REPORT OP COMMITTEE ON PUBLICATION 199 



former being found after June 15th. The females die during the latter 

 part of June and July. 



A second-brood of leaf-hoppers is produced during hot, dry seasons 

 and usually a partial second brood during a normal season. Eggs are laid 

 by the earliest developing adults during August and perhaps September 

 for young nymphs of the first instar have been found as late as October 

 1st. Most of the nymphs of this brood develop into adults during late 

 September and early October but it is believed that many of the nymphs 

 never develop into adults owing to their late appearance unless they reach 

 maturity on other plants. Nymphs have never been observed hibernating. 



The length of life of the single brood insect is about one year but the 

 length of life of the adults during years having a second brood has not 

 been determined. 



Natural Control. 



All entomologists who have studied this insect have noted great reduc- 

 tions in the number of leaf-hoppers infesting vineyards but the exact causes 

 of these diminutions in numbers are not known. Climatic conditions 

 appear, however, to be an important factor. 



The serious outbreak of 1911 and 1912 terminated rather suddenly 

 during the late summer of the latter year and abnormal weather low 

 temperatures and excess of rain is believed to have been the cause. The 

 nymphs did not seem to thrive so that few reached maturity. A worker 

 has reported that high temperatures kill the insect but this has not been 

 the cause in New York vineyards. 



Predaceous and parasitic enemies exact their toll but careful observa- 

 tions indicate that these play only a small part in the reduction of the pest. 

 After a study of the literature and personal observations made during a 

 period of decided decrease, the writer must acknowledge that we are 

 ignorant of causes of natural control of these insects. 



Remedial Measures. 



Under conditions obtaining in the northeastern United States it ap- 

 pears that several methods of control are practical. The following have 

 been noted or used by the writer: (1) destruction of hibernating places 

 either by clean culture during the summer or by burning over such places 

 during the fall or winter; (2) avoiding the planting of bush fruits close to 

 vineyards; (3) the allowing of the shoots or "suckers" to remain at the 

 base of the vines until early July; (4) spraying with nicotine mixture to 

 kill the nymphs. 



Destruction of hibernating quarters. Any practice which will keep 

 vineyards and especially the land surrounding the same clear of weeds 

 and grass will prevent the leaf-hopper from hibernating near the vines and 

 this has been found to keep the vineyards free from serious infestation. 

 If the surroundings have grown up to grass which has died and lodged 

 especially if leaves have been gathered here by the wind, the most practi- 

 cal measure usually is to spray these with kerosene if they will not burn 

 readily and destroy these refuges by means of fire. This method was used 

 by several grape growers with success during the 1911-1912 infestation. 



