Disinfection of Vegetable Seeds

New Zealand Journal of Agriculture, Volume 87, Issue 3, 15 September 1953, Page 217

Disinfection of Vegetable Seeds

X/EGETABLE seeds of high germination capacity may fail to give " good stands of seedlings even when sown under ideal conditions of soil moisture, aeration, and temperature. Poor results under such conditions are usually due to the seeds or seedlings being attacked by ,harmful fungi, bacteria, insects, and nematodes (eelworm) which may be carried on the seed coats (seed-carried organisms) or by pathogenic organisms embedded in seed tissues (seed-borne organisms). In addition to seed-carried and seedborne organisms there* are a number of harmful organisms in nearly all soils which are responsible for rotting of seeds, damping off, seedling blights, or root rots. Special cases of failure of seeds to germinate owing to dormancy are not considered in this article by H. Jacks, Senior Plant Pathologist, Plant Diseases Division, Department of Scientific and ■ Industrial Research, Auckland, in which the most effective methods of disinfecting vegetable seeds are described. ■ "

FAILURE of seeds to germinate or of seedlings to emerge, commonly known as pre-emergence damping off, is due to: — ’ Soil-borne organisms (fungi (Fig. 1), bacteria, and insects) causing rotting of seeds or death of seedlings before emergence. Seed-carried organisms (fungi ,or bacteria) causing rotting of seeds in storage or after planting (Fig. 2). Seed-borne organisms (fungi, bacteria, or weevils) causing failure of seeds to germinate and diseases of plants grown from infected seed. Seedling stands are often thinned by attacks of soil fungi or bacteria on the roots and portions of the stems below or immediately above soil level. Wilting and death of seedlings after emergence are commonly known as post-emergence damping-off. Seed Treatments Seed treatments are designed to: 1. Prevent pre-emergence damping off through destruction of seed-carried organisms by therapeutant dust or slurry treatments. 2. Prevent post-emergence damping off, to some extent, by bringing about increased vigour of seedlings. 3. Destroy seed-borne organisms by hot water treatment or by chemical steeps. 4. Destroy virus or bacterial infection by special methods of seed extraction. ' 5. Destroy eelworm and weevil infestation by fumigation of seeds. Vegetable seed treatment is especially important in the control of damping off. Treatment protects the seeds and young seedlings from attack and' improves the stand, yield, and quality of plants and plant produce (Fig. 3). Although not highly effective for control of seed-borne diseases such as seedling blight of peas,' treatment reduces the incidence of such diseases. Seed treatments are usually effective against organisms attacking seeds in the early stages of seedling development; in some cases, however, they will protect seedlings, in the stage of aerial growth. Some materials are more effective against certain organisms than others.

For example, quinones (“Spergon” and “Phygon”) are more effective against bacteria than are other materials. Some seeds such as peas, french beans, and spinach, give better response to treatment than others (brassicas, radish, etc.). Materials and processes used in seed disinfection vary with the seeds to be treated and the organisms to be controlled; for example, beet seed is adversely affected by quinones, and the application of insecticides by the slurry method is more effective against wireworm than is the application of dusts. Treatments are.selected to give satisfactory control of harmful organisms without causing reduction of germination or damage to seedlings. Seed treatments recommended for use with vegetable seeds are described in Table 1. Soil conditions have an important effect on the susceptibility of seeds and seedlings to disease. With high temperatures and moderate soil moisture giving rapid germination and strong seedling growth, use of untreated seeds is often satisfactory. When cold and wet soil conditions delay germination of seeds and emergence of seedlings, thus prolonging the period during which pathogenic organisms can attack the seeds, seed treatment is essential. Under unfavourable conditions the strong, healthy plants produced from treated seeds are usually less subject to postemergence attack than less vigorous plants grown from untreated seeds. Seed disinfectants are inexpensive and easy to apply and should normally be used on all seeds, as they provide an economical method of protection against pre-emergence losses and in certain cases eliminate diseases attacking mature plants. The various methods used in seed disinfection are dusting, slurry treatment, hot water treatment, and special treatments. Dusting Seed dusts contain active ingredients (fungicides or insecticides), fillers (china clay, talc, etc.), which ensure even distribution of the active ingredients, and sticking agents, which ensure adhesion of dusts to seeds. The fineness of dusts may affect the amount adhering to seeds (often specified as load or cover) and thus their efficiency in seed protection. The finer the particles are the better the coverage of seeds with therapeutant and the easier the flow of seeds through drills. The nature of the chemicals and of the fillers used may affect the passage of seeds through drilling machines, where excessive "friction may cause clogging. Materials used must therefore be of a nature which will not affect the smooth flow of seeds through the drills. > Some dusts increase friction between seeds in drills, thus causing clogging with subsequent gaps in seed rows. To reduce friction it is advisable to add graphite to these dusts, as this material ensures smooth flowing of seeds through the drills. The normal amount of graphite applied to 1001 b. of seed is 1 to 3oz. Quantities of dust applied to seeds are measured in relation to weight and are defined as percentages of seed weight. Dosages vary with the seeds to which the dusts are applied, with the specific formulations of chemicals

