DAMPING-OFF OF CONIFEROUS SEEDLINGS. 29 



3. Copper sulphate, one-tenth avoirdupois ounce per square foot, dissolved in water 

 and applied immediately after the seed is sown and covered. 



4. Same as treatment 3, but one-sixth ounce per square foot. 



5. Zinc chlorid, five-sixteenths avoirdupois ounce per square foot, dissolved in water 

 and applied immediately after the seed is sown and covered. 



6. Formaldehyde, five-sixteenths fluid ounce per square foot, dissolved in water and 

 applied 10 days before seed is sown . Keep the bed covered with paper or tarpaulin 

 during these 10 days. Do not spade up formaldehyde beds after treatment. If 

 necessary to cover the seed with soil from outside of the plat, use subsoil just dug up 

 from at least 1 foot below the surface. 



7. Same as treatment G, but apply only three days before seed sowing and do not 

 cover beds with paper. 



8. Air-slaked lime, three-eighths avoirdupois ounce per square foot, applied dry 

 and raked into the upper 3 inches of soil just before sowing. (If hydrated lime is 

 used, three-tenths ounce per square foot will be sufficient.) Immediately after the 

 seed is sown and covered, apply one-fifth ounce of sulphuric acid per square foot, 

 dissolved in water. 



In dissolving disinfectants for sandy soils, use sufficient water to 

 make from 1 to 1|- pints of solution per square foot. One and one- 

 half pints should be used if the soil is dry; 1 pint is sufficient if the 

 soil is already wet. 



GENERAL DIRECTIONS FOR TREATMENTS. 



Commercial or technical grades of all the disinfectants are satisfac- 

 tory. The sulphuric acid purchased should be concentrated, having 

 a specific gravity of at least 1.82, while the formaldehyde solution, or 

 "formalin" as it is sometimes called, should be the strongest obtain- 

 able, so-called 40 per cent solution, containing 37 per cent by weight. 

 All disinfectants should be kept from the air as much as possible, as 

 they change in strength if exposed. Copper sulphate requires the 

 least care in this respect. Acid should be dissolved by pouring it into 

 the water — never by the reverse process. Copper sulphate is quickest 

 dissolved by putting it in a burlap sack and hanging it in the water 

 just below the surface. Both of these solutions are corrosive to metal 

 and should be handled only in wooden or earthenware containers and 

 applied with sprinklers which have been coated inside with hot 

 paraffin. 1 Acid is also hard on the hands and clothes. Men who use 

 it on a large scale are very careful to keep their shoes heavily greased. 

 Canvas gloves treated with hot paraffin or with a mixture of paraffin 

 and a lighter grease, such as vaseline or lard, should be a valuable pro- 

 tection for the hands. The charring of wooden containers used in 

 making up dilute acid solutions probably can be largely prevented by 

 washing them out well with water containing washing soda before they 



1 To coat a sprinkler with paraffin, get the cake paraffin sold by grocerymen for use in sealing jelly and 

 preserves. Shave off some of the paraffin into the sprinkler, and heat the sprinkler till all the paraffin is 

 melted. Then turn the sprinkler around so that the liquid paraffin runs over the entire inside surface 

 and finally pour what is left of the paraffin out through the spout. The whole can should be hot during 

 the process, so that the paraffin will leave a thin coating; a thick coating cracks off too easily. The holes 

 in the sprinkler head will have to be cleaned out with a pin or toothpick after the paraffin has hardened. 



