BULLETIN 195. CALIFORNIA GRAPE ROOT-WORM. 23 



The effectiveness of a method based on this experiment would depend 

 largely on the type of soil. Only a soil that will form a hard, com- 

 pact surface layer could be utilized according to this plan. 



We do not know how it would appeal to the growers to leave three 

 or four feet about the vine uncultivated until about the middle of May 

 or possibly later, as would be necessary in this case ; but if the beetles 

 were present in large numbers and this controlled them, it would pay 

 amply. Again, showers of rain that are apt to come as late as the mid- 

 dle of May would soften the soil and militate against the method. 



Spraying. The adult or beetle eats away portions of the leaf or 

 gouges- out strips of the surface of the shoots and other growing parts, 

 so that a poison applied to the vine will be consumed by it in this opera- 

 tion. The most serious drawback to poisoning is the fact that beetles 

 are pretty resistant to poisons, and considerable amounts must be con- 

 sumed before the insects are killed. However, if a strong arsenical 

 spray is thoroughly applied at the beginning of the attack it will 

 prove to be fairly successful. 



In the experiments this season the beetles were killed in from two to 

 three days on leaves thoroughly sprayed with lead arsenate in the 

 ratio of five pounds to fifty gallons of water. One pound of paris 

 green to seventy-five gallons of water also gave good results. In the 

 case of paris green a few vines should be used as a test to determine 

 the maximum amount that is safe for the foliage, since there is danger 

 of burning if used too strong. 



It is not a very difficult matter to spray the short-pruned California 

 vine during the last of April or the first of May, and thorough work 1 

 can be done at this time. The spray should be applied mostly from 

 above, since it is on the upper surface of the leaves and shoots that most 

 of the feeding is done. 



Jarring. Since the beetle is very readily jarred from the vine, this 

 offers one of the most satisfactory means of controlling the insect. 

 Generally it is only those that are in a cup-shaped leaf, or in a grape 

 cluster, or in some part of the old wood, that will not be disturbed by 

 a reasonable jarring. 



This method has the advantage of killing the beetles directly, before 

 egg laying is commenced, which may not always be done by means of 

 the poison spray. The worst objection to the method is that the beetles 

 may keep emerging from the ground for three or four weeks, making 

 more than one treatment necessary. Fortunately, however, these 

 attacks are generally confined to a limited portion of the vineyard, so 

 that the problem is not so difficult as it would be were it necessary to 

 go over the entire area. 