in the dusts, with . the method of application, and with the disease to be controlled. The inclusion of sticking agents in formulations of dusts or wettable powders ensures effective coverage of seeds. Small seeds require higher dosages than large ones, as the smaller is the seed the greater is the surface area for a given weight. Where the quantities of dust required exceed those that will adhere naturally to seeds it is necessary to use sticking agents. This applies particularly to treatment of onion seed for smut control, for which higher dosages are required to protect seedlings from soil-borne infection. Stickers such as methyl cellulose, which is sold under various trade names like “Cellacol”, “Cellofas”, “Methocel”, and “Tylose”, are satisfactory and are safe to apply. It is not advisable to use wetting agents as stickers, as some depress germination. A home-made sticker is easily prepared by dissolving 3 grammes of resin in 10 millilitres of methylated spirit. Larger quantities may be prepared by dissolving 6oz. of resin in 1 pint of methylated spirit. The sticker is used at the rate of 0.5 to 5 per cent, of seed weight, for example, 1 to 51b. of sticker to 1001 b. of onion seed. The lowest amount (0.5 per cent.) was found satisfactory, in tests. In general, experiments with various seeds and the treatments listed in this article have shown that treated seeds can be stored as long as untreated seeds.

Inhalation of flying dust over a period may cause injury, the severity of which will depend on the toxicity of the disinfectant used, the amount of dust inhaled, and the period of exposure. Skin irritation may also be caused by some materials. Small-scale application of dusts is not risky. Largescale application, however, may involve operators in some toxicity hazards and the following . precautions are recommended. to F avoid injury. s 1. Wear a clean dry cloth or a dry filter mask over the nose and mouth (Fig. 4). Dust-mask filters should be changed regularly according to manufacturers’ directions. 2. Avoid accumulation of dust on the skin. Use protective ointment over exposed parts of the skin if sensitive to irritation.

