THE OLIVE IN ITALY. 657 



street at Kew Orleans is also another dangerous insect to the precious 

 plant. The same shown enlarged in Fig. 33 is destroyed with lye of 

 liine. 



FIG. 33. 



The Psylla, when in the state of larva, encircles itself in a sticky 

 whitish matter, and causes the plant to droop. 



This disease is generally called here malattia del cottone (cotton dis- 

 ease), and the most energetic remedy is to treat the plant by cutting oft 

 all the infected branches. 



Finally, the Cossoperdilegno (Oossuslegniperda) is the most terrible in- 

 sect, damaging the wood. Thecossuswheninagrubstateisbloodish-red 

 on top and white-yellowish under. The butterfly deposits an egg in the 

 bark, wherefrom grows a grub, which bores into the tree into the heart 

 of the tree killing it at once; if the tree is young, the cossus is assisted 

 in its work of destruction by a special liquor of a strong odor secreted 

 by the insect itself, which softens the wood fiber. This terrible insect is 

 difficult to be destroyed. It lives three years in a state of larva, and 

 the butterfly is found in the spring" and summer; consequently at such 

 a time it is necessary to use a certain activity to destroy it. The nat- 

 uralist Professor Boisduval advised the municipal authorities of the 

 infected places to " offer one lira of reward for every cossus caught as 

 a good remedy to destroy the same." 



Diseases. Besides the said insects there are also diseases to which the 

 olive plant is subject, such as (1) II Chiodo o Rogna (the nail or scab) 

 the cause of which is by some growers attributed to insect punctures, and 

 by others to the imperfect ass ; miliation of the juices, which instead of 

 alimenting the plant, accumulate at certain points, producing deformed 

 excrescences, as in Fig. 34, , a, a, a. 



H Chiodo (nail) generally dilates in olive groves propagated by ovoli 

 (springs), and greatly prevails where the forced method of propagation 

 has been practiced. The extravasation may be caused by wounds pro- 

 duced by hail, or by the bark cracking while the plants are inactive 

 vegetation, or by the ill-treatment to the bark while gathering the crop. 

 The cause most common, however, is excessive pruning. 



