SPBAYING AGAINST GRAPE LEAFHOPPEE. 13 



(See fig. 3.) At this time the underside of badly infested leaves will 

 be covered by the nymphs in all stages of development. Generally 

 speaking, this condition is likely to occur in the Lake Erie Valley from 

 July 1 to 15. All of the field experiments conducted in 1910 and 1911 

 were made between these dates and in every instance very satisfactory 

 results were secured. Since the nymphs continue to hatch over a 

 long period, if the spray application is made while the first nymphs 

 to hatch are quite small large numbers are likely to hatch after the 

 spray application has been made, thus necessitating a second applica- 

 tion a few weeks later. On the other hand, if the application is with- 

 held until many of the nymphs have developed wings it is doubtful 

 if large vineyard areas can be treated before a large percentage of 

 the nymphs have reached the winged stage. For it must be under- 

 stood that the tobacco extracts at the dilutions recommended are 

 effective only against the wingless nymphs infesting the underside of 

 the grape foliage. Where it is necessary to treat large areas for this 

 pest, observation would indicate that spray applications should 

 commence during the first week in July. 



Observations on the abundance and the extent of injury wrought 

 by this insect pest of the grapevine in the vineyard areas of New York, 

 Pennsylvania, and Ohio bordering on Lake Erie, and also in the vine- 

 yard areas of Michigan, indicate that its depredations have increased 

 during the past few years. Progressive vineyardists are commencing 

 to realize that the accumulated injury to the vines by this pest is 

 responsible for curtailment in crop yield and inferiority in quality of 

 fruit wherever it is present on grapevines in large numbers and that 

 steps must be taken to accomplish its control. It is for this reason 

 that the experiments presented in this paper were undertaken, and 

 it is hoped that the results obtained are of sufficient commercial value 

 to encourage grape growers having vineyard areas infested by the 

 grape leafhopper to adopt this method of control. 



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