Bulletin [No. 67 (Feb. 1926)]

GEORGIA ;TATE BOARD OF ENTOMOLOGY
ATLANTA, GEORGIA

BULLETIN 67

FEBRUARY 1926

SWEET POTATO SEED IMPROVEMENT, DISEASE CONTROL AND RULES PERTAINING TO THE PLANT
INDUSTRY.
I OF GEORG A
I
JAN 10. 19136
0. C. BOYD
Plant Pathologist
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HALIARD de La P ARELLE State Entomologist

GEORGIA STATE BOARD OF ENTOMOLOGY

ORGANIZATION

HON. J. J. BROWN, Chairman,

Atlanta

HON. R. C. BERCKMANS Macon

HON. T. G. HUDSON Anie:ricus

Staff

HALIARD de La P ARELLE, Atlanta

State Entomologist

W. W. CHASE, Cornelia

GEO. C. DECKER, Albany

Entomologist

Entomologist

E. F. GROSSMAN, Thomasville

0. C. BOYD, Thomasville

Entomologist

Plant Pathologist

M. S. YEOMANS, Atlanta

Chief Inspector

B. M. GADDIS, Valdosta Research

J. C. MANESS, Atlanta Field Agent

ROY ROGERS, Baxley Inspector
S. V. BROWN, Baxley Inspector
V. C. DURHAM, Savannah Inspector

