. Elementary principles of agriculture; a text book for the common schools . Fig. 92. Black rot of grape may be pre- vented by timely use of Bordeaux mixture vitriol) known as Bor- deaux mixture (given in the Appendix) is most often used. The plants are sprayed with a very dilute solution, so that a thin film of the poison covers the leaves, stems, buds, and fruit of the plant. Spores on the surface of thoroughly sprayed plants are killed, as Ukewise others that fall on the plants. It is often neces- sary to make several ap- pUcations, to replace the film of spray washed away by rains. Sulphur
. Elementary principles of agriculture; a text book for the common schools . Fig. 92. Black rot of grape may be pre- vented by timely use of Bordeaux mixture vitriol) known as Bor- deaux mixture (given in the Appendix) is most often used. The plants are sprayed with a very dilute solution, so that a thin film of the poison covers the leaves, stems, buds, and fruit of the plant. Spores on the surface of thoroughly sprayed plants are killed, as Ukewise others that fall on the plants. It is often neces- sary to make several ap- pUcations, to replace the film of spray washed away by rains. Sulphur, formaldehyde, and other substances, are used for special diseases. 220. General Methods in Using Sprays. Where efforts are made to pre- vent the attacks of fungi by sprays, it is important to know how and w^hen infection takes place. No general rules can be given. The time and manner of applying the fungicide must be suited to the conditions peculiar to the
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