38 



INSECTS AND DISEASES 



without preventing the boiling. The mixture becomea 

 quite thin during the boiling process, and when finished is 

 of a deep orange color." 



This is one of the popular and reliable remedies for 

 San Jos§ scale. 



Fig. 56. Spore-tearing stalks of a wilt fungus (Acrostalagmus 

 albus). In this fungus the spores are borne lu heads; some 

 of the heads are ruptured at the right. (After Van Hook. ) 



Kerosene Emulsion. — Hard, soft or whale-oil soap, J 

 pound ; boiling soft water, 1 gallon ; kerosene, 2 gallons. 



Dissolve the soap in the water, add the kerosene and 

 churn with a pump for 5 to 10 minutes. Dilute 4 to 10 

 times before applying. Use strong emulsion for all scale 

 insects. For such insects as plant-lice, mealy-bugs, red 

 spider, thrips, weaker preparations will prove effective. 

 Cabbage-worms, currant-worms, and all insects which 

 have soft bodies, can also be successfully treated. It is 

 advisable to make the emulsion shortly before it is used. 

 For San Jose scale, use 1 pound of whale-oil soap and 

 dilute in proportion of one part to six of water. Especially 

 effective in summer to kill the young and tender lice. 



Miscible or "Soluble" Oils. — Recently various oils 

 that emulsify readily when poured into water have 

 been put on the market. Some persons have found 

 them to be of great value and others report poor or 

 indifferent results. Emulsified with twelve to fif- 

 teen times their quantity of water, they are applied 

 to dormant trees for scale. 



Distillate Spray. — In order to overcome some of 

 the difficulties in the making and use of kerosene 

 emulsion, California citrous growers are now using 

 a mechanical mixture of a special distillate of 

 petroleum and water. The mixture is prepared by 

 a sort of chum propelled by a gasoline engine, and 

 the same engine applies the spray. For scale 

 insects and mites on citrous fruits. 



Tobacco Water. — Prepared by placing tobacco 

 leaves and stems in a water-tight vessel, and then 

 covering them with hot water. Allow to stand sev- 

 eral hours, dilute the liquor 3 to 5 times, and apply. 

 For soft-bodied insects. 



Whale-oil Soap. — On dormant trees for San Jose 

 scale, dilute 2 pounds to 1 gallon water ; for sum- 

 mer use on scale or aphis, 1 pound to 5 to -7 gallons. 

 Dissolve in hot water if wanted quickly. 



of quicklime should be added. Repeated applications will 

 injure most foliage, unless the lime is used. Paris green 

 and Bordeaux mixture can be applied together with perfect 

 safety. The action of neither is weakened, and the Paris 

 green loses its caustic properties. Use at the rate of 4 to 

 12 ounces of the arsenite to 50 gallons of the mixture. 

 It is sometimes used as strong as 1 pound to 50 gallons, 

 but this is usually unsafe and generally unnecessary. This 

 is the old and best known insecticide, used for potato- 

 beetle, codling-moth, canker-worm, tent-caterpillar and 

 very many other insects. 



Arsenate of Lead. — See page 44. 



White Arsenic. — White arsenic, being cheaper and of 

 more constant strength than Paris green, is becoming 

 increasingly popular as an insecticide. It may be safely 

 used with Bordeaux mixture, or separately if directions 

 as to its preparation are carefully followed ; if, how- 

 ever, these are neglected, injury to foliage will result. 

 It is -unwise to use white arsenic without soda or lime. 

 Methods numbers one and two are recommended as the 

 least likely to cause injury. 



(1) Arsenite of Soda for Bordeaux Mixture. — To a 

 solution of 4 pounds salsoda crystals in 1 gallon of water, 

 add 1 pound of white arsenic and boil until dissolved. 

 Add water to replace any boiled away, so that 1 gallon 

 of stock solution of arsenite of soda is the result. Use 

 1 pint of this stock solution to 50 gallons of Bordeaux. 



(2) Arsenite of Lime. — (a) If used alone (not in con- 

 nection with Bordeaux) white arsenic should be prepared 

 thus: — To a solution of 1 pound of salsoda crystals in a 

 gallon of water, add 1 pound of white arsenic and boil 

 until dissolved. Then add 2 pounds of fresh slaked lime 

 and boil 20 minutes. Add water to make 2 gallons of 

 stock solution. Use 1 quart of this stock solution to 50 

 gallons of water. 



"f leaf 



Leaf Tissue. 



Insecticides designed for the insect to eat. 



Paris Green. — Paris green, 1 pound ; water, 75 

 to 250 gallons. 



If this mixture is to be used on fruit trees, 1 pound 



Fig. 57. How a fungus works m a leaf. Diagrammatic cross-seo- 

 m2" „* "f'"? '^''' affeo'ed l>y rust (Uromyces appendiculatus) ■ 

 Ihe cells of the leaf-tissue contain the chlorophyll grains. The 

 mycelium of the fungus is seen ramifying in the tissue The 

 spores are formed on the ends of mycelial threads, and as they 

 grow the epidermis of the leaf is pushed up and broken. (After 

 Whetzel.) 