3. Use gloves if handling large amounts of dusts. 4. Thoroughly wash hands, face, and exposed parts of the body before eating or smoking and at the end of operations. . ' 5. Clean up spilt material and do not allow dust to accumulate on equipment or on the floor. 6. Label treated seeds distinctly. 7. Do not use treated seeds for food or for feeding to stock. Methods of application are described in the following sections. Small-scale Application For treatment of seeds purchased in small packages and when the quantity of dust required is difficult to determine, a very small amount of dust, sufficient to cover jin. of the tip of a small pen-knife blade, is added to the packet, which should be shaken until the seeds and dust are well mixed (Fig. 5). A more satisfactory way of applying a seed dust to small quantities of seeds is to weigh the seeds and . the required quantity of disinfectant before placing both in a flask (Fig. 5) or a jar with a closely fitting lid. Seeds and dust are shaken for 5 minutes, thus ensuring adequate coverage. A small machine holding a number of jars is used at the Plant Diseases Division, Department of Scientific and Industrial Research, for treatment of small quantities of seeds. This apparatus is electrically driven and is geared to give 40 revolutions per minute. At this speed seeds and dust are thoroughly mixed and an even coating is given to individual seeds. The machine is illustrated in Fig. 6. Medium-scale Application For treatment of moderate quantities of larger seeds such as peas and beans a small hand-operated duster is satisfactory. This may .be made from a dust-tight drum provided with a closely fitting lid and mounted on trunnions (Fig. 7). :■ Thorough mixing of dust and seeds is essential, and is secured by mounting the container eccentrically on a shaft and providing interior flanges so that the seeds are thrown from side to side during rotation of the container. After the right amount of dust has been added the drum is turned for 5 minutes at 20 to 30 revolutions per minute. Care must be taken not to load ’the container beyond two-thirds of its total capacity. An electrically powered seed-dress-ing apparatus designed by the Plant Diseases Division gives ease of operation and optimum coverage of seeds. The capacity of the mixing drum allows treatment of 30 to 401 b. of seeds. Fig. 8 shows this machine. Large-scale Application Machines for large-scale application of dusts are so constructed that large quantities of seeds may be subjected to continuous agitation for several minutes (Fig. 9). '. V Measured quantities of seed dusts are automatically added to the flow of seeds to give a predetermined dosage. The machine stops automatically if seed delivery falls short of that for which it has been set and over-dress-ing is thus avoided. Other machines are of a gravity-, feed type and give treatment by passing seeds and dusts by gravity over a

system of cones and baffles, or of a type in which seeds and dusts are mixed by a rotating spiral conveyer. Adequate ventilation of premises is necessary ■ where large-scale seedtreating operations are in progress. Exhausters should be installed to draw off excess dust at the sacking end of some types of machines (Fig. 10). However, care must' be taken to ensure that exhaust fans do not withdraw more than the excess dust. Calibration of Large Machines Calibration of large machines is done by: — 1. Determining the exact amount of seeds delivered for a given time at a given setting of the seed feeder. 2. Determining the exact amount of dust delivered for a given time and at a setting of the dust feeder

corresponding to the desired dosage and the amount of seeds delivered. 3. Calibrating separately for each kind of seeds and disinfectant. 4. Recording accurately for each operation the amount of .seeds treated and the quantity, of disinfectant used. Materials and dosages of dusts to be used on different vegetable seeds are listed in Table 2. Beneficial effect of seed treatment,is illustrated in Fig. 11. The Slurry Method The slurry or short, wet treatment has been developed to give a more uniform coverage of seeds with disinfectants than is obtained with dust treatment. Although this method has shown certain advantages when compared with , dust treatment, it has not yet been introduced into New Zealand. It is suitable mainly for use by large seed firms for treatment of large, quantities of seeds, as more expensive apparatus is required than that used for application of dusts. The slurry method is the application of a disinfectant to seeds as a water suspension (slurry) instead of a dust. The slurry treater synchronises the flow of seeds and the slurry. High concentrations of wettable powders are used. These are formulated in a similar manner to that of dusts, but include instead of a lubricant a wetting agent and in addition a dispersing agent. The amount of water used for seed treatment is not sufficient to raise the moisture content of the seeds by more than 0.5 per cent. Seeds on leaving the mixer are coated with a uniform layer of fungicide or insecticide. Coverage of seeds is more permanent than in dust treatment. Small amounts of seeds can be treated in a conical flask or a jar. Larger quantities . are treated by special machines. Principles .of a slurry machine (Fig. 12) are as follows: Flowing into the hopper from an overhead bin, the seeds are

