DISEASES OF CITRUS TREES ] 73 



the grubs should be collected daily, in order to give no 

 time to the grubs to hide within the ground, and it 

 should be disposed of in a manner so as to destroy the 

 grubs effectually. The rotten fruit may be collected in 

 a heap, sprinkled with petroleum and burned ; or it may 

 be thrown into a ditch or other reservoir and covered 

 with water, taking care to raise the water well over 

 the uppermost layer of fruit, otherwise the grubs will 

 get to this layer and undergo their metamorphosis. It 

 is also recommended to bury the rotten fruit in a deep 

 ditch covering each layer with quicklime, taking care not 

 to bury any fruit within 30 c.m. from the surface of the 

 ground. After six months the ditch may be opened and 

 the rotten fruit will be found to make an excellent 

 compost for the orange grove. There is little doubt 

 that if these preventive measures were widely adopted, 

 in a few years the havoc caused by the fruit-fly will 

 be greatly reduced. 



The pupae hiding in the ground are brought to the 

 surface by frequent tillage and are then picked up by 

 birds or destroyed more effectually by cold weather. 

 Oranges still hanging on the tree in April can be pro- 

 tected by enclosing them in small bags of cheap cloth, 

 taking care that the bag is wide enough not to close 

 tight upon the fruit, otherwise the fly may reach it 

 with its ovipositor through the meshes of the cloth. By 

 this means many an orange grower is permitted to keep 

 a certain number of oranges well into the summer, when 

 they will realize very good prices, and the same bag 

 if well cared for may be utilized for several years in 

 succession. For oranges as well as for other fruits paper 

 bags are often used, but these are liable to cause burns 

 on the fruit, and though cheaper are of short duration. 



The Hemiptera include a large number of parasites 

 of Citrus trees, most of them remarkable for their prodi- 

 gious power of increase. One of the Hemiptera, Sipho- 

 nopkora citrifolii or Toxoptera Aurantii is the Orange- 



