BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 385 



f 



Williams of Goleta has done a considerable amount of summer spraying 

 with a tobacco spray with very satisfactory results. The following 

 mixtures may be suggested for work of this sort. 1 In applying them a 

 special effort should be made to spray the under side of the leaves, as 

 this is where the insects are found. Spraying should be done as early 

 in the season as possible in order to exterminate the insects before they 

 multiply. It is hoped that systematic experiments along this line may 

 be made during the coming season. 



Soap Solution. 



Soap 1 pound. 



Water 5 to 15 gallons. 



Whale-oil or fish-oil soap preferable, but for small amounts any yel- 

 low laundry soap will answer. 



Tobacco Soap. 



Blackleaf 40 _ 1 pound (1-10 gallon). 



Cresol soap, 1 gallon or whale-oil soap 10 pounds. 



Water 200 gallons. 



The cresol soap requires no heating. 



BLISTER MITE ERINOSE. 



This is a very common trouble of the walnut tree but not a serious 

 one. Its effects are seen in the form of blister-like swellings or eleva- 

 tions on the leaf surface, which are convex on the upper and concave 

 on the lower side of the leaf. These swellings are caused by numerous, 

 very small insects which live within the blisters on the under side of 

 the leaf amongst a felt-like, hairy growth which develops there. While 

 this effect is very common, it produces no appreciable injury and needs 

 no treatment for its control. 



RED SPIDER. 



This is a very small mite which sometimes becomes extremely abun- 

 dant on walnut leaves, causing them to dry and even to fall from the 

 tree. The insect is not ordinarily serious except in very hot climates, to 

 which the walnut is not well adapted. In such situations red spider 

 usually hastens the dropping of the leaves caused by too intense sum- 

 mer heat. 



Circular 66, Cal. Agr. Expt. Sta. 



18231 



