Fungicides, to be effective, must be properly applied. There are two important factors never to be neglected. They may be designated as timeliness and thoroughness.

Having determined on the proper kind of fungicide and the correct strength to be used in the case in hand, the question of the time of application comes up for consideration. Timeliness in making the application is the key to success in the control of diseases with fungicides. The stage of the development of the host must be the primary consideration; the tree, not the calendar, must be the guide. For example, the time to spray apple-trees to protect from scab is determined by the stage of development of the blossoms or fruit; first application, just before the blossoms open when the central blossom shows color and after the individual blossom-buds in the cluster have separated (Fig. 124). Second application, just after the petals fall (when two-thirds off) (Fig. 125), and so on. One must watch the trees closely and act promptly when they are just right for application. Seasons differ, varieties differ, and these facts must be taken into consideration. Next to the stage of the development of the host, as determining the time to spray, comes the weather. Spray just before rains, not after them. Remember that the fungus usually reaches the leaf or the fruit and produces infection during the rain, not before nor after. Get the fungicide on ahead of the rain and thus ahead of the fungus. Watch the weather maps and the developing blossoms. It will be more profitable in some cases to spray a little before the host is in just the right condition in order to get in ahead of a rain - period. Long, rainy, cloudy periods are the dangerous ones. Heavy showers followed by rapid clearing seldom afford conditions favorable to serious infection by orchard fungi.

The period for effective applications of fungicides, in practically all cases, is a brief one; at most a few days, more often only a day or two. This means that equipment, labor and materials necessary to cover the trees in a short time must be provided. The continuous running of one sprayer in a large orchard throughout the season is largely a loss of time and money. Fungicides to be effective must be applied at just the right time.

Thoroughness is second only to timeliness as a factor in determining the success of spraying or dusting operations. Since fungicides are applied to protect, every part of the susceptible surface must be covered. In spraying this cannot be done rapidly. Dusting can be done in much less time. Spraying will be much more thorough if done against, rather than with, the wind. Use a nozzle set at an angle of 60° on a ten-to fourteen-foot pole with a pressure of 175-200 pounds behind it. The spray should be fine and the nozzle should be moved along carefully and intelligently over every limb and branch. Where trees are fifteen feet or more in height, spraying should be done from a tower, and where the trees are very large, a man on the ground with a trailer will be necessary to cover the low - hanging limbs and lower inner branches. In spraying against the wind hold the nozzle at such a distance from the limb to be sprayed that the spray will come just where the wind breaks the force of the spray. Where spraying is done with the wind a second application after the wind changes is necessary. This is usually too late to be effective and requires double the time and material. Dusting is done with the wind, but here the light particles floating slowly through the branches settle and coat every part. Dusting is to be done at the same times that spraying should be done. However, since it can be done much more rapidly, the grower may often be able to make a timely application of dust which would not be possible with spray.

Fig. 125.   Apple blossoms in proper stage for the first application of a fungicide.

Fig. 125. - Apple blossoms in proper stage for the first application of a fungicide.

Fig. 126.   Apple blossoms in proper stage for the second application of a fungicide.

Fig. 126. - Apple blossoms in proper stage for the second application of a fungicide.

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