measured by a tilting seed pocket. When a certain quantity of seeds has flowed into the pocket, the pocket tilts and dumps its load into the treating chamber. A counterweight returns the pocket to its original position. The movements of the seed pocket are transmitted to an endless chain, equipped with small slurry buckets, by means of a shaft fixed to the back edge of the pocket. The slurry buckets are filled with sufficient chemical suspension to treat the seeds measured by the pocket. Seeds and slurry are supplied simultaneously into the mixing chamber. Distribution of the slurry over the surface of the seeds in the treating chamber is done by rapidly revolving agitator blades. The rate of flow of seeds may be adjusted, and any change in the rate of flow is automatically accompanied by a change in the flow of slurry. Seeds leaving the machine can be sacked directly if application of disinfectant .is correct. Calibration of machines may be done in a similar way to that given for dusting machines. Another ' method of applying liquid seed disinfectants is by directing highpressure spray against a descending stream of seeds. Treated seeds are then thoroughly agitated by a paddled shaft running in an inclined cylinder before they are discharged into sacks. Recommended Slurry Treatments Materials and dosages to be used on various vegetable seeds are given in Table 3. Valuable features of the slurry method of application are that it is rapid in operation, does not contaminate the atmosphere with dust, is economical in material, and ensures thorough coverage. Disadvantages of this method compared with dusting are that the equipment is more expensive, incorrect concentrations of disinfectants may cause seed injury, and it is not suitable for seeds of high moisture content, especially at temperatures below 50 degrees F. Hot Water Treatment The hot water process is used for control of diseases and pests carried within the tissues of various seeds.

Disease organisms are killed by temperatures lower than those tolerated by seeds. Hot water treatment includes several operations as follows: — (a) Pre-soaking: For certain species it is necessary first to soak the seeds in cold water to make them more permeable to heat. The seeds are placed in cheesecloth bags or wire baskets which are then immersed in a con-

(The first column under each chemical shows in pounds weight the quantity of disinfectant required for 1 gallon of water, and the second column shows in pounds weight the quantity of seed which can be treated by 1 gallon of disinfectant mixture.)

tainer of cold water. Duration of the pre-soak is shown in Table 4. Seeds are drained before being placed in the hot water container. (b) Steeping: For this process a container is fitted with some means of heating such as an electric element. A thermostat is necessary to hold the water temperature to within half a degree of that required. A goodquality thermometer which has been standardised is used to check temperatures. Constant agitation of the seed mass is necessary. Duration of immersion and temperature of the steep influence disease control and seed injury. Seeds are removed from the steep and drained before the next step. (c) Post-steeping: Seeds are immersed for a short time in cold water. (d) Drying: Seeds may be spread out to dry in a warm room. High temperature or direct sunlight should be avoided, as quick drying may affect germination. (e) Protection: When dry, seeds should be treated with a dust to protect them from recontamination with seed-carried organisms and from harmful soil fungi. The value of hot water treatment is that it eliminates seed-borne diseases which cannot be controlled by other means. This method, however, is difficult to apply and as it is liable to depress germination, especially when

Strain off the water through clean muslin and spread the seeds thinly on newspaper to dry. Wooden or glass containers should be used for this process, as the acid corrodes metal. Damp seeds should not be allowed to come in contact with metal.

old seeds are used or when temperature measurement is inaccurate, its use is limited mainly to treatment of nucleus lines of seeds. Hot water treatments effective in control of various diseases in some crops are given in Table 4. Special Treatments Some diseases such as tomato canker, tomato speck, tobacco mosaic, and tomato streak of tomatoes, and eelworm of onions may be controlled by the special treatments described here. Treatment of Tomato Seed Acid extraction: Add 1 fl. oz. of concentrated hydrochloric acid to the pulp from every 51b. of fruit. Thoroughly mix the pulp with the acid and allow the mixture to stand for 3 hours, stirring it at intervals. After treatment force water under pressure into the mixture and carefully pour off the water and pulp. Repeat this process until the seeds are clean.

Acid extraction eliminates the seedcarried diseases tomato canker, tomato speck, tomato streak, and tobacco mosaic. It _is advisable to dust acidextracted seeds with a recommended material for control of soil-borne 'damping-off. Acidulated mercuric chloride treatment: Tomato seeds which have not been treated by acid extraction and which could be infected with bacterial canker should be soaked for 5 minutes in acidulated mercuric chloride solution (1 gramme of mercuric chloride dissolved in 2.5 millilitres of concentrated hydrochloric acid added to 2000 millilitres of water). ' After treatment seed should be dipped in skimmed milk and dried. Dipping in skimmed milk neutralises any further action of the acid,, which could be detrimental to germination. After drying, seeds should be dusted with a recommended material.

