2 BULLETIN 1117, U. S. DEPARTMENT OF AGRICULTURE. 



ous insects by entomogenoiis fiingi. It is favored by a rainy season, 

 more or less well defined, lasting from June to September, which 

 correlates reasonably well with the growing season of the trees. The 

 more important insect pests in a large measure are dependent upon 

 the new growth or " flush " of the citrus trees for their successful 

 development and reproduction. Hence the period of maximum 

 abundance of these insects, which naturally coincides with the period 

 of greatest food supply, at the same time coincides with the rainy 

 season. This is fortunate, for the environmental factors which are 

 normally present in the summer during periods of greatest insect 

 injury are very favorable for the development of the various species 

 of fungi that prey upon and destroy the injurious insects. 



These entomogenous fungi are worth millions of dollars to the 

 citrus industry. Owing to their excellent work, oranges and grape- 

 fruit are grown at a profit in many parts of the State where no 

 money whatsoever is spent on artificial remedial measures. It should 

 not be inferred that spraying to control citrus pests is not advised. A 

 greater profit can be enjoyed when sprays are employed judiciously, 

 particularly if they are utilized in a way to supplement the work of 

 the fungi, but citrus fruits can be grown at a profit in the absence 

 of any artificial measures, a condition probably not possible, for in- 

 stance, in the apple industry. The inestimable value of the entomo- 

 genous fungi to the citrus grower of Florida is thus evident. 



If it were possible to eliminate these organisms from the State 

 and at the same time permit the injurious insects which they attack 

 to remain uncontrolled by artificial measures, the growing of oranges 

 and grapefruit would be an extremely hazardous occupation in which 

 the monetary rewards would be negligible or absent. Other things 

 being equal, it is estimated that in the absence of these fungi the 

 annual citrus crop would be reduced by at least 50 per cent, so great 

 would be the injury wrought by scale insects and the white fly. 



These statements are based upon the experience of the Federal 

 agents, the State specialists, and the growers themselves, who, while 

 permitting other factors to function normally, have at times inad- 

 vertently or otherwise eliminated in small areas, by sprays of Bor- 

 deaux mixture, the entomogenous fungi, which are killed effectively 

 and completely by this fungicide. They have found that trees 

 sprayed with it afford excellent feeding places for the insect pests, 

 and that as the development and reproduction of the latter are unim- 

 peded by the entomogenous fungi, they multiply prolifically, caus- 

 ing heavy defoliation, a very high percentage of fruit drop, and 

 unsightly unmarketable fruit, and even threaten the very life of the 

 trees. 



