446 ^^V ECONOMIC ENTOMOLOGY. 



Caustic soda ox potash at the rate of one pound in from one to 

 five gallons of water makes an excellent winter wash for tree 

 trunks and branches, cleaning them of abnormal vegetable 

 growths, destroying fungus spores, and many of the insects that 

 hibernate on rough or lichen-covered bark. As against some of 

 the thinner scales it forms an excellent protection, but as against 

 the more densely armored forms it is useless. 



On the Pacific coast resin washes are much used against scale 

 insects, usually with good results ; but in the East the mixtures 

 have not met with such favor. 



A good summer wash is made as follows : 



Resin 20 pounds 



Caustic soda, 70 per cent, or above 5 pounds 



Fish-oil 3 I'i'its 



Water sufficient to make . . 100 gallons 



This is effective against scale larvae and recent sets, plant-lice, 

 and other species of that character. It acts by clogging the 

 breathing pores, and sometimes by sealing recent sets to the sur- 

 face, this latter effect being much more marked in dry regions 

 than in those that are moist or rainy. It may be safely applied 

 to the- foliage of most fruit trees. 



The winter wash is as follows : 



Resin 3° pounds 



Caustic soda, 70 i)er cent, or over 9 pounds 



Fish-oil aYz pints 



Water sufficient to make 100 gallons 



This is really a thin varnish, and is fatal to foliage and young 

 shoots when applied at other than the dormant stage. As a 

 varnish it is readily soluble in water, hence in the wet East is not 

 so effective as in the dry West and Southwest. 



To make these washes boil all the ingredients together with 

 about twenty gallons of water until thoroughly dissolved, adding 

 hot water from time to time as needed, but never enough to stop 

 the boiling after it once begins. Three hours will be required for a 

 complete mixture, hot water to make up fifty gallons being gradu- 

 ally added, and the stirring continuous. After this the balance 

 of the one hundred gallons may be added in cold water. 



All soaps have an insecticide value, and they usually kill by 



