My attention was attracted to potash salts as an insecticide, by the casual remark of an intelligent farmer, that washing his young pear trees with a muriate of potash solution cleared them of scales. The value of this substance for insecticide purposes, should its powers be sufficient, struck me at once, and I began investigation. It was unluckily too late in the season for field experiments of the nature desired; but it is the uniform testimony of farmers who have used either the muriate or the kainit in the cornfields, that they have there no trouble with grubs or cut worms. Mr. E.B. Voorhees, the senior chemist of the station, assures me that on his father's farm the fields were badly infested, and replanting cornhills killed by grubs or wire worms was a recognized part of the programme. Since using the potash salts, however, they have had absolutely no trouble, and even their previously worst-infested fields show no further trace of injury. The same testimony comes from others, and I feel safe in recommending these salts, preferably kainit, to those who are troubled with cut worms or wire worms in corn.
A lot of wire worms (Iulus sp.) brought in from potato hills were put into a tin can with about three inches of soil and some potato cuttings, and the soil was thoroughly moistened with kainit, one ounce to one pint of water. Next morning all the specimens were dead. A check lot in another can, moistened with water only, were healthy and lived for some days afterward.
A number of cabbage maggots placed on the soil impregnated with the solution died within twelve hours.
To test its actual killing power, used the solution, one ounce kainit to one pint water, to spray a rose bush badly infested with plant lice. Effect, all the lice dead ten hours later; the younger forms were dropping within an hour.
Sprayed several heads of wheat with the solution, and within three hours all the aphides infesting them were dead.
Some experiments on hairy caterpillars resulted unsatisfactorily, the hair serving as a perfect protection against the spray, even from the atomizer.
To test its effect on the foliage, sprayed some tender shoots of rose and grape leaves, blossoms, and clusters of young fruit. No bad effect observable 24 hours later. There was on some of the leaves a fine glaze of salt crystals, and a decided salt taste was manifest on all.
Muriate of potash of the same strength was tested as follows: Sprayed on some greenhouse camellias badly infested by mealy bugs, it killed nearly all within three hours, and six hours later not a living insect was found. The plants were entirely uninjured by the application.
Thoroughly sprayed some rose bushes badly infested with aphides, and carried off some of the worst branches. On these the lice were dead next morning; but on the bushes the effect was not so satisfactory, most of the winged forms and many mature wingless specimens were unaffected, while the terminal shoots and very young leaves were drooping as though frosted. All, however, recovered later.
The same experiment repeated on other, hardier roses, resulted similarly so far as the effect on the aphides was concerned, but there was no injury to the plant.
Used this same mixture on the caterpillars of Orgyia leucostigma with unsatisfactory effect, and with the same results used it on a number of other larvae. Used on the rose leaf roller, Cacaecia rosaceana, it was promptly effective.
Tested for injury to plants, it injured the foliage and flowers of wisteria, the younger leaves of maple and grape, and the finer kinds of roses.
From these few experiments kainit seems preferable to the muriate, as acting more effectively on insects and not injuriously on plants. For general use on plants it is not to be recommended. It is otherwise on underground species, where the soil will be penetrated by the salts and where the moisture evaporates but slowly, and the salt has a longer and better chance to act. The best method of application would be a broadcasting in fertilizing quantity before or during a rain, so as to carry the material into the soil at once. In cornfields infested with grubs or wire worms, the application should be made before planting. Where it is to be used to reach root lice, it should be used when the injury is beginning. When strawberry beds are infested by the white grub, the application should be made when cultivating or before setting out.
The potash salts have a high value as fertilizers, and any application made will act as a stimulant as well as insecticide, thus enabling the plants to overcome the insect injury as well as destroying the insect.
In speaking on this subject in Salem county, I learned from farmers present that those using potash were not troubled with the corn root louse to any extent, and also that young peach trees have been successfully grown in old lice-infested orchards, where previously all died, by first treating the soil with kainit of potash.By John B. Smith, entomologist. Potash as an insecticide is not entirely new, but has never been brought out with the prominence I think it deserves. - N.J. Ag. Col. Exp. St., Bulletin 75.
A meteorological station has been built on Mont Blanc, at an elevation of 13,300 feet, under the direction of M. Vallot. It required six weeks to deliver the materials. The instruments are self-registering and are to be visited in summer every fifteen days if possible, the instruments being left to register between the visits. In the winter the observatory will be entirely inaccessible. This is the highest scientific station in Europe, but is 847 feet lower than the Pike's Peak station in Colorado.