GRAPE INSECTS 451 



The California Grape Root-worm 

 Adoxus ohscurus Linnaeus 



In California the grape is attacked by a beetle which, in 

 habits, life history and the nature of the injury inflicted, is very 

 similar to the grape root-worm of the Eastern states. This 

 beetle has a wide distribution in Europe, Siberia, northern 

 Africa and the northern part of North America. It has long 

 been recognized as a pest of the grape in France, Germany, 

 Italy and Algeria, but in this country it has attracted attention 

 only in California, although it is known to occur from New 

 Hampshire to the Pacific through the Northern states and 

 Canada. There are two forms of the beetle, a black and a 

 brown race ; in Europe only the brown form is known to attack 

 the grape, but in California both forms are found on the vine 

 and interbreed indiscriminately. The original wild food-plants 

 both in this country and Europe are the various species of 

 Epilobium or fire-weed. 



The majority of the beetles emerge from the ground in the 

 first half of May, and practically all disappear by the last of 

 June. The beetles are about -^ of an inch in length. There 

 are two color varieties : one is almost entirely black ; in the other 

 the head and thorax are black, the wing-covers brown. Both 

 varieties are clothed with a short gray pubescence. The beetles 

 feed on the upper surface of the leaves, eating out chain-like holes 

 or grooves ; they also attack the tender shoots, and the petioles 

 of the leaves, the fruit stems and even the small berries. 



After feeding about two weeks the female begins egg-laying. 

 The yellowish-white elongate eggs are deposited in clusters 

 of ten to thirty in crevices beneath the strips of loose bark on 

 the old wood. They hatch in 8 to 12 days, and the young 

 grubs soon reach the ground and burrow down to the roots. 

 They first feed on the smaller roots, but later attack the larger 

 roots, eating longitudinal furrows in the bark. Some of the 



