SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 15 



spiked and unsprayed trees in adjoining rows. It is not known 

 whether all the fruit was sold in the same market. The sprayed 

 fruit brought 98 cents per box, the unsprayed fruit 85 cents per bo.^. 

 The difference in price, though small, was twice the cost of spraying. 

 Because of the vagaries of the market, due to the daily fluctuation 

 in supply and demand, it can not be stated that the better grades 

 will always bring the better price, yet the data presented leave 

 no doubt that spraying raises the grade of the fruit and largely over- 

 comes the devitalized effect caused by insects, and that, other things 

 being equal, the better grades bring better prices. 



SPRAYING SCHEME FOR CONTROLLING CITRUS PESTS. 



As a general proposition the time to spray for the control of all 

 pests of citrus trees is when they are present in such numbers that, if 

 left to reproduce without artificial hindrance, they would soon become 

 injurious. In other words the pests should be killed before they can 

 do much damage to either the tree or the fruit. The pests should 

 always be kept in such a state of repression that they can do little 

 or no damage. In case the various pests of citrus are permitted to 

 become so abundant as to cause injury, the profits which may be ex- 

 pected from artificial treatment, such as spraying with an insecticide, 

 are, to a certain extent, lost. Fortunately the life history and habits 

 of nearly all citrus pests are such that good results can be obtained at 

 any time of the year when the spray is applied. Nevertheless there 

 are times when spraying is more opportune than at others. These 

 periods come when the largest number of the insects are very young, 

 for then they are killed most easily. 



The following spray scheme has been used very extensively for 

 four summers in Florida and generally has given satisfactory re- 

 sults. It must be admitted, however, that no hard and fast scheme 

 can be recommended, - and that to a large extent the number of 

 sprayings depends on the thoroughness of the work. 



I. Paraffin-oil emulsion; Government formula, 1-66 or 1 per cent 

 of oil. May. — The main object of spraying at this time is to kill 

 white flies, scale insects, and, to a large extent, rust mites. This 

 treatment, however, must not be relied upon to control rust mites. 

 The spraying should be done after the adults of the first brood of 

 white flies have disappeared and before the appearance of those of 

 the second brood. The fruit should be an inch or more in diameter. 

 Since this treatment is given before the beginning of the rainy season, 

 it does not interfere with the work of the beneficial fungi in reducing 

 those insects not killed by the spray. 



II. Lime-sulphur solution, 32° Baume, 1-50 to 1-75. June to 

 July. — The main object of this treatment is to kill rust mites, and the 