C. H. GADDIS, Albany Research
W. H. LEONARD, Thomasville Supt. Station
W. L. NJ)~ESE, Atlanta Sec.-Treas.

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~WEE1.l::JOJ"ATO . SEED IMPROVEMENT, DISEASE CONTROL . AND RULES PERTAINING TO TH'E PLANT :INDUSTRY
By 0. C. Boyd, Patbol9giat.
Whether sweet potatoes are grown for home use, for shipping stock, or for plants, the grower should acquaint himself with the following information on seed improvement, disease control and on import~nt requirements connected with plant growing. It is the aim of the State Board of Entomology to aid the farmer and grower in improving his seed stock through the processes of selection and the control of fungous disea~es and insect pests; to prevent the entry into Georgia of disease we do not have and stamp out the dangerous diseases now present .and to bring before every potato grower and dealer the rules and regulations governing the introduction of sweet potatoes into the state and the production and sale of plants withjn the State.
LOSSES DUE TO DISEASES.
Georgia sweet potato growers lose annually unbelievable sums of money through storage rots, bed diseases and field diseases. The plant grower is required to comply with certain precautions for the prevention of disease in his crop. It is equally important for the farmer who grows pota,toes for home consumption or for marketing purposes to eliminate diseases from his stock and maintain only clean selected seed. It is only through such means that the maximum yields and profits can be realized.
During the past summer one South Georgia farmer stated that at least 25 percent of his potatoes rotted in storage during the preceding winter. Although he discarded at bedding time all potatoes which appeared to be affected with rot, he lost around one third of his draws due to a bed disease. On visiting his fields which had been planted to draws six weeks previously, we found only 25 percent of the plants alive, and every one of these was badly stunted due to black rot infection. . That grower was certain that the soil of at least three of his fields together with his stable manure, implements, and entire seed stock were heavily contaminated with the black rot organism. Although the party concerned stated his intention to start over with a clean supply of seed, it will require the strictest precautions possible to avoid infecting his new seed and clean fields on account of the presence of so much contaminated soil, manure, implements, etc., on his farm.
Stem rot or wilt, together with common storage rots is capable of producing a greater loss to the potato crop than the one disease cited above. Dry rot, which is a more destructive disease in Georgia than is generally known, like black rot brings about losses in storage, plant bed, and the field, but is most important as storage trouble. Every grower of sweet potatoes, no matter how large or small can
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with conscientious effort eliminate -disease from his seed stock ana premises, thereby enabling him to raise clean plants and a healthy crop of maximum yield.
HOW TO CONTROL SWEET POTATO DISEASES.
The potato growers should become familiar with the common methods that are known to be effective, practicable and profitable in the production of disease free potatoes and in improving otherwise the seed stock. These methods will be discussed in the same order that the grower will need to use them, beginning with the spring operations.
SELECTING POTATOES TO BED.
If the potatoes coming out of storage show a high percentage of rot, the seed should not be used for propagation. The entire lot should be destroyed by fire or disposed of in the manner discussed under the topic of sorting. If a fresh lot of potatoes is obtained for bedding, care should be taken to choose seed that appears free from storage rots, and that was dug from fields which were inspected and known to be free from wilt In case it is desired to import seed or draws from another state, it should be remembered that such plant parts must be _accompanied by a Georgia State Board of Entomology inspection certificate, signifying that they had passed an authorized inspection and found free from injurious diseases and insect pests, and that the potatoes had been disinfected prior to shipping. This state regulation is to protect our potato industry against the possible entry of the Sweet Potato Weevil, foot rot, and other dangerous pests common elsewhere but absent in Georgia. ,
SORTING BEFORE DISINFECTION.
Competent hands should be assigned to sorting over the potatoes carefully and discarding all roots that show rot lesions, whether soft or firm, deep cracks, bruises, cuts, etc. During the process o;f disinfection, the inner portion of the storage rot pits cannot be reached, and the diseases so represented will be carried to the plant bed, and in all probability to the field, if such roots are allowed to enter the beds.
The entire lot of culls should be destroyed by burning, or the roots appearing healthy might be used for food providing the peels are boiled for an hour. Likewise, the partially rotted potatoes might be fed to stock if first cooked for an hour. Should potatoes or peels that are infected with storage rot organism, or that are merely carrying the disease germs on their surface, be fed to stock, the germ will thrive and multiply in the manure for years. A splendid medium is thus afforded whereby the soil in fields and plant beds may become contaminated through the use of stable manure, a common means of maintaining black rot and stem rot in the potatoes and on the farm.
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DISINFECTING.
Sorting the potatoes as outlined above without subsequent disinfection is practically useless, as is also disinfection without previous culling Potatoes that show no rot whatever may be carrying on their surface the spores of black rot or other dangerous diseases, and are sure to contamiate the soil in the plarit bed and cause infection of the draws, unless properly disinfected. Disinfecting the roots before bedding kills all disease organisms on the outside of the potato. Culling and disinfecting are just as important for the farmer or the market stock grower. as for the plant grower who is required to employ those measures.
Precaution: Corrosive sublimate must be dissolved m hot water before it is added to the water in the dipping tank. Do not use metal containers. Do not discard or leave the solution where stock can drink it, for it is deadly poisonous when taken internally.
Procedure: Submerge the potatoes, preferably in baskets or hampers for ten minutes in a solution of corrosive sublimate (bichloride of mercury), one ounce to eight gallons of water. Remove and allow the container and potatoes to drain back into the solution for a few seconds. The potatoes may be bedded immediately without danger to draws, or may be allowed to dry and stored temporarily. It is importl;mt to know the exact amount of solution in the dipping barrel, vat, or tank at the outset of the proce-
dure. After dipping p.t the rate of ten bushels to each 30 gallons
the solution . should either be discarded and a fresh one made up, or be recharged with corrosive sublimate as follows: After disinfecting ten bushels in the original 30 gallons, add one-half ounce of the compound to each 30 gallons and add enough water to restore the original volume. Then dip another series of ten bushels per 30 gallons of solution, and again recharge. Recharge the solution no more than three times before discarding it. In other words disinfect not more than 40 bushels in each 30 gallons where the solution has been recharged three times. If the potatoes are unusually dirty, or if sacks are used as containers instead of crates or hampers, add three-fourths of an ounce of corrosive sublimate recharging instead of one half. Unless these precautions are strictly observed the potatoes will not be disinfected properly.
PREPARING THE BED.
Soil for the bed should be selected where sweet potatoes have not previously been bedded or grown, and the bed located where . drainage water will not wash from infected fields onto the beds. If old frames and sashes are to be used, they should be wet thoroughly with a corrosive sublimate solution 1 ounce to 8 gallons of
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water or other suitable disinfectantsas copper sulphate or formaldehyde. These precautions are necessary to avoid contaminating the beds with the organisms of black rot, stem rot and other diseases that are able to live for years in the field aiid in old beds. Stable manure should not be used as a "bed fertilizer or source of warmth unless it is known to be entirely 'free from disease germs. In any event it should be used sparingly and should not be allowed to come in contact with the potatoes or draws as it is highly conducive to the development of root and stem disease in the bed. Furthermore, manure used freely in plant beds is often responsible for an under sized root system on the draws. The proper use of commercial fertilizers is recommended instead.

BEDDING THE PO'l'ATOES.

During the' process of bedding, further culling out of undesir-

able roots should take place. After the potatoes are dipped, many

rotted spots will show up, due to the washing, that were overlooked

in the first sorting. Avoid crowding the potatoes, especially in

hot-beds.

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INSPECTING THE DRAW .BED. .

From the time the first plants come up until the pulling season is over, plants should be pulled and examined for black rot and stem rot infection. It is convenient usually to f~llow the pullers and examine the bunches that ate dropped in the same area from which the plants were pulled. If draws are found :mfected with black rot, showing as black scars on the lower end of the plant, or. with stem rot, showing as reddish-brown streaks when the base of the plant is split, the affected areas of the~ bed should be located and destroyed, and the soil disinfected by : soaking with corrosive sublimate or formaldehyde ( 1 ounce of :the former to 8 gallons water, or !pint formaldehyde to 25 gallons water). Plant growers are required to comply with these measures, including at least one thorough bed inspection; before a certificate is issued.

