78 



Many of the pupae may be destroyed by deep cultivation for a 

 radius of two or three feet about the base of the vine. The beetles 

 may be killed by a strong arsenical spray, or by jarring into crude 

 oil, or otherwise captured as they are shaken from the vine. (Bui. 

 195, Col. Agr. Exp. Sta.) 



The Grape Phylloxera. The phylloxera occurs normally in four 

 forms, which have been called by Victor Mayet: 1. The gall insect, 

 or form of multiplication ; 2. The root insect, or form of devastation ; 

 3. The winged insect, or form of colonization ; 4. The sexual insect, 

 or form of regeneration. 



The gall insect lives upon the leaves, and is the commonest 

 form on the wild vines in the native habitat of the insect. It rarely 

 or never occurs in California. In Europe it is found often upon 

 American and rarely upon European varieties. It causes little swell- 

 ings or galls upon the leaves and younger parts of the vine, which, 

 though sometimes very numerous, do little permanent injury. The 

 chief danger from the gall form is that it multiplies with astonishing 

 rapidity and migrates from the leaves to the soil. Here it attacks 

 the roots and gives rise to the root form, which is the form of devas- 

 tation, the one which finally destroys all the vines it attacks which 

 are non-resistant. Every insect of the root form which reaches 

 maturity lays about twenty-five or thirty eggs, each of \vhich is 

 capable of developing into a new egg-layer needing no fertilization. 

 As there are from five to seven such generations during the year the 

 increase in numbers is extremely rapid. 



The most satisfactory method of combating phylloxera is the use 

 of resistant vines, because it is applicable to all conditions and is the 

 most economical in the end. 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: 1st, that the insects 

 do not increase so rapidly on its roots; and, 2d, 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. 



Though high resistance to phylloxera is essential in a grafting 

 stock, there are other characteristics equally necessary. The Rotund- 

 ifolia (Scuppernong), which has the highest resistance of any vine, 

 is useless as a stock on account of the impossibility of grafting it with 

 any Vinifera variety. This is due to a lack of affinity, which means 

 a lack of similarity in structure and composition between the tissues 

 of the stock and those of the scion. This lack, in extreme cases, 

 results in an imperfect and temporary union, but when not excessive, 

 onjy a slight decrease of vigor. The affinity is not perfect between 

 Vinifera varieties and any resistant stock, but in the case of Riparia 

 and Rupestris is generally sufficient to insure permanence to the 

 union, and the slight decrease of vigor consequent often results in an 

 increase of fruitfulness. 



The Strawberry Root-Louse. Whenever numerous bare spots 

 are found in a strawberry bed, and the remaining plants are more 

 or less unhealthy, failing to mature fruit properly, the owner will do 



