20 THE UNIVERSITY SCIENCE BULLETIN. 



be burned over in the winter, there vv^ill follow a great diminu- 

 tion of the hoppers the following season. Pastures especially 

 should be burned over once in two or three years if they are 

 seriously infested with these insects. The time of planting 

 certain crops, and the time of mowing grasses may be so regu- 

 lated as to result in escaping serious injury from the leaf hop- 

 pers. Thus Gibson reports that cutting the alfalfa crop from 

 a week to ten days earlier will often check the clover-leaf hop- 

 per. If a crop is mowed so as to catch most of the leaf hoppers 

 in the egg or nymphal stage the majority of the eggs will be 

 destroyed and most of the nymphs will starve before they can 

 migrate to other food. 



Hopperdozers are sometimes used as direct controls to catch 

 and destroy large numbers of the leaf hoppers when they are 

 present in unusual numbers. 



In the case of grain fields best results are obtained by plow- 

 ing as soon after harvest as possible and then keeping the 

 ground free from grass and weeds till planted. This, combined 

 with rotation and clean farming around the edges, would be 

 insurance against leaf-hopper da.mage. The beet-leaf hopper is 

 also controlled by cultural methods. 



The leaf hoppers in vineyards are mainly controlled by 

 spraying, though hopperdozers are sometimes used. The usual 

 spray material is "Black Leaf 40," 1 part to 1,500 or 1,600 parts 

 of water, applied at the time of the presence of the maximum 

 number of nymphs. Doctor Ball gives the same contact in- 

 secticide for the control of Empoasca mali on potatoes, using it 

 at the rate of one pint to 100 gallons of water with five pounds 

 of soap added, two applications to be made a week or ten days 

 apart. The rose-leaf hopper and forms doing similar damage 

 can be controlled in the same way. Mr. Childs suggests also 

 the use of the rose as a trap crop in the control of the latter 

 as an apple pest. 



At this point we may also call attention to another bad habit 

 of Empoasca mali. In Psyche, XXV, p. 101, 1918, Mr. George 

 Becker called attention to this species attacking man. The 

 writer has had several people tell him about being bitten by 

 little green leaf hoppers, but not till a short time ago did he 

 have any personal proof of the fact. One night, while collect- 

 ing under a light, he felt a little prick on his hand, and on look- 