T~A~SPLANTING TO THE VINE BED.

No The practice of"se.tting the . field to draws sh~uld by all .means

be discou'taged.

matter how great the care exercised in culling,

disinfecting ami' bedding, it is possible for black rot and dry rot

to escape notice and .very probable that stem rot or wilt will be

entir,ely overlooked. By setting out just enough draws, however,

for a source of vine' cuttings and then usiiig only the latter for

setting.the crop or main field, it is possible to avoid almost complete-

ly the introduction of diseased plants in the fields. It is the. general

opm10n, furthermore, that potatoes gfown from vine cuttings are mqre sattsfactory for 'both plant 'production and marketing. .:...

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T-he vine bed should be inspected frequently, and all weak and diseased plants r<~gued out and destroyed. In cutting vines for the first setting, cut no closer to the central stem than 12 to 14 inches, otherwise runners might be obtained infected with stem rot. The only sure way of recognizing that disease is to split the stem of the plant or the base of the runners, and examine the woody strands. The latter, if diseased, will appear reddish-brown in color. As the plants in the vine bed grow older, it will be necessary to use only the ends of the runners for subsequent settings in order to avoid further probability of obtaining cutting_s infected with stem rot.
It is advisable to have both the draw bed and the vine bed at a distance from the main field and to avoid using the same implements for working the vine bed and the field. Draws and vine cuttings should be set in fields that have not grown potatoes for .at least four or five years. The organisms causing black rot, stem .rot and other diseases are able to live in the soil for that length of time.

INSPECTING AND ROGUING THE SEED-SOURCE FIELD.

The field from which the following years seed stock is to be

dug should be inspected frequently for the presence of diseased

hills. It is through these field inspections tliat stem rot can most

easily .be detected and eliminated.. . In some seasons the disease shows up early, in others shortly ~efore digging. Varieties differ

as to the time of summer the l;!ymptoms become most pronounced, and differ also in the degree of s~sceptibility. The grower should
look for stunted plants and fqr those that show a wilting of part

or all of the runners, or for hills that show perhaps only a slightly

premature defoliation. Stem rot can be detecte4 by splitting the

stem of the plant and the stem-end of the potatoes and noting

the color- of the fiber strands. Infected hills; including the run-

ners and the potatoes, whether the latter show the .discolored
stra~ds or not, should be remo. ved and destro. yed.

Black rot may also show up in the field, usually earlier in the s_easo.n as "misses'~ and. stunted plants. In this case the under-

ground parts of the plant exhibit the characteristic black, rotted

scars. The. potatoes may or may not have rot lesions. They should

be dug at any.. rate, and properly disposed of along with the remaind~r of.the plant, otherwise the disease ~ill appear in storage.
.. The summer or field inspection is one of the requirements in the rules and.' regulations govern~~g the productio!l and sale .of sweet

'potato plants, and is .as important for the farmer and growei' of



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commercial stock as it is for the plimt grower. It is one..-o.~. the

necessary . ;t;~ps to . take in ridding the seed and premises . of the

-~ost dangefous diseas~s ' of the sweet pot~to.

