RUST OF THE ORANGE RKMEDIES. 117 



Flowers of sulphur must therefore be regarded as one of the cheapest 

 and most effective remedies for Eust-mite, and it may be used to great 

 advantage in connection with whale oil soap or other insecticides. It 

 may be suspended in water and applied in spray. With proper ap])li 

 ances the dry powder may be silted or blown upon the foliage when 

 wet witli dew or rain. A little wheat flour added to the powder would 

 increase its adhesiveness. 



The pharmaceutical preparation known as milk of sulphur (precipi- 

 tated), although a much more finely divided powder, proves milder in 

 its effect upon the Mites, and its cost will prevent its extensive use. 



EXPERIMENTS. 



(1.) A 8>mall seedling Orange infested with Rust-mite was covered 

 with a nail-keg and fumigated for ten minutes by burning one ounce of 

 sulphur under the keg. All the Mites were destroyed, but the eggs 

 remained alive ten days, and finally dried up with the leaves of the 

 plant, which was entirely killed. 



(2.) Flowers of sulphur dusted over infested leaves through a loosely 

 woven cloth. Free Mites all dead in twenty-four houi-s. Molting 

 young all dead in three or four days. Eggs not killed in nine days, 

 but young Mites killed soon after hatching. 



(3.) Experiment No. 2 repeated in the opeu air, and leaves allowed 

 to remain on the tree. Heavy rains on the second day did not remove 

 all the sulphur. Results the same as in ]So. 2. Mites all killed. Eggs 

 not killed. 



(4.) Milk of sulphur dusted upon the leaves through muslin. Effect 

 less ])owertul than in Nos. 2 and 3, but Mites in the end all killed. 

 Eggs not killed. 



(5.) Milk of sulphur; two ounces, by measuie, of the powder suspended 

 in one gallon of water. Leaves dipped in the liquid, when dry were 

 lightly coated with grains of sulphur. Adult Mites dead on the second 

 day. Some molting Mites and numerous eggs alive on the second day. 



(6.) Leaf with Mites confined in a tight box with another leaf on which 

 8ul[)hur had been dusted. Ko effect after twenty-four hours. Un the 

 third day, however, only one adult Mite appeared to be alive. In six- 

 days all the Mites were plainly killed. Eggs not killed. 



This experiment was repeated with sulphur scattered in (he bottom 

 of the box, and precautions taken to prevent its contact with the Mites. 

 Results precisely the same as before. 



Xote. — By confinement in very tight metal boxes, Mites may be kept 

 alive between one and two weeks, «»r until the leaves dry up or mold. 

 The destruction of the Mites in this exi)erini('nt was therefore due <mi- 

 tirely to the slow volatilization of the suli)hur. 



(7.) Sulphuretted hydrogen. Leaves dipped in water strongly im- 

 pregnated with the gas. In twenty-four hours all adult Mites were 

 dead or dying. In thirty-six hours all free Mites were dead. In the 



