DISEASES AND INSECTS 



DISEASES AND INSECTS 1043 



Hellebore. Hellebore is a light brown powder made from the 

 roots of the white hellebore plant (Veratrum album), one of the lily 

 family. It is applied both dry and in water. In the dry state, it 

 is usually applied without dilution, although the addition of a 

 little flour will render it more adhesive. In water, four ounces of 

 the poison is mixed with two or three gallons, and an ounce of glue, 

 or thin flour paste, is sometimes added to make it adhere. A decoc- 

 tion is made by using boiling water in the same proportions. Helle- 

 bore soon loses its strength, and a fresh article should always be 

 demanded. It is much less poisonous than the arsenicals, and 

 should be used in place of them upon ripening fruit. It is used for 

 various leaf-eating insects, particularly for the currant-worm and 

 rose -slug. 



Contact insecticides. 



The most important contact insecticides are soaps, sulfur, sul- 

 fur compound, and oily or resinous emulsions. 



Soaps. The most commonly used soap solution is that pre- 

 pared from fish-oil soap. The commercial brands of this soap are 

 usually by-products and contain many impurities; further, many 

 of them contain an excess of free or uncombined alkali and are thus 

 likely to injure young and tender foliage. A good fish-oil soap may 

 be prepared by the following formula: Carstic soda, six pounds; 

 water, one-half gallon; fish-oil, twenty-two pounds. Dissolve the 

 caustic soda in the water and then add the fish-oil gradually under 

 constant and vigorous stirring. The combination occurs readily at 

 ordinary summer temperatures, and boiling is unnecessary. Stir 

 briskly for about twenty minutes after the last of the oil has been 

 added. There is now on the market a good brand of insecticide 

 soap prepared from cotton-seed oil soap stock or from an impure 

 grade known as pancoline. 



Sulfur. Sulfur may be obtained in two forms, flowers of sul- 

 fur and flour of sulfur. In the form of a powder or dust, sulfur is 

 especially valuable against red-spider. In California, flowers of 

 sulfur mixed with equal parts of hydrated lime is blown on the 

 trees for the control of red-spider and mite. It may also be used for 

 the same purpose mixed with water at the rate of one pound in 

 three gallons of water, to which has been added a little soap to 

 keep the sulfur in suspension. The mixture should be agitated 

 constantly during spraying. The sulfur remains longer in sus- 

 pension if it is first made into a paste with water containing 

 one-half of 1 per cent of glue. Page 1028. 



Lime-sulfur solution. A solution of lime-sulfur was first used 

 as an insecticide in California in 1886. It is now the standard 

 remedy for blister mite, San Jos6 scale and similar scales, as well 

 as an efficient fungicide. The lime-sulfur solution may be pur- 

 chased in the concentrated form or may be prepared as follows: 

 Lump lime (95 per cent calcium oxid), thirty-eight pounds; lump 

 lime (90 per cent calcium oxid), forty pounds; sulfur, eighty pounds; 

 water, fifty gallons. Make a paste of the sulfur with about ten 

 gallons of hot water. Add the lime. As the lime slakes, add hot 

 water as necessary to prevent caking. When the lime has slaked, 

 add hot water to make fifty gallons and boil one hour, stirring con- 

 stantly. Water should be added from time to time to keep the 

 liquid up to fifty gallons. Store in air-tight hardwood barrels. 

 Test the strength of the solution with a Baum6 hydrometer and 

 dilute for use according to the following table (see also p. 1029) : 



DILUTIONS FOB DORMANT AND SUMMER SPRAYING WITH 

 LIME-SULFUR MIXTURES 



Emulsions. Emulsions are oily or resinous sprays in which 

 these substances are suspended in water in the form of minute 

 globules, a condition brought about by the addition of soap. They 

 form an important class of contact insecticides, useful particularly 

 against scale insects and plant-lice. 



Kerosene emulsion. Kerosene emulsion is the oldest of our 

 contact insecticides. It is especially valuable for use against plant- 

 lice and other small, soft-bodied insects. It is prepared by the 

 following formula: Soap, one-half pound; water, one gallon; 

 kerosene, two gallons. Dissolve the soap in hot water; remove 

 from the fire and, while still hot, add the kerosene. Pump the 

 liquid back into itself for five or ten minutes or until it becomes a 

 creamy mass. If properly made, the oil will not separate on cooling. 

 For use on dormant trees, dilute with five to seven parts of water. 

 For killing plant-Jice on foliage, dilute with ten to fifteen parts of 

 water. Crude-oil emulsion is made in the same way by substitu- 

 ting crude oil in place of kerosene. The strength of oil emulsions is 

 frequently indicated by the percentage of oil in the diluted liquid: 

 for a 10 per cent emulsion, add seventeen gallons of water to three 

 gallons of stock emulsion; for a 15 per cent emulsion, add ten and 

 one-half gallons of water to three gallons of stock emulsion; for a 

 20 per cent emulsion, add seven gallons of water to three gallons 

 of stock emulsion; for a 25 per cent emulsion, add five gallons of 

 water to three gallons of stock emulsion. 



