LOUISIANA CIRCULAR No. 4. 



33 



possible so that much of it will remain on until after the scale 

 insects commence breeding in the spring.* 



Application of lime-sulphur after the buds have commenced 

 to swell results in these being killed and the crop lost. As peach 

 buds, espcially in Southern Louisiana, frequently swell with a 

 warm period in February, the second spraying should be com- 

 pleted not later than February 10th. In orchards where there is 

 but a slight infestation, or where the scales have been brought 

 fully under control by two sprayings the previous winter and 

 have not increased to any great extent, one application only is 

 necessary and this should be made late in January or early in 

 February. Where one spraying is depended upon, special pains 

 should be taken to make it thorough. Although the lime-sulphur 

 is sure and certain death to fruit buds that are opening, abso- 

 lutely no danger to either buds or trees is incurred when the* 

 wash -is applied to thoroughly dormant trees. 



When the scale has once been brought under control by two 

 sprayings during one winter, subsequent control is usually in- 

 sured by one spraying a year, and where the work has been care- 

 fully done we have known orchards to go for two years after 

 spraying without requiring additional applications. In spite of 

 the fact that this preparation will keep the scale fully under con- 

 trol, will prevent injury to the trees by the scale and still permit 

 the production of more and better fruit than is possible in an 

 uninfested unsprayed orchard, the fruit-grower should not enter- 

 tain the hope than by this spraying he will entirely exterminate 

 the scale. Some few individuals always escape to ultimately re- 

 infest the orchard, and although we have seen several peach or- 

 chards in which not a single scale could be found for several 

 months after the spraying, we have yet to find an orchard in 

 which the pest was killed ' ' to stay killed. ' ' 



*The lime-sulphur wash is not immediately fatal to more than a small 

 per cent, of the scale-insects but, unlike most insecticides, its action is slow 

 and is continuous for several weeks after its application to the trees. A chem- 

 ical study of this mixture, made by J. K. Haywood (Journal Am. Chemical 

 Society, Vol. 27, pp. 244-255) showed the completed mixture to contain sulphur 

 as free sulphur and as calcium sulphites, sulphates and the thiosulphate. Upon 

 exposure to the atmospheric conditions after spraying, the thiosulphate gradually 

 decomposes, liberating finely divided sulphur and sulphites, the final result being 

 free sulphur and calcium sulphate. The finely divided mineral sulphur is thought 

 by the author quoted to be the effective agent in killing the scale-insects. 



