REPORT OP COMMITTEE ON PUBLICATION 197 



per acre. It is necessary to include two seasons' crops in this estimate 

 for these insects usually injure the quality the first season but the effect 

 on the quantity does not appear until the second season. Only two serious 

 outbreaks have occurred in Chautauqua County, New York. And each 

 of these extended over but a few seasons. For this reason the average 

 annual loss is rather small. In other sections of the state, the annual 

 losses from this pest are greater because the outbreaks appear to occur 

 at more frequent intervals. The reasons for this latter condition are: (I) 

 the environment is favorable for hibernating; (2) in some sections, vine- 

 yards are grown in proximity to raspberry plantings which we have 

 learned affords the leaf-hoppers both suitable hibernating quarters and 

 (more important) food before the leaves of the grape appear. 



Factors Favoring Injury to Vineyards. 



A study of the ecology of this insect has revealed the reasons for the 

 variation in infestation found in a locality during the same season and may 

 explain the causes for the greater infestation found in certain regions. The 

 most severe infestation of vineyards have always been found where they 

 adjoined land having favorable conditions for hibernation of the leaf- 

 hopper or spring food plants of which raspberry and blackberry plantings 

 seem to be preferred. The locations favorable for winter quarters are 

 dead grass, that has lodged, and leaves, especially those of deciduous trees 

 which are resistant to moisture and to becoming tightly packed by snow. 

 For this reason fences, brush land, waste places grown up with grass, hay 

 fields, when the second crop has been allowed to lodge, and other places 

 in which such rubbish might gather were always found to shelter many 

 of the hibernating adults. During the warm days of autumn myriads of 

 leaf-hoppers fly about and travel short distances alighting in every place 

 they chance to find. Should they find conditions for winter quarters unsuit- 

 able they leave them and drift about until suitable places are found. The 

 first warm days of spring cause them to leave their winter quarters and 

 seek food. We again find them on the wing at times and as soon as rasp- 

 berries are found begin feeding on these. However all leaf-hoppers do not 

 migrate to berry leaves but many continue to feed on grass and weeds 

 which may be present, migrating to the grape leaves as soon as these have 

 grown to be an inch or two in diameter. Weedy vineyards also make 

 excellent places for these insects. Plants which remain green during the 

 winter, such as the several cover crops, do not shelter these pests to any 

 extent although a few of the insects may remain and feed on them. Plant- 

 ings which are sown to cover crops, which remain green during the winter, 

 or which are kept free from weeds and rubbish and have clear surroundings 

 are not severely attacked by these bugs. The practice of clean culture 

 has given the eastern vineyardists a powerful weapon of defense against 

 the enemy. The writer studied the distribution of these insects in Chau- 

 tauqua County during the severe infestation of 1912 and at that time few 

 infested vineyards were found on the heavier soils. All observations indi- 

 cate that either the leaf-hopper seeks dry situations in which to hibernate 

 or the individuals which go into winter quarters on the lower soils die 

 through flooding of these places or on account of the continual dampness. 



