Methods Of Treating The Rust

All the cultivated varieties of asparagus are readily affected by the

rust, although it has been found that some varieties, notably Palmetto,

are less susceptible to its attacks than others. The most effectual

means of controlling the disease are spraying, burning of the brush,

cultivation, and irrigation.



Spraying.--Dr. Halsted, in his first experiments, used soda-bordeaux,

hydrate-bordeaux, and potash-bordeaux. The spraying began June 2d, and

ten sprayings were applied during the season. The applications were made

with a knapsack pump, and therefore were far more expensive than they

would have been if the sprayings were made with horse-power. With the

fungicide costing $5.00 per acre, and a machine that would spray two or

more rows at a time, it would be possible to reduce the cost to $10.00

per acre, or even less. In effectiveness the soda-bordeaux stood first.

Between the other fungicides there was but little difference. The best

results showed a reduction of rust of about one-quarter, which is not as

satisfactory a result as had been expected.



In the spraying work conducted by Professors G. E. Stone and R. E.

Smith, at the Massachusetts Experiment Station, the results were more

encouraging. The solutions used were potassium sulfide, saccharate of

lime, and bordeaux mixture. The spraying was done with a knapsack

sprayer, provided with a Vermorel nozzle, and after the first

application it became evident that the practice was of little importance

on account of the difficulty in making the solution stick to the plant.

For successful spraying of asparagus a finer nozzle is required than any

that is now in the market.



In some other experiments carried out on a small scale the asparagus

plants were practically covered with solutions, when they were put on

with an ordinary cylinder atomizer, and the lime solutions showed

excellent sticking qualities; but with the ordinary coarse nozzle the

solutions would run off of the glossy epidermal covering of the plant

very readily. Should the spraying of asparagus ever become a necessity,

then some apparatus which can be strapped to a horse's back should be

used. The narrow space between the rows forbids the use of the ordinary

mounted appliances, and if spraying is to be carried on upon a large

scale, it would be better to have the spraying mixture carried in some

manner on the horse's back. In this way it would be possible to carry

some thirty or forty gallons of mixture through the narrow rows.



Burning the affected tops.--There can be no doubt that by the burning

of the infested brush, after the cutting season, innumerable rust spores

are destroyed. But if this is done before the stalks are entirely dead

new ones will spring up at once, and in a few days will be as badly

affected as the first. The burning of the tops in the summer has,

moreover, a decidedly injurious effect upon the roots, seriously

weakening their vitality, and making the growth of the following year

still more susceptible to the infection.



In the autumn, however, after the stalks are dead and dry, this damage

does not prevail, and the spores upon old brush can be destroyed by

burning the asparagus stems either as they stand in the field or by

cutting and throwing the brush into piles. By the latter method many of

the smaller branches will be broken off and scattered upon the ground,

giving a suitable place for the spores to remain over the winter. For

the same reason it is an advantage to burn the brush in autumn instead

of the spring, and thus prevent the large loss of spores that would

obtain. In other words, burn the plants as soon as they become brown

and lifeless, for any delay means the breaking up of the brittle, rusty

plants, and a heavy sowing of the spores upon the ground. If the fire

could go over the whole field of standing brush, that would be the most

effective destruction. At best, with these precautions, many of the

spores will get scattered upon the soil, and it would be well to

sprinkle a thin coat of lime upon the ground and leave it there during

the winter. If this could be followed by a turning under of the surface

soil in the spring, it would bury the spores that might still be living,

so that they would be out of reach.



Cultivation and irrigation.--It has been observed that the injury to

asparagus plants, as a result of rust, has been confined to dry soils,

although there are places where beds in close proximity showed

remarkable differences as to infection; and that robust and vigorous

plants, even where cultivated on apparently dry soil, are capable of

resisting the summer or injurious stage of the rust.



In view of all the experiments so far made, and the experiences of

practical asparagus growers, Stone and Smith conclude that: "The best

means of controlling the rust is by thorough cultivation in order to

secure vigorous plants, and in seasons of extreme dryness plants growing

on very dry soil with little water-retaining properties should, if

possible, receive irrigation."



From a knowledge of the occurrences of the rust in Europe, and from

observations made in Massachusetts, they are led to believe that the

outbreak of the asparagus rust is of a sporadic nature, and is not

likely to cause much harm in the future, provided attention is given to

the production of vigorous plants.