BULLETIN 195. CALIFORNIA GRAPE ROOT- WORM. 7 



near Lodi these beetles have been very numerous for two or three years, 

 and the owner estimated that his crop had been reduced from one third 

 to one half. These two instances are comparable with what has occurred 

 over a considerable area in the Eastern States on account of the presence 

 of the other species there. 



Our species has been observed in several vineyards, and doing consid- 

 erable damage in 1908 where they were not seen at all in 1907. This 

 may be partly accounted for through the excessive rain in the spring 

 of 1907 causing their temporary disappearance, but there is no doubt 

 that the insect is becoming more widely distributed. The station has 

 also received more inquiries about the insect than usual during the 

 season just passed. 



The attacks of this beetle have been credited with being the cause of 

 the sunburn of the Tokay grape. The theory of those who support 

 this view is that the gnawing of the beetles on the stalks, pedicels and 

 berries "poisons the sap" or injures the bunch mechanically, and thus 

 induces the drying and shriveling of the berries. 



The experiments and observations of Messrs. 0. Butler and B. J. 

 Wingfield, at Florin in 1905, indicate that the above-ground attacks 

 of the beetle have little or nothing to do with causing sunburn unless, 

 of course, there is more or less actual defoliation. Besides exposure, 

 sunburn seems to be due to several causes, tending to diminish the 

 vigor of the vine, and probably the underground attacks of the beetle 

 larvae are among the most serious of these weakening causes. 



The Soil It Infests. The typical soil in the Tokay grape section about 

 Lodi is a sandy loam. It is in such soil that the vineyards mentioned 

 above are located. In another vineyard, however, near Stockton, beetles 

 were present in considerable numbers in the black adobe soil character- 

 istic of that region. About Florin, where the soil is clayey, the insect is 

 also troublesome. 



Dr. Felt 1 in speaking of the eastern root-worm's preference for soil 

 says: "The depredations of this pest are much worse and usually first 

 apparent in light, sandy or poor soils, and in particular on gravelly 

 knolls. The insects seem to thrive under such conditions and a defi- 

 cient growth should lead to immediate investigation. Vines on rich 

 clay soils in our experience sustain comparatively little injury from this 

 pest, and this appears to be the case in Ohio. ' ' 



Preference for Varieties. With a view to determining whether 

 or not seme varieties are resistant to the attacks of the eastern species, 

 the Cornell Experiment Station secured roots of several types of Ameri- 

 can vines, and after grafting them on to the standard varieties grown 

 there, distributed them in the infested districts. The work is still in 

 the experimental stage, but it may be promising as a line of possible 



1 New York State Museum Bulletin 59. 



