The following notes on the effect of the copper sulfate solution on different plants are from observations and reports from various sources:

" Plants reported killed by copper sulfate solutions: wild mustard, wild radish, wild barley, penny-grass (if young), shepherd's purse, wild buckwheat, lamb's quarters, ragweed, sow-thistle, hemp-nettle, bindweed, dock, dodder.

" Plants reported severely injured; curly dock, black bindweed, dandelion, sow-thistle, and senecio.

" Plants reported as not injured: wild rose, poppies, pigweed, spurge, corn-flower, field-thistles, chamomile, couch-grass, bent-grass, and horsetails.

" Crops that may safely be sprayed:.all cereals, as wheat, rye, barley, and corn; the grasses; peas; sugar beets.

" Crops that are killed or severely injured by the copper sulfate solution: beans, potatoes, turnips, rape."

Charlock, known also as kale or wild mustard {Brassica Sinapistrum), is easily destroyed in oat-, wheat-, or other grain-fields by spraying with a solution of 1 pound of copper sulfate in 4 to 6 gallons of water (2 to 3 per cent solution). A force pump should be used, supplied with fine nozzles. The treatment is most effectively made when the grain is 3 to 6 inches tall, since at this stage the large charlock leaves spreading above the grain are easily covered by the spray. About one barrel of the solution (30 to 50 gallons) suffices to cover an acre and destroy the charlock, and this amount causes little or no damage to the grain. This same treatment is reported to be more or less effective against a variety of other common grain-field weeds. The wild turnip (Brassica campestris) and some allied cruciferous weeds are less easily killed because the spray does not adhere to their smooth leaves.

When to apply weed sprays (Ohio Station).

In practice, the time of applying sprays needs to be adjusted to the condition of the growing crop, and the relative development of the weeds to be killed. It seems probable that very early spraying will be less effective than spraying after the weeds have developed a fair supply of leaves. The first spraying should be made not later than the beginning of bloom. Repeated applications need to be made as often as a new supply of leaves is developed, provided the condition of the host crop permits this. In grain-fields, the best results will be obtained on practically all weeds, when only a single spraying is to be made, to apply the spray just as the crop is ready to occupy the land. With mustards, this will find some already in bloom. With ragweed, it is best to spray before the stems of the plants become hardened. With other weeds, of which these two are the type, as well as with these, it is often profitable to make an extra earlier spraying than that designated. For perennial sow-thistle, wild lettuce, and orange hawkweed, the spraying in grain-fields should precede the blooming of the plants, and in cases of bad infestation with perennial sow-thistle or the golden hawkweed, two sprayings should be made before the grain occupies the land. It is not clear just what can be done in the handling of bindweeds in grain-fields, but similar principles will apply. For spraying in timothy or other grass meadows to kill white-top, yarrow, self-heal, ox-eye daisy, and a number of meadow weeds, the principle is similar to that stated for grain-fields, namely, to spray thoroughly just before the grass begins heading out. This will be during late May and early June for Ohio.

In spraying pastures to check weeds, the maximum returns will usually come from a beginning application in late June or early July before many weeds are coming to bloom. After the initial application, the spraying should be repeated as often as there is development of new foliage to a marked degree.

In general, better results are secured from applications made in cloudy weather, although any weather, except that followed by rain, is satisfactory.