Fumigation of Onion Seeds Onion seeds are sometimes infested with eelworm (Anguillulina dipsaci). Fumigation with methyl bromide is recommended for control of this pest. Treatments for small and large quantities of seeds are as follows: — Small quantities: For treatment of seeds m bottles fitted with ground-in glass corks or in other airtight containers 30 mg. of methyl bromide per litre are used. The time of exposure required to obtain complete control is 20 hours. Large, quantities: For treatment of seeds in vaults concentrations of fumigant should be increased to 60 fl. oz. per 1000 cub. ft. to cover leakages and possible absorption of the fumigant by the seeds or by other materials/in the vault. Germination of .onion seeds is not adversely affected at these concentrations. Use of Old Celery Seeds Seed transmission of leaf spot of celery (Septaria apii) can be avoided by planting seeds more than 2 years old. ;

I Book Review | jg .JjIIJIJIIELUjJJLrfJ

“Farm Animals”: John Hammond SINCE the first edition was published in . 1940 Hammond’s “Farm Animals” has enjoyed a well-deserved international popularity among students and progressive farmers. , The 1952 edition follows substantially, the same lines and style as those in the first volume. ; This new work merely brings up to date the very many subjects covered, and in addition includes a few new sections on animal production. Thus the section on genetics in relation to the practical problems of breeding farm animals covers considerably more ground than the previous treatment of the subject, presenting a useful summary of present knowledge. At the same time, it is noted that the author still retains his belief in the necessity for selection in an environment which will develop properly the character required. This view has, of course, been seriously challenged by New Zealand studies with identical twin cattle, from which it has been clearly demonstrated that selection for high milk production at least can. be effective in a poor environment. The book can be thoroughly recommended, however, to anyone seeking, in a compressed form, a knowledge of the wealth of factual data on farm animals which now exists. Dr. Hammond has- an extremely able tele-' graphic style which permits him to compress a vast array of facts into a very small space. He is also able to give us the benefit of his own interpretation of these facts and his general philosophy of animal production in an extremely clear manner. The book is well documented and will undoubtedly be a great success. ’ ’ \ Edward Arnold and Co., London. 18s. net.

—C. P. McM.

* To improve passage through drills it is advisable to add 2oz. of graphite to each 1001 b, of seeds treated with this material. e

controlled; soil decay

Chemical Trade name Percentage active Ingredients Description Colour Whether wettable : or not D.D.T. (dichloro diphenyl trichloroethane “D-spray 50” “Pespruf 50” 50 para,para isomer 50 para para isomer white grey yes yes Ferbam (ferric dimethyl dithiocarbamate) “Perham”* “Permspray” 98 70 black black no yes Thiram (tetramethyl thiuram disulphide) “Thiram”* "Tetram”* “Fernasan”* “Premasan”* “Thirodust”* “Thirospray”* 98 98 50 50 75 50 grey grey grey white grey grey no no no no no yes Gamma B.H.C. (lindane) 99 to 100 per cent, gamma isomer of B.H.C. “Lindane 25” “Nexa” 25. 16 white grey yes yes Dichloro naphthoquinone “Phygon” “Phygon XL” , 98 / 50 yellow yellow no yes Tetrachloro v para benzoquinone “Spergon” “Spergon W.” “Tetroc” 98 95 98 yellow yellow yellow no yes no ,

