﻿THE GRAPE LEAFHOPPEK IN THE LAKE ERIE VALLEY. 41 



cess with any typo of spray apparatus in present use in work against 

 this pest appears to depend more on the care and ingenuity of the 

 individual operator than upon the great superiority of any given type 

 of machine over another. 



RECOMMENDATIONS. 



Efforts to control the depredations of the grape leafhopper by the 

 destruction of the winged adults, by burning over or cleaning up 

 their hibernating places adjacent to vineyards, by trapping them on 

 sticky shields, or by endeavoring to treat them with contact sprays 

 when they appear on the new growth of the grapevines in spring 

 before oviposition takes place, have proven far from satisfactory. 

 Although these methods may furnish a certain measure of relief over 

 very limited areas, they are of very slight practical value as control 

 measures when serious infestations occur in large, vineyards. 



Observations indicate that except in seasons of extremely heavy 

 infestation, or over limited areas, the injury wrought by the over- 

 wintering adults in spring to the new growth is not likely to reduce 

 greatly the entire seasonal growth of the infested grapevine provided 

 a large percentage of their offspring in the form of nymphs can be 

 destroyed before they reach the adult stage. In other words, it is 

 the steady drain made on the infested grapevines from the time the 

 overwintering adults attack them in spring, combined with the 

 unchecked attack of the nymphs and adults of the new brood until 

 late September, that results in serious injury by curtailing the size of 

 the crop and the growth of the vine. 



That the nymphs can be controlled by the spray method has been 

 thoroughly demonstrated. Successful control of the nymphs by this 

 method depends on thoroughly wetting all parts of the underside of 

 the infested leaves with the spray liquid. 



Tobacco extracts have given excellent results, used according to 

 the following formulas : 



I. Tobacco extract containing 2.70 per cent nicotine sulphate, diluted at the ratio of 

 1 part to 150 parts of water. 



II. Tobacco extract containing 40 per cent nicotine sulphate, diluted at the ratio of 

 1 part to 1.500 parts of water. 



The killing quality of the tobacco extract is apparently just as 

 effective when added at the same dilution to the Bordeaux mixture 

 and arsenate of lead spray liquids, which are used to control fungous 

 diseases and chewing insect enemies of the grapevine, as when used 

 with clear water. No injury results from combining these spray 

 mixtures, namely, tobacco extract, Bordeaux mixture, and arsenate 

 of lead. However, the tobacco extract should not be mixed with 

 spray mixtures containing arsenicals in the form of Paris green or 

 arsenite of lime, for serious injury to the foliage is likely to occur as 

 a result of the combination. 



