﻿THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 37 



able hibernating quarters. Hence too much should not be expected 

 of this destruction of leaves and trash on a limited scale, since in the 

 following spring the adults are likely to swarm back into the vine- 

 yards from areas not included in the cleaning-up process. 



SPRAY TREATMENT. 



During recent years a great deal of attention has been given to 

 combating this pest by means of liquid sprays. Owing to the agility 

 of the winged adults, and also to the fact that their sloping wing 

 covers protect their soft bodies from the killing action of spray 

 liquids not sufficiently caustic to injure the foliage of the grapevines, 

 it is a very difficult task to destroy many of them with liquid spray 

 applications. This was demonstrated by Prof. Slingerland in his 

 field experimental work in the vineyards of Chautauqua County, 

 N. Y., during the outbreak of 1901-2. Since it frequently happens 

 that during seasons of heavy infestation the hibernating adults 

 appear on 'the new foliage in injurious numbers and cause consider- 

 able alarm among the vineyardists, he attempted to combat them by 

 means of a kerosene and water spray. He found, however, that the 

 margin between the percentage of oil necessary to kill the adults and 

 the percentage that would seriously injure the grape foliage was so 

 small that more injury to the vines was likely to occur than would 

 offset the benefit derived from the number of flying adults that were 

 killed by the process. 



Much greater success, however, was secured by him in spray appli- 

 cations made against the nymphs by the use of whale-oil soap at 

 a strength of 1 pound of the soap to 10 gallons of water. With 

 this spray liquid he was able, by one thorough application when the 

 majority of the nymphs were present on the foliage, to reduce their 

 numbers to such an extent that those remaining caused no serious 

 injury to the vines for the remainder of the season. 



In experiments with liquid sprays consisting of 1 pound of whale- 

 oil soap to 15 gallons of water Mr. Quayle was able to destroy a very 

 large percentage of the nymphs infesting grapevines in California. 

 He was also able to obtain good results by the use of a spray consist- 

 ing of 1 pound of resin to 15 gallons of water, using enough lye or 

 potash completely to dissolve the resin. This required 1 pound of 

 lye to about 8 pounds of resin. 



The chief objections to the use of whale-oil soap are the very 

 offensive odor connected with its application and the fact that since 

 the vines have to be thoroughly drenched with the spray in order to 

 strike the underside of all of the leaves, the clusters of grapes are also 

 necessarily drenched. This soapy liquid has a tendency to form in a 

 drop on the lower part of each berry, and after the moisture has evap- 

 orated a white stain remains which makes an undesirable discolora- 



