BULLETIN 195. 



CALIFORNIA GRAPE ROOT-WORM. 



21 



moisture just below the mulch and encourage the larvae to come nearer 

 the surface to transform to the pupae. If then, at the proper time, 

 just before the beetles begin to emerge, the soil, about the vine is stirred 

 to a depth of about six inches, no doubt a large percentage of them 

 will be destroyed. Another point, and one which makes the problem 

 more difficult, is that the pupae do not all appear at once, but may be 

 found for a month or more. This may make it necessary to go over the 

 ground more than once. However, probably the majority of the beetles 

 emerge at about the same time in the early part of the season, and, if 

 measures are taken against the pupae just preceding the emergence, 

 large numbers of them will be destroyed. If more than one cultivation 



FIG. 16. Vines enclosed with mosquito netting to determine if beetles will emerge through 



uncultivated soil. 



is undertaken they should be done at intervals not to exceed two weeks, 

 since the pupae will complete their development within this period. 



This matter of deep cultivation for two or three feet around the 

 vine, while not expected to completely control the insect, will, never- 

 theless, aid in its control. It is, of course, of no use unless done 

 at the proper time when the insect is in the pupal stage. The 

 proper time for such cultivation during the past two years at Lodi 

 would have been during the last of April, but this may vary with the 

 season and locality. 



It is possible that in some soils the destruction of the beetles before 

 they emerge from the ground may be accomplished in another way. 

 In making some experiments at Florin, in 1905, for the determination 

 of the causes of the sunburn of Tokay grapes, Mr. B. J. Wingfield 



