INJURIOUS TO THE LEBBEK TREES OF CAIRO. 135 



soap, lime and water. At this time it was hoped that the trees treated in this 

 manner would throw out a fresh and clean growth and eventually again form 

 normal crowns. A new growth was put out, but in many cases it died back 

 before the autumn, as also did the main branches. The vitality of the trees 

 appeared to be exhausted. A considerable number of trees treated in the 

 above way retained their new shoots, but it seems rather doubtful whether 

 they will ever make good trees again. 



Drastic as this treatment was, there was little else to be done, since there 

 was no spraying apparatus available and the trees had reached a state when 

 the benefits of spraying would have been very uncertain. Moreover, spraying- 

 could only be carried on under considerable difficulties in Cairo, if at all. 

 The cutting back of the trees only anticipated by a few weeks the ultimate 

 result of the effects of attack by the mealy bug. 



The young lebbeks were cleared of isolated colonies of the pest by the use 

 of the paraffin_, soap and lime mixture applied with a stiff brush. This treat- 

 ment appeared to give satisfactory results. 



In a note sent to the town authorities dealing with the question of the 

 mealy bug, it was pointed out by the writer that in future it should be the 

 aim of those in charge of the trees to prevent the mealy bug from again 

 increasing to such numbers that the present drastic treatment should again 

 become necessary. 



This result could only be attained by improving the general health of the 

 trees and keeping a careful watch over them in order to note any tendency 

 on the part of the pest to increase. If it showed signs of unusual increase, 

 then only by spraying with an insecticide could they hope to keep it in check. 

 The insecticides recommended for trial were : paraffin emulsion, whale-oil 

 soap, and distillate oils. These suggestions were, of necessity, tentative, 

 since no previous work had been carried out in Egypt on these lines against 

 any insect, similar in its nature and habits to D. perniciosits, attacking city 

 shade-trees ; nor, for that matter, in other countries, so far as the writer is 

 aware. 



It should be our object to destroy the larvse and immature stages rather 

 than the adult females, since the latter are well protected by a waxy 

 covering. Moreover, as already pointed out, the colonies of females 

 frequently become so well protected with dead leaves and other debris, that 

 it would be difficult at this stage to reach them with a spray. Furthermore, 

 in order to affect the females and their ovisacs, it is necessary to employ a 

 penetrating wash, such as paraffin emulsion of 12-15 per cent. oil. Unfor- 

 tunately, this strength has a very serious effect on the foliage of the lebbek, 

 which appears to be particularly susceptible to burning by paraffin oil. The 

 scorching effect can be lessened to some extent by the addition of naphthaline 

 to the emulsion, but by no means entirely prevented. Even an emulsion 

 containing 6 per cent, oil burns the leaves, whether spraying is carried out 



