20 ALFRED E. CAMERON. 



The experiments with various fungicides and insecticides were carried out in the 

 State of New Jersey. They were intended to demonstrate how a larger yield of 

 potato tubers per acre might be procured by the employment of scientific methods- 

 of spraying and dusting. 



The principal fungus diseases attacking the potato are early blight {Macrosporium 

 solani), late blight {Phytophthora infestans), and dry rot (Fusarium oxysporum). 

 Late blight, which levies a heavy toll on the potato crop in America, is injurious in 

 New Jersey only in exceptionally wet seasons. A pathological condition of the 

 leaves known as " tip-burn " is in some years responsible for a reduced yield. 



Of the various treatments applied, Bordeaux mixture vindicated itself in each case. 

 It is not only a most excellent fungicide, but also an effective insecticide when arsenate 

 of lead is added. Both the Colorado and flea-beetles were better controlled by the 

 Bordeaux-lead arsenate mixture than by any of the other insecticides used in the 

 field experiments. 



Bordeaux mixture acts as a plant stimulant by maintaining the green colour of 

 the leaves for a longer period. This naturally means larger tubers. 



Thoroughness of application of the Bordeaux mixture and frequent repetition 

 of the treatment, at least once every ten days, are necessary for effectiveness. Care 

 in its preparation is strongly advised. Sufficient lime must be used to ensure that 

 all the copper sulphate is changed to the hydrate form, otherwise burning of the 

 leaves may ensue. 



The use of Bordeaux mixture may increase the value of the yield of tubers anything 

 from £3-£5 per acre. The increase, however, varies considerably in different localities, 

 and in different years. 



Sulphur did not quite realise expectations as a crop stimulant. Various proprietary 

 Bordeaux mixtures proved less economical and less efficient than the home-made 

 article. 



The cost of spraying or dusting varies according to the locality, but of all the 

 treatments applied, home-made Bordeaux mixture always proved cheapest. 



Concurrent experiments carried out in the laboratory and field with many insecti- 

 cides additional to those used in the large field tests, were the means of discovery 

 of an insecticide which seemed to fulfil all requirements in controlling the flea-beetle. 

 It is composed of a combination of pyrethrum infusion, gelatin or soap, and lead 

 arsenate. Extended trial will, however, have to be made to establish its efficacy. 



The fenestration of the leaves by the flea-beetle, besides materially reducing the 

 assimilating surface of the leaves, also renders the injured tissue more susceptible 

 to the attack of various cryptogamic diseases. This is notoriously true of early bfight. 



Counts made of the fenestrations of the leaves on a large number of shoots, gave 

 an idea of the intensity of the damage caused by the flea-beetle at any one period. 

 A comparison of the counts made on plants treated with different substances, supplied 

 a rough estimate of their value in controlling the pest. 



For a true interpretation of the results of the field experiments various factors 

 must be considered, amongst which not least are the physical and chemical conditions, 

 of the soil, previous cultivation and the vagaries of the weather. 



