Bugs, Cicadas, Aphids, and Scale-insects 179 



hatched young of the root form moves about freely, but when it reaches 

 the egg-laying stage it becomes fixed. 



The chief injury to the vine is not sap-drinking, but the decaying or 

 "cancer" of the roots caused by the punctures and tubercle forming (Fig. 

 249). It usually takes two or three years for phylloxera to kill a vine, but 

 the results of the infestation are shown each season in the increasingly reduced 

 growth of the new wood and in the lessened bearing. Suspected vines 

 should be dug up and the rootlets carefully examined for tubercles and 

 the insects themselves. The remedies, unfortunately, are either expensive, 

 difficult, or severe. If a vineyard can be submerged for six weeks under 

 at least six inches of water, the insects will be killed (by suffocation). Car- 

 bon disulphide can be put into the soil among the roots by an injector at 

 a cost of from ten to twenty dollars an acre. " This method succeeds only 

 in rich, deep, loose soils and cannot be successfully used in soil containing 

 much clay or on dry rocky hillsides." Finally, most severe but most effec- 

 tive is the digging up of the whole of an infested vineyard and replanting 

 resistant vines. "A resistant vine is one which is capable of keeping alive 

 and growing even when phylloxera are living upon its roots. Its resistance 

 depends on two facts: first, that the insects do not increase so rapidly on 

 its roots; and second, that the swellings of diseased tissue caused by the 

 punctures of the insects do not extend deeper than the bark of the rootlets 

 and are sloughed off every year, leaving the roots as healthy as before. 

 The wild vines of the Mississippi States have evolved in company with the 

 phylloxera, and it is naturally among these that we find the most resistant 

 forms. No vine is thoroughly resistant in the sense that phylloxera will not 

 attack it at all; but on the most resistant the damage is so slight as to be 

 imperceptible. The European vine, Vitis vinijera L., is the most suscep- 

 tible of all, and all the grapes cultivated in California, with a few unimportant 

 exceptions, belong to this species." But the preferred French stocks can 

 be grafted on to resistant American roots and the vineyard made practically 

 immune. This is the method which has rehabilitated the French vine- 

 yards and is now rehabilitating the California ones. 



Another very important aphid pest of this country is the woolly 

 apple-aphis, called in England and in Europe the American blight. This 

 species, like the phylloxera, appears in different forms and lives both above 

 ground on the twigs and larger branches and underground on the roots. 

 It makes itself conspicuous and readily recognizable by the abundant fluffy 

 waxen "wool" which it secretes. Badly attacked trees have the bark of 

 their branches badly "cankered" and the roots covered with excrescences, 

 and may die. The injuries are almost always severe, and the pest is one 

 difficult to eradicate. If but few trees in an orchard are attacked, it is best 

 to dig them up and burn them. The bark can be thoroughly sprayed or 



