214 UNIVERSITY OF CALIFORNIA -EXPERIMENT STATION. 



In the case of staked vines it is possible to work this cage if the 

 top is left off, or enough of the top so as not to interfere with the 

 stake. An opening may be left in the top similar to the V-shaped 

 opening at the bottom. A staked vineyard was gone over with this 

 modified cage and practically no hoppers escaped through the opening 

 at the top. Such an apparatus can not be used at all, of course, on 

 trellised vines. For trellised vines we would suggest the use of sticky 

 shields as are used in New York vineyards, excepting that the canvas 

 be replaced by wire screen netting. These should be three or four feet 

 high and seven or eight feet long, and two of them operated together 

 on opposite sides of the trellis. 



FARM PRACTICES. 



Plowing. Plowing is sometimes done by California vineyardists 

 during the winter season for the purpose of destroying the grape leaf- 

 hoppers. This is partly based upon the supposition that the eggs 

 may be in the leaves or in the ground, or that the adult hoppers are 

 in some way killed in the operation. So far as having a direct effect 

 in destroying the hoppers is concerned, plowing is of little avail. The 

 only ones that will be killed are a few that may not be disturbed from 

 their resting places among the leaves, or otherwise accidentally buried 

 by the plow. During the cold or rainy days there may be a few thus 

 turned under, but ordinarily they are active enough to escape readily 

 before the plow. 



Plowing, however, may have an indirect effect on the hoppers by 

 depriving them of food, or of suitable sheltering places during un- 

 favorable weather conditions, and if this practice is generally carried 

 out in a neighborhood it will no doubt result in reducing the numbers 

 somewhat. However, a field may be free from hoppers during the 

 winter, but this is not necessarily an indication of freedom from spring 

 infestation. The insects are more generally distributed in the winter 

 season, but the bulk of them will usually be found in the vineyard, or 

 on the vegetation of the borders immediately surrounding it. They 

 may come in, therefore, from vineyards closely adjoining, so that 

 plowing a single vineyard may be of little help. When the plowing is 

 done in a single vineyard or over a small area it is likely to result 

 simply in driving them into other fields, where there is a better food 

 supply. Once in these other situations they may, or may not, come 

 back into the vineyard where they were originally. 



Sheeping. Some growers turn sheep into the vineyard soon after 

 the crop is harvested and allow them to eat off the leaves of the vines. 

 This should not be done until the leaves have completed their growth 