Distillate emulsion. Distillate emulsion is widely used 

 in California. Distillate (28 Baume), twenty gallons; whale-oil 

 soap, thirty pounds; water, twelve gallons. Dissolve the whale- 

 oil soap in the water which should be heated to the boiling point, 

 add the distillate and agitate thoroughly while the solution is hot. 

 For use, add twenty gallons of water to each gallon of the stock 

 solution. 



Carbolic acid emulsion. This spray is used in California for 

 mealy-bugs, plant-lice, and the soft brown scale: Whale-oil soap, 

 forty pounds; crude carbolic acid, five gallons; water, forty gallons. 

 Dissolve the soap completely in hot water, add the carbolic acid, 

 and heat to the boiling point for twenty minutes. For use, add 

 twenty gallons of water to each gallon of stock solution. 



Miscible oils. There are now on the market a number of con- 

 centrated oil emulsions, known as soluble or miscible oils, intended 

 primarily for use against the San Jos6 scale. For this purpose they 

 are fairly effective when diluted with not more than fifteen parts of 

 water. To lessen danger of injury to the trees, applications should 

 not be made when the temperature is below freezing, nor when the 

 trees are wet with snow or rain. Methods have been devised 

 for preparing these concentrated emulsions at home, but as there 

 is considerable danger attending the process, it is better to buy 

 them ready-made. 



Tobacco. Tobacco is one of our most useful insecticides. The 

 poisonous principle in tobacco is an alkaloid nicotine, which in 

 the pure state is a colorless fluid; slightly heavier than water, of 

 little smell when cold and with an exceedingly acrid burning 

 taste even when largely diluted. It is soluble in water and entirely 

 volatile. It is one of the most virulent poisons known; a single 

 drop is sufficient to kill a dog. Commercial tobacco preparations 

 have been on the market for many years. The most important of 

 these are black leaf, "black leaf 40," and nicofume. 



Black Leaf. Black leaf was formerly the most widely used 

 tobacco extract. It contains only 2.7 per cent nicotine and has now 

 been replaced by the more concentrated extracts. It is used for 

 plant-lice at the rate of one gallon to sixty-five gallons of water. 



"Black leaf 40." "Black leaf 40" is a concentrated tobacco 

 extract containing 40 per cent nicotine sulfate. Its specific gravity 

 is about 1.25. In this preparation the nicotine is in a non-volatile 

 form, it having been treated with sulfuric acid to form the sulfate. 

 "Black leaf 40" is used at strengths varying from one part in 800 

 parts of water to one part in 1,600 parts. It can be satisfactorily 

 combined with other sprays, as for example, lime-sulfur solution, 

 arsenate of lead, and the various soap solutions. When used with 

 water, about four pounds of soap should be added to make the 

 mixture spread and stick better. 



Nicofume is a tobacco extract containing 40 per cent of nicotine 

 in the volatile form. It is intended primarily for use in greenhouses. 

 Strips of paper soaked in this preparation are smudged in green- 

 houses to destroy aphids. 



Tobacco is also used in the form of dust for the same purpose. 

 It is especially valuable against root-lice on asters and other plants. 

 Tobacco extracts can be made at home by steeping tobacco sterna 

 in water, but as they vary greatly in nicotine content and are 

 sometimes likely to injure tender foliage, it is better to buy the 

 standardized extracts. 



Pyrethrum. A very fine, light brown powder, made from the 

 flower-heads of species of pyrethrum. It is scarcely injurious to 

 man. Three brands are on the market: 



Persian insect-powder, made from the heads of Pyrethrum 

 roseum, a species also cultivated as an ornamental plant. The 

 plant is native to the Caucasus region. 



Dalmation insect-powder, made from Pyrethrum cinerarix- 

 folium. 



Buhach, made in California from cultivated plants of Pyrethrum 

 cinerarise folium. 



When fresh and pure, all these brands appear to be equally 

 valuable, but the home-grown product is usually considered most 

 reliable. Pyrethrum scon loses its value when exposed to the air. 

 It is used in various ways: 



(1) In solution in water, one ounce to three gallons. Should 

 be mixed up twenty-four hours before using. 



(2) Dry, without dilution. In this form it is excellent for thripa 

 and lice on roses and other bushes. Apply when the bush is wet. 

 Useful for aphis on house plants. 



(3) Dry, diluted with flour or any light and fine powder. The 

 poison may be used in the proportion of one part to from six to 

 thirty of the dilutent. 



(4) In fumigation. It may be scattered directly upon coals, or 

 made into small balls by wetting and molding with the hands and 



