FUNGICIDES AND THEIR APPLICATION loi 



Formalin has latelj^ been found to have some appHcation as a 

 spray. E. Levin reports highly successful control of bacterial 

 soft rot of lettuce obtained by spraying diseased plants with 

 0.4 formalin (i oz. to I2| pints), while the addition of formalin 

 to Bordeaux mixture was at one time claimed to have given 

 promising results in the control of citrus canker in the Philippines. 

 SiilpJmric Acid. 



Treatment of seeds with concentrated sulphuric acid is a 

 means of disinfection particularly valuable in some instances, as 

 with cotton seed, and with most kinds, so far from being injurious, 

 hastens and increases germination if carried out for the right 

 length of time. The seed to be treated is well stirred in a glass 

 or stone jar with a quantity of undiluted acid sufficient to cover 

 it and to give freedom of movement. The commercial grade of 

 acid is suitable. After 15 to 45 minutes' soaking (according to the 

 resistance of the seed to injury) the contents of the jar are poured 

 through a strainer of wire gauze and the seed then washed in a 

 liberal amount, preferably a stream, of water. It may be sown at 

 once or dried. This method is recommended to be used for cotton 

 seed whenever possible, as it clears away all the lint and fuzz. 

 Copper Sulphate. 



One or two per cent, solutions of copper sulphate (1-2 lb. to 

 5 gallons) are used for the disinfection of seeds, especially of 

 grain for smuts. Preferably the grain is immersed in a barrel 

 of the solution, the floating matter skimmed off, and then the 

 seed quickly dried and sown. Another method is to sprinkle 

 a heap of seed with the solution, turning and mixing until all is 

 wetted, then drying. If the seed is treated with weak milk of 

 lime after the copper solution there is less resulting injury. 

 Bleaching Powder. 



The so-called chloride of lime or bleaching powder has recently 

 been recommended as very effective for disinfecting some kinds of 

 seeds. The method of preparation advised by J. K. Wilson is as 

 follows : — " 10 grams of commercial chloride of lime (titrating 

 28 per cent, chlorine) is mixed with 140 cc. of water, (5 oz. to 

 3I pints). The mixture is then allowed to settle for five or ten 

 minutes and the supernatant liquid decanted off or filtered. 

 The solution or filtrate, which contains about 2 per cent, chlorine, 

 is used as the disinfectant. The volume of the solution employed 

 should be about five times or more the volume of the seed." The 

 permissible period of exposure must be learnt by experiment 

 for each kind of seed. Washing is not necessary. 



Bleaching powder has recently been mentioned as a disin- 

 fectant for soil. 



Eaii de Javelle. 



Recent experiments by Duggar and Davis indicate that com- 

 mercial Javelle water (chlorinated potash), diluted i in 10 and 

 used for soaking seeds for 3 hours or upwards, may prove an 

 exceedingly effective means of seed sterilisation. 