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SELECTING SEED FOR THE FOLLOWING YEAR.
The kind of seed saved, including type and its condition relative to the presence of fungous and insect pests, will determine largely the quality and yield that will be obtained in both the draw bed and the field. Potatoes for seed purposes should be selected for uniformity in size, shape and color and for complete freedom from diseases, undesirable types, etc. This .selection should take place at digging time, and the seed potatoes should be stored separate from the rest.
It is advis able for the grower of large acreages to maintain a seed lot. The latter consists of a small field well isolated from the remainder of the crop, set to vine cuttings from only healthy hills in the vine bed, and just large enough to supply bedding stock for the following year's crop. With a small field of this kind, the grower is able to inspect and rogue it frequently. Furthermore, he is able to check up on the quality and yield of individual hills. A corresponding system is used successfully by Irish potato growers who grow disease-free improved seed stock for both home use and for market. It is a practice that sweet potato growers might well adopt to great advantage.
DIGGING PRECAUTIONS
Sweet potatoes should be dug if posible on a clear day when the soil is relatively dry, and should be allowed to lie in the sunshine long enough to dry thoroughly before being hauled to storage. As freshly dug potatoes are highly susceptible to cuts, bruises, etc., they should be handled carefully and as few times as possible. It is the best practice to gather the potatoes in the same containers that will be used for storage, preferably crates.
STORAGE REGULATIONS AND SANITATION.
Storing potatoes in houses where humidity and temperature can be controlled is more satisfactory than storing in cellars, basements, and dirt banks. It is common observation that potatoes apparently healthy in all respects when entering cellars or banks for storage may rot severely, whereas roots from the same lots will remain sound in a well regulated storage house. This situation is due primarily to the difference in regulation of moisture and temperature, two important factors that influence not only the proper curing of the potatoes but also the activity of storage rot organisms.
During digging and for a period of ten days or two weeks afterwards, the storage house should be kept at a temperature of 80 to 85 degrees F., the most favorable temperature for curing the potatoes and drying the surplus moisture. The temperature should
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then be lowered gradually to about 50 to 55 degrees F., and maintained there for the remainder of the storage period. Ventilation should be so controlled that the maximum dryness will be maintained throughout.
Storage house sanitation is another factor absolutely necessary to consider properly in order to prevent loss through storage diseases. The houses should be cleaned thoroughly and all trash, debris, etc., burned. It should then be disinfected, together with previously used containers, by spraying the entire inside with one of the following disinfectants: formalin, 1 pint to 25 gallons water: copper sulphate, 12 ounces to 25 gallon water: corrosLve sublimate, 4 ounces to 25 gallons water, or the winter strength of lime sulphur spray used on trees. The interior should be allowed to dry thoroughly before the potatoes are stored. Where banks constitute the storage space, a location should be chosen where potatoes have not previously been stored or grown and only fresh straw or other similar material used. Banks should be supplied with proper ventilation. It is. highly important to exclude from storage all potatoes with cuts bruises, and rots and to store potatoes from different fields in separate banks or compartments. The latter precaution prevents the mixing of healthy and diseased lots.
OTHER LITERATURE ON SWET POTATO DISEASES.
The grower is referred to Farmers' Bulletin 1059, U. S. Department Agriculture, Bureau Plant Industry, Washington, lJ. . C., which treats the potato diseases separately, and includes illustrations together with the cause, recommends control measures, etc. for each. This bulletin can..be obtained by writing the above address or by writing the State Board of Entomology, Atlanta, Georgia.
RULES AND REGULATIONS GOVERNING THE MOVEMENTS OF SWEET POTATO ROOTS AND PLANTS INTO AND WITHIN THE STATE
1. All growers who intend to sell sweet potato plants the following year must apply to the State Board of Entomology, for inspections not later than July 31, in order to be included on the list for field or fall inspection.
2. It is illegal for anyone to ship or transport into Georgia sweet potato plants, draws, vines or cuttings unless each package is tagged with a Georgia State Board of Entomology inspection certificate. The latter signifies that before shipment the contents had been inspected by an authorized inspector and found ,free from dangerous diseases and insect pests and that the potatoes before
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bedding were disinfected in corrosive sublimate at the. :;trength of one ounce of corrosive subl~mate to 8 gallons of water. Sweet potato roots for propagating purposes. shipped from other states mu~t likewise be acco~panied by the inspection certificate, and must be disinfected before shipment. Sweet potato roots and plants from foot rot areas will not be allowed entry to the State. Violators of these rules will be subject to punishment by law.
3. In order to move or ship sweet potato plants, draws, vines, or cuttings within the State of Georgi.a, whether sell}ng, trading or giving away, the grower is required to have attached to each package or container a Sweet Potato Inspection Certificate issued by the Georgia State Board of Entomology, said certificate signifying that the grower's crop passed three inspections, one in the field, one in storage, and one in the bed; and signifying further through affidavit submitted that the potatoes were culled and disinfected before bedding in accordance with the prescribed regulations. Growers violating these regulations are subject to punishment by law, and those holding certificate tags will be required to forfeit same.
4. Freight and express officers are authorized to refuse potato plants without tags.
5. Dealers in sweet potato plants are required to purchase dealers' tags, and are authorized to purchase or receive otherwise only packages of plants that have attached to them the grower's certificate tag, .and are required to attach the dealer's tag to each package of plants disposed of. Dealers violating these regulations are subject to punishment by law, and their license will be revoked and their tags recalled.
6. Several southern states require sweet potato plant growers to secure permit tags and attach one of these tags to each package, in addition to the regular Georgia tag. The states requiring these additional tags are as follows: Mississippi, South Carolina, Alabama, and Tennessee. Alabama also requires a ten dollar ($10.00) license fee. Practically all states require.the filing of a duplicate inspection certificate issued by this Department. These certificates wiil be issued you by the inspector if you receive the three inspections. .
7. Bulletin 66 of the Georgia State Board of Entomology, issued September 1924, and entitled "Crop Pest and Nursery Laws of Georgia and Regulations of State Board of Entomology", will be sent free to anyone requesting same. This bulletin treats fully the rules and regulations pertaining to nursery stock and the sweet potato plant industry.
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