30 REPOET OF SEARCH FOR ENEMIES OF CITRUS WHITE FLY. 



Europeans require hea-^^^ protection in order to withstand it. Then 

 frequently hot blasting winds blow with great violence, stkring up 

 the dust in dense clouds and rendering life doubly uncomfortable. 



In the direct rays of the sun the temperature during this time 

 often exceeds 150° F. Failing rains cause vegetation to dry 

 up and insects develop with difficulty. The following instance shows 

 the effect of drought on the white fly: 



In the Government Horticultural Garden at Lahore there is a very 

 large nursery containing smaU orange and lemon trees. These trees 

 were free of living Aleyrodes with the following exceptions: At 

 one side of the nursery there was a large, densely foliated deciduous 

 tree which overshadowed a number of orange trees. Some of 

 these trees which v/ere more densely shaded contained a small number 

 of living white flies. Near the center of the nursery was a densely 

 foliated tree about 10 feet tall, against the base of which were two or, 

 three small orange trees which were in shade throughout the day. 

 These trees contained some living white flies, whereas other trees 

 immediately surrounding but exposed to the sunshine contained 

 none. Moreover, it can be stated that at no place in India did the 

 writer find living Aleyrodes on small nursery trees except in situa- 

 tions that were weU protected by shade. 



The most severe and at the same time extensive infestation of the 

 white fly on citrus in India occurred on a large hedge at Lahore, and 

 this was utilized in the writer's breeding and collecting work. A 

 part of this hedge was protected by a cloth awning and this protected 

 portion was infested on aU parts. (See PI. VIII.) On the part not 

 covered with awning the white fly occurred in abundance only where 

 the hedge was protected by densely foliated overhanging trees which 

 kept the direct rays of sunlight from the hedge plants throughout 

 the heat of the day. The side of the unprotected hedge exposed to 

 the direct rays of the afternoon sun was entirely free of living white 

 flies, whereas on the lower part of the opposite side, which was in 

 shade except for a very short period in early morning, living flies 

 could be found in considerable numbers. 



In the case of large citrus trees the gi^eatest number of living 

 insects was invariably found in those having the densest foHage. A 

 tree in which the foliage was light seldom contained living fhes 

 except where protected by the shade of a large overhanging species. 

 Although the white flies appeared to prefer trees of the tangerine 

 variety, they were seldom able to multiply to any extent on these 

 because of the small leaves and the less dense foliage than that of 

 other varieties. In any species of citrus in which living specimens of 

 the white fly occurred the infestation was found almost invariably in the 

 shadiest part of the tree or the interior part near the mam branches. 



