Plant Sanitation. 



508 



[December, 1911. 



Mr Marlatt says:— Place the above 

 ingredients in an iron vessel, which 

 is to be kept exclusively for this pur- 

 pose, and boil for 20 minutes or until 

 dissolved. To 40 or 50 gallons of water 

 a pint of this stock solution and 

 3 to 4 pounds of freshly- slaked lime 

 are added. This excess of lime not only 

 takes up any free arsenic, but by its 

 distribution on the foliage enables one 

 to determine how well the spraying has 

 been done. This formula has been 

 thoroughly tested and used now for 

 many years, and is fully as efficient as 

 any other arsenical and far cheaper. 

 Chemically it is arsenite of lime. The 

 soda is used to hasten the process and 

 to insure the combination of all the 

 arsenic with the lime. The greatest care 

 should be exercised in preparing the 

 stock mixture, and afterwards it should 

 be plainly labelled to prevent its being 

 mistaken for some other substance. The 

 only objection to its use is the necessity 

 of handling the poisons in its home 

 preparation. 



Insecticides for Sucking Insects. 



A great number of contact poisons are 

 being used in the island for destroying 

 the various scale insects. Among the 

 most promising are miscible oils, petro- 

 leum, kerosene emulsion, and lime-sul- 

 pbur wash. 



Many of the best emulsions have been 

 condemned because they were not made 

 exactly according to the formula. This 

 has been especially true of the crude 

 petroleum and kerosene emulsions. Not 

 enough attention has been paid to the 

 making of these emulsions. Often in 

 ordering the ingredients the specific- 

 ations are not clear, and as a consequence 

 the goods that arrived are not just 

 what were desired. Imperfect emulsions, 

 in which the oil separates again from 

 the water after being diluted, result 

 from the use of hard water and from 

 shortening the time required in mixing. 

 Rain water should be used in making 

 emulsions. 



Miscible Otls. 

 Miscible oils are concentrated solutions 

 of ingredients which have insecticidal 

 properties to which it is simply necessary 

 to add water to form the emulsion. 

 They are usually handled commercially 

 and have become one of the most 

 promising scale destroyers. A manu- 

 factured miscible oil is used by some of 

 the fruit growers with good results, 

 having proved itself to be one of the 

 best scale remedies that has yet been 

 tried. The large growers cannot use it, 

 however, as it is too expensive. Tests 

 made here show that a strength of 1 to 



25 not only destroys all the crawling 

 young and those bearing the first cover- 

 ing, but also a great number of females 

 with eggs. This emulsion has been used 

 with good results on orange and grape- 

 fruit. At a strength of 1 to 20 some 

 leaves dropped, but these were incrusted 

 with scale or from badly infested 

 branches. Home-made miscible oils were 

 experimented with during 1908, and a 

 number of formulas have been tried. 

 The most promising are those made 

 with crude petroleum and rosin oil. 

 These give very stable emulsions and 

 their destructive power is very high. 



Miscible oils have many advantages 

 over the kerosene and crude oil emulsions. 

 After the soap is once made no more 

 heat is required to make the stock 

 emulsion or the various dilutions of the 

 stock emulsion. Only one-third of the 

 soap is heated and the other two-thirds 

 is made up of kerosene and water. The 

 time required for making the soap is 

 about an hour. 



If properly made they should not 

 have any free oil on the surface when 

 mixed with water. Emulsions made 

 with kerosene do not require as much 

 attention as those made with the 

 heavier oils, such as rosin, paraffin, or 

 crude oil. 



On April 21, 1908, a number of experi- 

 ments were made with the formula 

 recommended in Bulletin 79 of the 

 Delaware Agricultural Experiment 

 Station. The trees were incrusted with 

 scale at that time, but by March, 1909, 

 they were absolutely free from scale. 

 The scale did not immediately drop, 

 but the trees have been cleaned by the 

 rains and do not appear as if they would 

 need spraying during the coming season. 

 No ill-effects from these sprayings can 

 be seen. The trees have had their usual 

 amount of new growth and blossoms. 



There is always a small percentage of 

 leaves that drop, but they are usually 

 the ones which have been covered with 

 scale and have become weakened by the 

 constant action of it. The loss of such 

 leaves is not detrimental, as it is better 

 that they be removed. Healthy , vigorous 

 leaves are not injured. Similar results 

 have been obtained with paraffiD and 

 crude oils. 



These sprays should be applied with a 

 nozzle that gives a very fine mist. The 

 oils are very penetrating, and for this 

 reason a smaller amount of emulsion is 

 needed than of the old kerosene emulsion 

 sprays. 



Before the stock emulsion is taken 

 from the barrel the whole mixture must 