TABLE 1—DESCRIPTION OF MATERIALS RECOMMENDED FOR SEED TREATMENT

first Concentrations of Disinfectants and Amounts of Seeds — Crop Concentrations Amounts Treated first under chemical the shows “level teaspoons per pound”) “oz. per 1001b.” and the second column shows “level teaspoons per pound”) (50 per (50 p.p.i.). Ferbam “Fernasan” or “Premasan” “Lindane” (25 per cent.)“Phygon” “Spergon” or “Tetroc” Thiram or “Tetram” . “Thirodust” p.p.i.) Ferbam “Fernasan” or “Premasan” “Lindane” cent.) 25 per “Phygon” “Spergon” “Tetroc or Thiram or “Tetram” “Thirodust” (french) Beetroot Broccoli Brussels sprouts Cabbages Carrots . Cauliflowers . 1.6(1) 8.0(2) 2 4.0(2) 16.0(2) 16.0(2) 8.0(2) 8.0(2) 8.0(2) 8.0(2) 3 4 3 3 11 H U U 1.6(1) 4 2.0(2) 4.0(2) 4 2 4.0(2) 8.0(2) 8.0(2) 8.0(2) 8.0(2) 8.0(2) 1 1 1 1 1 2.0(2) 8.0(2) 8.0(2) 4.0(2) 4.0(2) 4.0(2) 4.0(2) 1 4 1 1 1 1 2.0(2) 8.0(2) 8.0(2) • 4.0(2) 4.0(2) 4.0(2) 4 0(2) 3 4 21 2i 11 11 11 11 2S 11 Celery . Cucumbers plants — — — — 16.0 (2) 8.0(2) 4.0(2) 3 U 3 4 — — 8.0(2) 8.0(2) 8.0(2) 1 1 1 8.0(2) 4.0(2) 2.0(2) 1 8.0(2) 4.0(2) 2 0(2) Kale .. Lettuces —- — 4.0(2) 1 4.0(2) 16.0(2) i 3 — — . 8.0(2) 8.0(2) 1 1 2.0(2) 8.0(2) 1 4 1 2.0(2) 8 0(2) 4 Onions . — — — — 800(2,3) 158 — — —• — — 400(2.3) 62 400(2.3) 142 Parsley . —. — — — 32.0(2) 6J — — 12.0(2) 11 16.0(2) 16.0(2) □ 2 Peas ... Pumpkins .. 1.6(1) 4 8.0(2) 1 4.0(2) 4.0(2) 1.6(1) 1 4 2.0(2) 1 4 4.0(2) 6.0(2) 1 3 2.0(2) 2.0(2) 1 2.0(2) 2 0(2) 3 1 Radishes Rhubarb . — - — — 4.0(2) 4 — — 8.0(2) 8.0(2) l 4 1 2.0(2) 4 2.0(2) i beet — — 16.0(2) 1 16.0(2) 3 — — 4.0(2) 1 8.0(2) 1 8.0(2) 03 Spinach . — — — 8.0(2) 11 — — 4.0(2) 1 8.0(2) 1 4.0(2) 4.0(2) if corn — — — — 3.0(2) 2 3.0(1) 1 2.0(2) 4 3.0(2) 1 2.0(2) 2.0(2) Tomatoes — ■ 16.0(2) 1 16.0(2) 3 — 6.0(2) 3 8.0(2) 1“ 8.0(2) I 4 8.0(2) 23 Turnips — 8.0(2) 1 8.0(2) 11 —• — 6.0(2) a 8.0(2) 1 6.0(2) a 6.0(2) 2 1.6(1) 1.6(1) 1 1 . / 8.0(2) ' 4.0(2) 8.0(2) 16.0(2) 16.0(2) 8.0(2) 2 ■' ■ 1 1 i 4.0(2) 16.0(2) 16.0(2) 8.0(2)' 8.0(2) 8.0(2) 8.0(2) 16.0(2) 8.0(2) 4.0(2) 4.0(2) 16.0(2) 800(2,3) 32.0(2) 4.0(2) 4.0,(2) 4.0(2) ' 16.0(2) 8.0(2) 3.0(2) 16.0(2) 8.0(2) 3 ' 4 3 3 1J 14 14 14 3 14 3 4 ■ s 3 158 6} 3 4 4 3 14 2 3 14 . 1.6(1) 1.6(1) 3.0(1) •i 1 ■ 2 2.0(2) 4.0(2) 2.0(2) 4.0(2) 4.0(2) 2.0(2) ’ 6.0(2) 6.0(2) . 1 4 1 2 . 4 1 4 1 4 ! 4.0(2) 8.0(2) 8.0(2) ' 8.0(2) 8.0(2) 8.0(2) 8.0(2) 8.0(2) 8.0(2) 8.0(2) 8.0(2) 12.0(2) 4.0(2) 6.0(2) 8.0(2) 8.0(2) 8.0(2) 3.0(2) 8.0(2) 8.0(2) 1 1 1 1 1 1 1 . 1 1 1 14 s 4 1 - 1 1 ’ i 1 1 - 2.0(2) 8.0(2) 8.0(2) 4.0(2) 4.0(2) . 4.0(2) 4.0(2) 8.0(2) 4.0(2) . 2.0(2) ' 2.0(2) • 8.0(2)-. 400(2,3) 16.0(2) 2.0(2) 2.0(2) 2.0(2) 8.0(2) 4.0(2) 2.0(2) 8.0(2) 6.0(2) 1 4 1 1 J ' 1 - . " ’ • 1 2 1? i 4 . 1 4 • 1 62 2 ■' I i 1 1 2 i ■ 1 a ' 4 ' 2.0(2) 8.0(2) 8.0(2) - 4.0(2) 4.0(2) 4.0(2) 4.0(2) 8.0(2) 4.0(2) 2.0(2) . 2.0(2) 8.0(2)400(2.3) 16.0(2) 2.0(2) 2.0(2) . 2.0(2) 8.0(2) 4.0(2) 2.0(2) 8.0(2) 6.0(2) ’• i . 22 23 14 14 14 14 22 14 3 4 3. 4 21 142 3 •I 2| U a 22 2 ■ :

