Warren Sheaf

ERADICATION OF THE SOW-THISTLE

R. S. Dunham, Northwest School Agronomist, Offers Advice.--Continuous Fight Necessary.

No half-way measures will succeed in the fight against the sow thistle according to R. S. Dunham, agronomist at the Northwest School and Station, Crookston. The battle must be relentless and continuous for sow thistle does not succumb to intermittent attacks. It has as many lives as there are new plants from its rootstocks. Ten have been found on a single running root.

The important facts about this plant to be recognized in waging a fight to death are, first, that it is propagated both by seed and by underground root stocks: second, that it is in its weakest condition when preparing to blossom, and third, that it cannot live without leaves.

Of equal importance are the two necessary campaign plans. These consist of, first, complete eradication and, second, control. As in all troubles of life, "an ounce of prevention is worth a pound of cure." Preventive measures are necessary: the plant should not be allowed to produce seed and only crops seed free from this weed should be planted. Sow thistle should be cut as near to blossoming time as can be done without danger of allowing some plants to mature seed. Since the blossoms may mature seed after they are cut at this stage, all plants should be burned immediately after cutting.

Further eradication of the weed depends upon killing its root-stocks. These can only be killed by preventing them from producing leaves. The leaves of the plant are necessary to convert the plant food taken up by the roots into a form that nourishes the plant. Without leaves the plant must die. For that reason, fallowing is essential to complete eradication.

There are three kinds of fallow as practiced by the farmer: the one consists of plowing with no cultivation, the second consists of plowing and occasional cultivation in which new plants are allowed to produce their first leaves, and the third consists of plowing and sufficient cultivation to keep all leaves from forming "the black fallow." Only the latter kind is worth while.

Plowing shallow in the fall or discing will aid the seeds scattered in the fall to germinate and frosts will kill them. The following spring the land should be plowed at the normal depth and a black fallow maintained by cultivation until freeze-up.

The plowing should be well done. All land should be cut by the share and loosened by the mouldboard including the dead furrow. The first two furrows should be plowed shallow and thrown out. Later they should be plowed back at the normal depth. Leave no unplowed strips in the field or at the headlands. Cover all weeds.

The make of the cultivator is not as important as the type. It should have shares that overlap, have sharp cutting edges, and run level. The duckfoot type is satisfactory. The disc-harrow is very unsatisfactory and the spike-tooth harrow is fairly satisfactory if precaution is taken not to drag the roots over the field.

There are several agencies of seed distribution that cannot be prevented: wind, water, and railroads scatter seeds. For this reason control measures must be used by the farmer after his eradication of the weed. Chief of these are crop rotation and good cultivation. The rotation should include a cultivated crop, a grass or legume crop, and a grain crop. Corn is an excellent cultivated crop and sweet clover heads the list of legumes. Winter rye is one of the best weed control crops that can be grown because it ripens before the thistle blossoms.