Prevention Of Plant Disease

In the last two sections you have learned something of the nature of

those fungi and bacteria that cause disease in animals and plants. Now

let us see how we can use this knowledge to lessen the diseases of our

crops. Farmers lose through plant diseases much that could be saved by

proper precaution.

First, you must remember that every diseased fruit, twig, or leaf bears

millions of spores. These must be destroyed by burning. They must not be

allowed to lie about and spread the disease in the spring. See that

decayed fruit in the bin or on the trees is destroyed in the same

manner. Never throw decayed fruit into the garden or orchard, as it may

cause disease the following year.

Second, you can often kill spores on seeds before they are planted and

thus prevent the development of the fungus (see pp. 134-137).

Third, often the foliage of the plant can be sprayed with a poison that

will prevent the germination of the spores (see pp. 138-140).

Fourth, some varieties of plants resist disease much more stoutly than

others. We may often select the resistant form to great advantage (see

Fig. 119).

Fifth, after big limbs are pruned off, decay often sets in at the wound.

This decay may be prevented by coating the cut surface with paint, tar,

or some other substance that will not allow spores to enter the wound or

to germinate there.

Sixth, it frequently happens that the spore or fungus remains in the

soil. This is true in the cotton wilt, and the remedy is so to rotate

crops that the diseased land is not used again for this crop until the

spores or fungi have died.

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