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 EVALUATION OF PURATIZED AGRICULTURAL SPRAY ^ AN ERADICANT FOR APPLE SCAB 



Science has been searching for the ideal fungicide for controlling apple scab. 

 Since 1908 when liquid lime sulfur came into use as a funt,icide for scab, to replace 

 Bordeaux mixture, notable progress has been made in this direction. This article 

 is written to consider the usefulness and limitations of puratized Agricultural 

 Spray, 



This material has good scab-protective and curative values. It is expensive. 

 As a protectant for scab it gives no better control than high grade v/ettable sulfur, 

 vjhich is much cheaper. For that reason its use as a protectant spray is not 

 encouraging. Under most conditions it is non-injurious to the trees and it is 

 compatible viith sulfur, Fermate, Nicotine sulfate and lead arsenate. As a curative 

 spray for scab, on the basis of the writer's research work at Walthara, it is 

 superior to liquid lime sulfur, its only competitor, Hov/ever, its action as an 

 eradioant or curative is intriguing. Inconsistent curative results are reported 

 by growers, and to explain these discrepancies statements have been mads that 

 sulfur, lime, hard water, magnesium and clay in the v;ater invalidate or depreciate 

 the toxicity of puratized. Some of us even think that the variable results are due 

 in part to the age of the scab spots, the younger infections yielding and the older 

 ones not yielding; also that the absorption of puratized by the scab fungus in 

 lethal amounts is influenced by the physiology of the scab fungus or the leaf cells 

 on which it forages. Changes in the chemical composition of the product itself 

 cannot be ignored in searching for the answer to the problem. 



The age of the scab legion is not necessarily a criterion. Scab spores in 

 all ages of foliage lesions are killed. Nevertheless, it is best to spray the trees 

 to eradicate scab at the calyx period or very soon thereafter to prevent the scab 

 from parasitizing the loaf tissue to the killing point, and from sporulating 

 further, 



Puratized Agricultural Spray should not be used after June 15 nor beyond 

 20 days after calyx. This is a precautionary measure intended to prevent any 

 possibility of tainting the harvested fruit with mercury. Since in this period 

 both primary and secondary scab of various ages of infection are apparent, this is 

 the appropriate period to eradicate foliage spots. Eradication of these infections 

 with Puratized is ultimately complete. 



The lethal action of Puratized on the scab fungus is not necessarily immediate, 

 Ilany growers have been disappointed because spore germination tests after treat- , 

 xaent have indicated a negative or incomplete result. Eventually and in most cases, 

 however, scab is satisfactorily arrested. 



There is indication that lime and bentonite weaken the action of Puratized. 

 The addition of one half the formula of v/ettable sulfur to 1 pint of Puratized can 

 be an advantage on the basis of tests in 1947. Paste sulfur or a high grade dry 

 wettable sulfur free of bentonite or similar inert material is preferred. Fermate 

 1/2 lb, may be substituted for sulfur with the promise of even better control of 

 foliage scab, 



Puratized Agricultural Spray is a good protectant against fruit scab but it 

 will not eradicate it. Obviously then it is important to apply the Puratized 

 eradioant spray at calyx or soon thereafter to keep foliage scab from spreading to 

 the fruit. 



Finally we are still searching to leurn why the 1946 and 1947 productions of 

 Puratized Ab^icultural Spray used at the rate of 1 pint in 100 gallons have not 

 eradicated scab as promptly nor as completely as the mora concfentrt\te'i 1945 Puratizad 

 N5E, used at tne rate of I/2 pint to 100 gallcMas water, 



E. F. Guba 



