Paris Green, a stomach poison which has been used extensively for many years in combating chewing insects. In order to prevent injury to foliage, it is always desirable to add some lime in the preparation of the spray. One pound of lime and one pound of paris green are used with 75. to 200 gallons of water, depending upon the susceptibility of the foliage to burning. It is always safer to have a slight excess of lime in the mixture. The paris green becomes more thoroughly diffused in the water if it is first mixed to a paste. As it is simply held in suspension and as it sinks quickly, the spray pump should be provided with an agitator to keep the mixture constantly stirred while being applied.
White hellebore finds favor among some home gardeners mainly because it soon loses its poisonous principle when exposed to the air. As a stomach poison it is effective for cabbage worms and other pests, if the material is fresh when applied. It may be used as a powder, but the distribution is more thorough if applied as a spray, using « to 2 ounces of powder in 2 gallons of water.
Kerosene Emulsion is probably the most extensively used of contact poisons for sucking insects. It is prepared as follows: Dissolve « pound of hard, soft or whale-oil soap in a gallon of hot water; while hot, add 2 gallons of kerosene. Then use a force pump provided with a direct nozzle to churn or agitate violently for 5 or 10 minutes, or until the mixture is of the consistency of thick cream. If thoroughly emulsified the oil will not separate and the stock solution may be kept almost indefinitely. Various dilutions, ranging from 10 to 20 parts of water, with one of the stock solution, are used for various sucking insects. It is essential, of course, that the emulsion come in contact with the enemy. This is not always easy to accomplish, especially when the insects are on the undersides of the leaves.
As a contact poison and a repellent carbolic acid emulsion is valuable in combating root maggots of various crops, such as onion, radish and cabbage. It is made in the same manner as kerosene emulsion (132), by using 1 pound of soap, I gallon of water and 1 pint of crude carbolic acid.
Tobacco is used in various forms. The powder is often effective in destroying plant lice. Stems are sometimes strewn along the lines of peas to repel the pea louse. Tobacco decoction, made by steeping or soaking the stems in water, is an excellent insecticide for plant lice. Numerous nicotine extracts and powders have been placed on the market and are used for the various species of aphides.
Whale-oil soap, 1 pound dissolved in 5 to 7 gallons of water, makes a useful insecticide to control aphides and other minute insects. Hard and soft soaps may be substituted, but whale-oil soap makes a more effective spray.
Numerous other materials are sometimes used in arresting the ravages of injurious insects. Lime, ashes, bordeaux mixture and sulphur may be classed among insect repellents. A formalin solution prepared by mixing I pint of a 40 per cent solution with 30 to 40 gallons of water is valuable in treating potatoes both for scab and the potato scab gnat. Both cold and hot water are used in destroying plant lice, but hot water is far more effective. Plants will stand water heated to temperatures ranging from 125 to 180 degrees The hot water treatment is especially desirable to check lice on a small number of cabbage plants in the home garden. Pyreth-rum or insect powder is also effectual in destroying some insects by closing their breathing pores. It is generally used as a powder, but may also be mixed with water and applied as a spray.
Although other fungicides are used sometimes in vegetable gardening, this is the standard spray for the control of fungous diseases of vegetables. The usual formula is: 4 pounds of lime, 4 pounds of copper sulphate (bluestone) and 50 gallons of water.
It is convenient to keep stock solutions of both the bluestone and the lime. To make a stock solution of bluestone, use 2 pounds of bluestone to the gallon of water. The lime should be slaked and kept as a thin paste. Both solutions should be covered to prevent evaporation. For the formula stated, add 2 gallons of the bluestone solution to 25 gallons of water and then introduce the lime paste diluted with the other 25 gallons. When insufficient lime is used there is danger of burning the foliage of many plants. To make certain of adding enough lime the ferrocyanide test should be employed. This may be done as follows: Dissolve an ounce of potassium ferrocyanide or yellow prussiate of potash in a pint of water; place in a bottle and label "poison." Stir lime solution into the diluted bordeaux mixture until the ferrocyanide solution will not turn brown when a drop or two is added from the bottle. It is always safer to have an excess of lime. As bordeaux mixture deteriorates upon standing, it should be used promptly after mixing.
It is difficult to cause solutions or mixtures to adhere to the leaves of some plants; for example, the onion and cabbage. To obviate this trouble, a "sticker" may be made of 2 pounds of resin, 1 pound of sal soda crystals and 1 gallon of water. This mixture is boiled out of doors from 1 to 1« hours, or until the solution is of a clear brown color, and then added to every 50 gallons of bordeaux mixture and to every 100 gallons of other spray materials.