TABLE 2-SEED DISIFECTION BY DUSING

Crop Concentrations of Disinfectants and Amounts of Seeds treated (for prevention of seed decay and damping-off) “Fermspray” “Phygon XL” XL” “Spergon Wet” “Spergon Wet” “Thirospray” “Thirospray” Beans (french) • \ •• 2.75 2.75 2300 2300 1.5 1.5 1500 1500 2.0 1 2.0 ’ 1800 1800 2.25 2.25 1900 1900 Beetroot — — 2.0 800 — — — — . 2.0 800 —— — — — Brussels i sprouts — — — — ... 4.0 800 1.5 1050 Cabbages — . — — 4.0 800 1.5 1050 Carrots ... — — — — — 4.0 4.0 800 800 1.5 1.5 1050 1050 Cauliflowers — ■ ■ — — — — 4.0 . 4.0 800 800 1.5 1.5 1050 1050 Cucumbers — — 1.5 2550 2.0 800 2.25 3000 Egg plants .. — — ' — —,— — 4.0 4.0 800 800 1.5 1.5 1050 1050 Kale .. • — — — _ J— -— — — 4.0 4.0 800 800 1.5 ' 1.5 1050 1050 Lettuces 3.0 .1550 1.5 1150 4.0 800 2.25 1150 Onions — — — —- ' — — — 1.5 1.5 1280 1280 Peas .. .. 3.0 2400 2.0 1800 2.0 1800 1.5 1250 Pumpkins — — 3.0 4800 2.0 800 1.5 1800 Silver beet .. . ■ ■■ — — 2.0 2.0 800 800 — — — — 3.25 3.25 2000 2000 Spinach . — — 2.0 ‘ 800 ■ — — — 2.25 2.25 1550 1550 Sweet corn .. — — 3.0 3600 3.0 2700 2.25 3050 Tomatoes ■ — — — 3.0 3.0 1200 1200 — — — — 2.25 2.25 1570 1570 Turnips . — — — — — — 2.25 1700 — ■ — 2.25 1700 ■ ’ j

TABLE 3—SEED DISINFECTION BY THE SLURRY METHOD

Crop Pre-soak Steep ■ Diseases controlled Time Temperature in degrees F. Time (minutes) Temperature in ■ degrees F. Cabbages .. . ' - 25 122 Dry rot Celery — 10 136 Leaf spot . 10 .136 Leaf spot Peas 18 hours approx. 55 20 ■ 118 Collar rot Swedes 15 mins. approx. 55 50 124 - Dry rot Turnips ;. — ■' . - . 30 122 Dry rot

TABLE 4— HOT WATER SEED TREATMENT