OX METHODS OF PREVENTING INSECT ATTACK 53 



The first protective step, which will greatly tend to diminish danger of 

 this nature, is to plant avenues with several different species of trees alter- 

 nating with one another. It is the pure avenues i.e., avenues consisting all 

 of one species which are liable to suffer most seriously from insect damage. 



I inspected a tun-tree avenue in Bengal some years ago. It was pure, 

 and there was scarcely a tree worth maintaining on the ground, so badly 

 had the crowns been attacked by the tun twig-borer (Hypsipyla). The 



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FlG. 27. Section of stem of a I>all'cr^ia sisst><> tree, showing the sapwood riddled and 

 destroyed by the wood-borers Siiio.\vlon crassnm, Lesne, and -V. nnalc. Changa Manga. 



crowns were thin and straggly, and afforded little shade, besides being 

 very unsightly, and the owner (the avenue \v;is on a tea plantation) had the 

 whole thing cut down and replanted. It is best, therefore, to avoid planting 

 pure avenues; but if such are desired, choose a tree which is not liable to be 

 attacked by some of the common insect pests. 



Fruit trees are often used in this manner with a view to obtaining a 

 yearly revenue from the fruit. These trees require watching just as they do 



