CONDITIONS LEADING TO DEMAND FOE SEAECH. 13 



this insect already prevalent in certain parts of Florida. As to the 

 comparative efficiency of these three methods authorities are not 

 universally agreed, but from an unbiased poiat of view it would 

 seem that each has its advantages over the others within certain 

 more or less restricted fields. A discussion of these restrictions is 

 unnecessary in this place. Suffice it to say that by 1909-10 results 

 of investigations had not established universally in the minds of 

 Florida orange orchardists the absolute commercial efficacy of 

 mechanical-control methods.^ 



CONDITIONS LEADING TO THE DEMAND FOR A SEARCH FOR 

 NATURAL ENEMIES OF THE CITRUS WHITE FLY. 



The climate of Florida is, in general, very damp, a condition 

 especially suitable to the free development of funfous diseases. 

 Six different fungi have been recorded as attacking the citrus white fly, 

 and their resultant destruction in localities of much humidity appears 

 at times to total a high percentage. 



Following a movement toward efficient organization of the citrus 

 industries of Florida, the extent of damage which results from white- 

 fly infestation, as well as its direct bearing on the market quality of 

 the fruit, was brought forward with renewed force. Considering 

 the failure at that time of the mechanical methods to meet ade- 

 quately the demands of the orchardists, coupled with the apparent 

 partial efficiency of fungous diseases, the time seemed ripe that the 

 popular idea of control by natural enemies should gain a devoted 

 following. 



This theory of control by natural enemies, in brief, is that all life 

 in its native home is kept in check by other forms of life which prey 

 upon it ; in other words, that all nature is in a state of equilibriiun. 

 Chief among these natural factors of control in the case of insect 

 pests are other forms of insect life which are parasitic and preda- 

 tory on the noxious form. In recent years much attention has 

 been devoted to the discovery and subsequent introduction from 

 one country into another of beneficial insects for utilization in 

 attempted control of certain of our more important insect pests. 

 One of the earliest importations into America was that of a small 

 lady-beetle, Novius cardinalis Muls. For several years a large scale 

 insect called the cottony cushion scale {leery a purchasi Mask.) had 

 been producing such extreme injury to the orange and lemon groves 

 of California that the industry was threatened with ruin. Mechani- 

 cal means of control proved ineffective. In the belief that the insect 

 had been introduced into the United States from Australia, Mr. 



1 Fumigation, though highly eflScient in itself as a factor in the control of the citrus white fly, has 

 not met with general adoption, largely because of certain practical considerations which render it 

 unavailable economically under present conditions in Florida. However, recent results with special 

 oil sprays have placed the control of the white fly on a very satisfactory commercial basis. 



