66 
Indian Forest Records. 
[Vol. VII. 
Economic Importance. 
The economic importance of the pest may be considered from two 
standpoints: (a) injury to the seed-crop, and (b) injury to the growth 
of the tree. 
(a) Injury to the seed-crop. —The consumption of the flowers and 
fruits by the first two generations amounts, in bad years, to a com¬ 
plete destruction of the seed-crop. Past records from the Punjab and 
Bengal indicate that difficulty is occasionally met with in collecting 
sufficient sound toon trees for sowings. In Australia heavy seed-crops 
of Cedrela australis have been almost completely ruined by a borer, 
which is beyond doubt Hypsipyla robusta (Queensland Forestry 
Bulletin, No. Pt. I, 1917, p. 14). 
(b) Injury to the Growth of the Tree. —This type of injury, being 
more obvious than the first, has been more frequently recorded in litera¬ 
ture and departmental reports. (See Previous History of the Pest). 
The combined work of the third, fourth, and fifth generations on 
young toon trees completely nullifies the season’s growth ; not only 
are the main leaders of the current year killed, but also laterals which 
have made progress on the woody stems of the previous years. The 
growth of the sapling appears to be completely checked, but, in the 
course of time, occasional shoots escape attack and become lignified 
before the succeeding season and some upward progress is made. In 
its early stages, the attack of the borer is characterized by a dense 
bushy growth (See Plates XI, XII), and, in its later stages, by much 
branched bole and crown, the bifurcation of the main branches always 
occurring low down on the trunk*. (Plate XIII shows the character¬ 
istic branch development of old toon trees in an avenue subject to 
repeated attacks of the borer). 
Numerous records have been obtained in India to show that the 
establishment of young toon in plantations or in restocking of blanks 
is impossible in the proximity of old toon trees. The same difficulty 
arises with mahogany and, as already quoted, in other parts of the 
world with various species of “ Cedar 
* Incidentally, the presence of the borer may be considered an advantage in avenue 
prod iction, provided one is prepared to wait long enough. 
[ 2H 1 
