THE WALNUT — ENEMIES. 37 



tLTi^^ ^^IV^^'^P *^® ^^^^- ^^^ ^^'^^a cannot easily be discovered, for 

 W ^f^^°^.*^at the trees do not begin to show the effects until the larva 

 fppLv rpV'^? *° develop to its full size, when it becomes a voracious 

 tw T . ^^^"^^ remains in that state three days, and changes to the 

 cnrysaiis state about the month of June, as the beetles generally make 

 tHeir appearance in July. •= •' , 



Remedy. —It is very difficult to ascertain the presence of borers before 

 ine trees indicate their presence. Walnut trees sometimes are observed 

 to oe bleeding (oozing sap) from a certain spot; this indicates a borer, 

 or navmg been damaged otherwise. However, the cause should be 



Fig. 7. 



carefully looked into by cutting into the bark, and the borer destroyed. 

 The wound should then be covered over with such material that will 

 prevent the action of the atmosphere from injuring the tree. 



SPAN WOEM. 



In 1891 there appeared in this State, at Santa Barbara, a caterpillar 

 commonly known as the "span worm," infesting the walnut in great 

 numbers, and in some places the trees were almost completely defoliated. 

 The insect is easily subdued by the following remedy: Paris green, 1 

 pound; water, 200 gallons. The remedy is applied as soon as the cater- 

 pillars make their appearance in the spring. 



WALNUT APHIS. 



This insect attacks the walnut in some sections, and its exudations 

 form on the tree a sort of "honey dew," which forms into a fungus and 

 renders the foliage and husks quite black. 



The black Australian ladybugs, Rhizobius ventralis, Rhizobius debelis, 

 and Rhizobius Toowoombm, have kept this insect in check, through which 

 agencies the injury is not felt. 



WALNUT BACTEBIOSIS. 



The only known disease, aside from " root knot," reported as attack- 

 ing the walnut, which has caused some alarm, is a species of fungi. 



*"It is not inown as yet whether the primary cause of the trouble is due to some 

 derangement of the vital functions of the plant. or to parasitic organisms. The progress 

 and destructive action of the disease are certainly very apparent. A small black spot 

 first appears on the side of the nut husk while the kernel is still in the milk. The death 

 of tissue beneath this spot gradually extends, spreading inward, and soon reaches the 

 shell. Unless the shell is already hard the decay penetrates through the soft meat of 

 the nut within, and the whole is soon disorganized and turns black. * * * A study 



*Keport of Division of Vegetable Pathology, Department of Agriculture, 1893, p. 272. 



