THE MONTHLY BULLETIN. 



49 



leaves are damaged to some degree, the main source of injury is due 

 to the attacks upon the young and vigorous roots which are completely 

 destroyed. The roots of the so-called "resistant stock" do not mate- 

 rially suffer from such attacks. 



Control. — By far the most impoi'taut method of control is the use 

 of resistant root stocks ui)on which are grafted the desired varieties. 

 Of course care must be exercised in selecting stock for the various 

 varieties and expert advice obtained before making extensive selec- 

 tions or plantings. 



Dirct remedies for infestations are unsatisfactory. Flooding the 

 vineyards if the water can be held for a month will almost exterminate 

 the pest, if done in the winter, but such a method is impracticable in 

 most of the grape-groAving sections of the State. 



Carbon bisulfid is an efficient remedy in loose sandy soil, but in such 

 places the pest is usually less abundant. 



Natural Enemies. — In the eastern states nuiny predaceous insects 

 feed upon the gall form, ])ut as this stage does not occur to any extent 

 in California there are practically no results from these or other nat- 

 ural cheeks. 



THE WOOLLY APPLE APHIS. 



Eriosoiiiu l<ini(jcra (Hausm. ). 



{Scliizoneura hiiiigcra Hausm.) 



(Figs. 39, 40, 41.) 



General Appearance. — To the average orchardists this insect is of 

 too connnon occurrence to need any suggestions to recognize it. The 

 dark red or purplish louse covered with the long white cottony wax 

 or flocculence is the most serious apple pest in many of the northern 

 comities. The winged forms are distinguishable by their dusky pro- 

 truding wings. The fall and early winter lice are dark yellowish or 

 brown in color. 



Life History. — In the summer, especially during the months of July 

 and August, the woolly aphis is. exceedingly abundant upon the limbs 

 of the trees, covering large patches with their extensive colonies. 

 Towards winter they gradually disappear, only a few individuals 

 remaining hidden under protecting bark or in crevices. In the 

 fall the winged viviparous females give birth to true males and females 

 which mate, each female laying a large egg which hatches into an 

 over-wintering form. These have very little cottony covering and 

 appear to be able to stand severe weather. The diminishing of the 

 aerial forms usually accompanies the increasing of those working 

 under ground upon the roots around the bases of the tree trunks. 

 Here they may be fomid in great numbers during the winter and also 

 during the early spring and even the summer months. These root 



4— II 



