Treating the seeds of ornamentals is a common practice. Semesan has been widely used for this purpose.

The nonmercurial organics, such as Arasan and Spergon, also are satisfactory.

ORNAMENTALS grown from bulbs, corms, tubers, and roots also are benefited somewhat by the use of fungicides. Gladiolus corms, for example, are helped by a 15-minute dip in a solution of 1 pound of New Improved Ceresan in 50 gallons of water just before planting. The standard mercuric and mercurous chloride solutions also are used. Dipping the corms in slurries of Spergon, Fermate, or Dow 9 B after digging is beneficial.

Tulip bulbs have not responded very well to treatment. Some fungicides have lowered the yield of bulbs. Dipping bulbs in slurries of Spergon or Fermate has increased some yields. Narcissus bulbs may be dipped in a phenyl mercury acetate solution (1 pound to 800 gallons) for 5 minutes, after digging in spring and again before planting in fall, to control fusarium basal rot. Arasan SFX, Dow 9 B, and New Improved Ceresan also are beneficial.

HORMONES IN SEED TREATMENTS have been tried often. Results have varied. Of 30 investigators whose work was reviewed, 10 reported beneficial results from the use of growth-promoting substances on seeds. Twenty failed to obtain any benefits. Apparently the conditions under which hormones may or may not be beneficial in seed treatments are not fully understood.

Growth-promoting substances are used commercially to induce root formation in cuttings, prevent fruit drop in apple orchards, induce fruit formation without pollination in some plants, and to prevent sprouting in stored potato tubers. It seems reasonable that under proper conditions the materials may improve seed germination and early growth of the seedlings. Definite and reliable recommendations cannot be made until more extensive research has been carried out.

SYNERGISM AND ANTAGONISM between different fungicides, when mixed together, has been demonstrated often enough to restrain one from mixing fungicides with one another or with insecticides without knowing how they will affect each other and the seeds on which they are to be used.

A few examples of the effects of such mixing may be mentioned. The addition of New Improved Ceresan to DDT reduced both the fungicidal action of Ceresan and the insecticidal action of DDT. Magnesium oxide, added to copper carbonate or to Spergon, reduced the beneficial effect of those materials on emergence in wheat and on smut control in sorghum. Magnesium oxide also reduced the fungicidal efficiency of cuprous oxide and of Dow 9 B, but seemed to increase the fungicidal effectiveness of sulfur. Pyrophyllite containing 3 percent DDT when mixed with Dow 9 B reduced the control of sorghum kernel smut from 0.3 percent to 40 percent, with 6o percent infection in the check. Copper compounds in general are reduced in effectiveness when mixed with materials high in protein.

A good fungicide, prepared especially for seed treatment, usually is a well-balanced combination of active ingredients and suitable diluents, perhaps with the addition of wetting and dispensing agents, dyes, and other materials in proper proportion. The addition of other materials, such as insecticides or other fungicides, may cause chemical reactions and the formation of compounds that are ineffective as fungicides or injurious to the seed.

The labels on containers for fungicides used for dusting or spraying vegetation often mention the insecticides with which they are not to be used. Labels for seed-treatment fungicides, however, do not include such directions because, as a rule, those fungicides are not mixed with insecticides or other fungicides. That may change, however, with the growing need for combating insects that attack seeds after they have been planted. Experiments in New York showed that Arasan SFX mixed with chlordane, lindane, or aldrin and applied to lima beans prevented both seed rot caused by fungi and seed injury due to the seed-corn maggot. Mergamma, a treatment for cereal seed, contains phenyl mercury urea for the control of certain cereal diseases and benzene hexachloride for wireworm control. The number of these insecticidal-fungicidal seed-treatment combinations doubtless will increase, but their use in combination should follow careful chemical and biological experiments.

SEED INJURY following treatment was common when the treatments were mostly copper sulfate solutions, formaldehyde, or mercuric chloride, especially when planting was delayed after treatment.

When copper carbonate dust began to be used to treat wheat, it was found that delayed planting after treatment caused no injury to the seed but actually protected it against rodents and insects in storage. The more volatile organic mercury treatments, however, occasionally lowered the viability of seed after storage periods of more than a few days, especially when the moisture content of the seed was high. Several factors govern the degree of such injury: The moisture content of the seed; the volatility of the fungicide and the rate at which it is applied; the length of the storage period; the temperature, humidity, and aeration during storage; the kind of seed (seed of some genera, species, or varieties are more susceptible to chemical injury than are those of others); and the condition of the seed coat (cracked, chipped, or broken seed coats are conducive to seed injury).

IF SEED IS TO BE STORED for a while after treatment with a volatile fungicide, its moisture content should be relatively low-13 percent or less for cereals and a lighter rate of application used. Different portions of oats of 12 percent moisture content were treated with New Improved Ceresan at 1/2 and 1/8 ounce per bushel and either sown at once or stored for several weeks. The seed treated at the 1/2-ounce rate yielded better when sown the day after treatment. The seed that got the lighter application yielded better when souring was delayed for several weeks after treatment. Several experiments proved that sound seed of wheat, oats, and barley of good quality and proper moisture content, treated with one of the better organic mercury disinfectants at the recommended rate and properly stored fora year, was not injured in viability but yielded better than did untreated seed similarly stored. Occasionally in the more humid areas of the Southeast, treated seed is stored with a too-high moisture content and the poor viability is ascribed to the treatment. Subsequent tests often show that the viability of the untreated seed is equally poor.

PRETREATMENT OF SEED sold by seed dealers has been advocated for years. Some large seed houses pretreat seed of some field crops, such as cereals, flax, cotton, sugar beets, peas, corn, broomcorn, and some forage crops, either as a general practice or on a buyer's request.

Pretreatment of seeds by all dealers would mean cheaper but more general and more effective seed treatment; fewer outbreaks of preventable diseases; less waste of chemicals; less need of storing large stocks of chemicals in many places; more economical packaging, distribution, and use of seed-treatment chemicals; the use of the proper disinfectant at the proper rate for each type of seed; and many other advantages.

Some objections to general pretreatment of seed are valid enough. There is no general agreement as to what treatment is best for each kind of seed. Some buyers object to planting "poisoned" seed. Some persons might not realize that treated seed is sometimes poisonous and they might suffer injury. I think, though, that all the advantages of pretreating seed outweigh the objections.

Continued advances in seed treatment doubtless will bring new and better fungicides, better apparatus, and improved procedures into use. Fungicidal materials that promise to be more effective but less costly and less poisonous and disagreeable are sought. Slurry treaters that are more accurate and less troublesome are promised. A process that will fix the slurry fungicide to the seed and prevent its dusting off when the dried seed is handled will rid the slurry method of its chief shortcoming.

The possibility of systemic fungicides and chemotherapeutic disease prevention has been suggested and has been demonstrated in a few instances. This might eventually lead to the prevention of such Nation-wide calamities as epidemics of stem rust of cereals. Such fungicides would be applied to the soil and, when taken up by the plant, would render it resistant or fatal to the fungus attacking it. The fact that a tiny amount (3 parts per million) of selenium in soil is fatal to aphids and spider mites feeding on plants grown in the treated soil should encourage the search for fungicides equally effective against fungus infection but not poisonous to humans and animals. Such fungicides would be a tremendous advance in our war against plant diseases.

W. LEUKEL is a plant pathologist in the division of cereal crops and diseases at the Plant Industry Station, Beltsville, Md. He has been engaged in the study of the cause and control of cereal diseases since 1919 and is the author of more than 50 articles on the subject.

Conidia and conidiophores.