72 INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



i:. Bla«k leaf 40 1 pound 



Cresol soap (liquid) 1 gallon 



Water 200 gallons 



This mixture is a very efficient spray and a coming favorite for 

 many pests because of this and its simplicity of preparation. The 

 spray tank is filled with water and the "black leaf 40" and liquid 

 cresol soap are added cold and only a brief agitation is necessary 

 before the material is ready to be applied. It is specially effective 

 against the woolly apple aphis or any cottony-covered plant louse 

 and even better for the unprotected species. 



Other sprays which may be used with fair success are carbolic 

 acid emulsion, resin wash and oil emulsions, but all of these are 

 improved by the addition of 1 part of black leaf 40 to 1000 parts 

 of the diluted sprays. 



Natural Enemies.— There are many iusects preying upon the soft- 

 bodied and almost wholly unprotected plant lice. The most common 

 predaceous ones belong to the three families, Coccinellidce (ladybird 

 beetles), Clirysopidce (green lacewings) and Syrphidce (syrphid flies). 

 Large numbers of other insects also prey upon the plant lice, but are 

 too numerous to mention here. 



Many minute hymenopterous parasites also work upon aphids and 

 the mummied bodies of the latter with circular holes in the backs are 

 evidences of their execution. Under the discussion of Hymenoptera 

 their efficiency and methods of work are more fully given. 



Fungous diseases kill many of the lice, especially during the early 

 spring, when there is much moisture. 



THE GRAPE PHYLLOXERA 



Pcritymhia vitifoliw (Fitch) 

 {Phylloxera vastatrix Planchon) 



Description.— The presence of this pest is usually manifested by 

 its work, which consists in the formation of rough, wart-like galls 

 upon the leaves and small knots upon the roots. The lice producing 

 the galls are very small and orange-colored. White eggs as well as 

 the young are also to be found within the galls which, however, are 

 seldom seen in California. 45 The root lice are about 1-25 inch long and 

 greenish-yellow in summer and a little darker in winter. 



Life History.— During the months of July and August some of 

 the eggs laid by the females of the root forms hatch into individuals 

 which acquire wings. These seek the foliage of the vines and lay 

 large eggs which produce true females, and small eggs which pro- 

 duce males. These sexes mate and each female lays a single winter 

 egg upon the bark of the two-year old wood. In the spring these 

 eggs hatch into a root form (or gall-making form) which produce 

 the root-feeding forms in other stages, which in turn lay eggs giving 

 rise to the many summer generations of devastating root aphids. In 



'«' Iworth, C. W. Cir. No. 102, Cal. Agrcl. Exp. Sta., 1913. 



"The gall stage on the leaves is sen. Tally omitted in the life history of this louse 

 lifornia. 



