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INTERNATIONAL CONGRESS OF VITICULTURE 



Origin and Food Plants. 



The grape root-worm is an American insect and, no doubt, its original 

 food plants were the various species of wild grapes indigenous to its range. 

 It frequently feeds on wild species at the present time but shows a decided 

 preference for the Concord variety of cultivated grapes. Although no variety 

 has been found that is entirely immune to its ravages, Clinton and Delaware 

 grapes do not appear to be attractive to the beetle. The writer has never 

 seen a vineyard of either variety seriously infested by this insect notwith- 

 standing the fact that such vineyards were adjoining or even surrounded by 

 Concord vineyards having the root-worm present in considerable numbers. 



The question of the degree of immunity of varieties is one of both 

 theoretical and practical interest and here an interesting field awaits in- 

 vestigation. Inasmuch as the control of the grape root-worm is combined 

 with spraying for other insects and fungus diseases it is doubtful whether it 

 would pay to graft Concords on stock which is largely immune to the attacks 

 of this insect. If this would produce other advantages, such as increased 

 vigor, then grafting of roots might prove practical. 



Character and Extent of Injury. 



The adult beetles feed on the leaves of grapes eating chain-like areas on 

 the upper surfaces. The insect grasps a portion of the leaf with its 

 mandibles and then lifts its head thus tearing the tissue which it proceeds 

 to devour. A slight advance is made and another portion of the leaf is torn 



Fig. 1. Effect on leaf of feeding adults (slightly reduced). 



