no contact between fertilizer and seed top recent damage to sprouts and rootsCovering of the potatoes immediately after planting to prevent damage to the seeds by heat and/or drying out of the soil around the seeds.

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Manual planting:Planting by hand is labour and time consuming. When planting in furrows, a toolbar with ridging bodies is generally used for opening the furrows.

This must be carried out immediately after planting.

Covering of the seed after planting can be done by hand or mechanically by using a toolbar with ridging bodies.

Fertilizer can be spread manually on to the bottom of the furrow and mixed with soil. It allows for an accurate spacing in the row and results in the least sprout damage.

Special attention should be paid to a correct and uniform depth control.

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Semi-automatic planters:

Semi-automatic planters achieve an acceptable capacity and can save

substantially on labour compared to planting by hand.

Suitable for planting seeds with weak sprouts.

This system is suitable for both seed stock propagation and the cultivation of

ware potatoes.

Machine is also fitted with furrow openers and covering discs.

One person can place between 80 and 120 seed potatoes in planting cups a

minute.

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It minimizes labour, as the only labour needed is the tractor driver.

These planters are capable of very good work at high speed.

The most common automatic planters are equipped with an automatic

feeding mechanism, consisting of a vertical revolving chain or belt with

two rows of cups.

With this system, the potatoes are arranged in a continuous line on the

planting belts to guarantee proper tuber spacing in the row.