48 Director's Report of the 



placed upon the effects of the destructive work of the insect upon 

 the quality of the fruit, as well as on the yields, which has not been 

 fully appreciated by growers generally. It is shown that the 

 grape leaf-hopper feeds by sucking, and preferably on the under 

 sides of the leaves. It pierces the skin of the leaf, feeds until 

 satisfied and then withdraws its proboscis or sucking tube, thus 

 leaving an opening from which the plant juices dry out, not only 

 from the pierced cell but from adjoining ones. There is soon 

 formed about each puncture a spot of dead tissue. When the 

 insects are superabundant there is a severe drain on the vitality 

 of the leaf and it takes on an unhealthy yellow hue. The death 

 of so many starch-making cells lessens the amount of wood pro- 

 duced and of fruit formed; and seriously affects the quality of 

 the fruit, making it ill-flavored or sour and poorly colored. The 

 rich blue-black of the Concord becomes a lifeless reddish color 

 while the attractive flavor may be lost so that grape- juice makers 

 and most buyers of grapes for the table reject the fruit. 



Brief descriptions are given of a number of spraying experi- 

 ments which showed that a spray containing two one-hundredths 

 of 1 per ct. of nicotine (Black Leaf 40, one gallon to sixteen 

 hundred gallons of water) is the most effective and safest insecti- 

 cide for the control of this pest. The bulletin concludes with 

 general directions for spraying. The application of the mixture 

 can be done by the usual hand-spraying with trailing hose or by an 

 automatic leaf-hopper sprayer which is completely described. The 

 latter device was developed during the year's work and has proven 

 most satisfactory. With high pressure and the proper adjustment 

 of the nozzles almost complete protection has been afforded to a 

 number of commercial vineyards. 



The apple and cherry ermine moths. — In Technical Bulletin 

 'No. 24 attention is called to the occurrence of these insects in the 

 United States and to their economic importance as fruit pests. 

 These insects were introduced in shipments of foreign nursery 

 stock and appeared in plantations of apple and cherry seedlings. 

 It is stated that since the insects were first detected in 1909 special 

 precautions have been taken by the agents of the Division of 



