FORTIETH ANNUAL REPORT. 139 



cation will kill iusectn; insects Avliich do not have chewing mouth parts. 



The fii'st two are the ones which I wish to consider at tJiis timle. 



It has long' been tlie practice to use Bordeaux for summer spraying 

 of fruit, and in combination with this to use some form of an arsenical 

 ]:oison for the purpose of killing insects which alfect the trees during the 

 summer. The arsenical poisons which are used are Paris Green and Ar- 

 senate of Lead. Arsenate of Lead sticks to the foliage better and does 

 not have the burning effect which is so characteristic of Paris Green. 



In combining arsenical poisons Avith lime sulphur sprays, there is one 

 l>oint which must be considered. There are various forms of arsenical 

 poison. One of them is arsenate of lead and another is Paris Green and 

 another is arsenate of soda and another is what is known as ''Kedzie 

 Mixture." The essential (juality necessary is that the arsenic must be 

 in an insoluble form and this one requirement alone will disqualify both 

 arsenate of soda and ''Kedzie mixture." Hence these two forms must 

 not be used. The reason for insolubility is simply this, when combined 

 with sul}>hur. a soluble arsenical comj)ound will react chemically with 

 the sulphur, forming sulfide of arsenic, which is a heavy precipitate. 

 Evidence at hand today goes to show that this reaction destroys both the 

 fungicidal and insecticidal action of the spray, for sulfide of arsenic is 

 not known to be either an insecticide or a fungicide. Hence either Paris 

 (7reen or Arsenate of Lead must be used in connection with lime-sulpliur, 

 if insects are to be attacked. I wish to call attention to the advantage 

 of such a lime-sulphur spray over Bordeaux for summer spraying of 

 apples. 



The exhibit at the college which we have here shows the difference in 

 the effect of russeting by Bordeaux and by lime-suli>hur summer sprays 

 which you have all seen. I therefore wish to bring out this point that 

 for a summer spray instead of the Bordeaux, a weak lime-sulphur solu- 

 tion is very much more advisable. And with the lime-sulphur may be 

 combined an arsenical poison for the pur^wse of combating insects the 

 same as with Bordeaux. You have seen the exhibit and have doubtless 

 noticed how much more marked was the russeting of the fruit when 

 sprayed with the Bordeaux than when the lime-sulpiiur spray was used. 

 So in closing, I wish to leave with you two points. First— that a weak 

 lime-sulphur spray made according to the ordinary formula and applied 

 as a summer spray will not produce anything near like the russeting 

 effect on the fruit as will Bordeaux and second — that this lime sulphur 

 may be combined very successfully with an arsenical poison for destruc- 

 tion of insects. 



