IS 



less injury resulted to the foliage when the operations were performed 

 at night than when they were carried on in sun-light. It is said that 

 chemical changes are produced in the gas by the action of sun-light 

 and that the resulting gases are more injurious to the plant life 

 and less to animal than hydrocyanic acid gas. Whether or not these 

 theories are correct is of small practical importance, for the foliage of 

 a tree will suffer serious injury if the tree is left covered with an air- 

 tight oiled tent for half an hour in sun-light, without the gas being 

 present. Having ascertained this fact, by experience, the foreman in 

 charge of the Board's outfit refrained from covering trees until the 

 sun had sunk from sight on any but cool, dull days. The great majority 

 of the trees treated have been fumigated after sunset. The ideal 

 night for fumigating is quiet, cool, and moon-light, and without dew. 



Season for Fumigating. The operations may be successfully 

 conducted against the Red and Brown Scales at any season of the 

 year. The chances for thoroughly effectual work are best, perhaps, 

 during the latter part of February and March, when young insects are 

 most abundant. The operations of the Board began late in August 

 and have continued through to June without intermission save for the 

 first six weeks of the year, when work was suspended owing to the 

 non-arrival of supplies of cyanide, and during this period the treat- 

 ment has been uniformly successful. 



Injuries to the Tree.- -Injury to the tips of new growth gener- 

 ally results. This injury is in no wise serious and is quickly out- 

 grown. The operators consider it a favourable indication, as when 

 such injury results it is quite certain that the gas has been present in 

 sufficient strength to destroy all of the insects. When no " burn- 

 ing " results, there is always the suspicion that not enough cyanide 

 was used. 



The blossoms appear to be less affected than the foliage and very 

 little damage is caused to them. The fruit, likewise, is not sensitive 

 but a little generally drops after a few days ; this dropping may be 

 due, in part at least, to mechanical injury in raising and lowering the 

 cloth. 



If a heavy overdose is administered, all of the foliage and fruit 

 may fall and the young wood die back. Very small trees are most 

 likely to receive an overdose ; and unless trees under four feet in 

 height by three in diameter are badly infested with scale insects, it 

 is best not to risk injuring them. Any excess given to a tree of even 

 this size will cause as much damage as seven times the same excess 

 given to a tree of double the dimensions. These remarks apply only 

 when the trees are treated singly, not when a number are treated 

 under the one tent, as can be safely done in nursery rows. If many 

 small trees are to be treated, a frame to keep the tent expanded to 

 encompass a space for which a dose can be safely administered, had 

 best be used. 



