REMOVAL OF SPRAY RESIDUE FROM APPLES AND PEARS 6 



efficient equipment. Dry cleaning is not generally facilitated by the 

 use of combined lead-arsenate oil sprays. In some districts, however, 

 through the use of oil the quantity of lead arsenate may be reduced 

 sufficiently so that the arsenic of the residue on the fruit at harvest 

 time will be below the required tolerance. 



Definite recommendations can not be made at this time for the use 

 of either hydrated lime or Bordeaux mixture in the sprays to facili- 

 tate the removal of residue at harvest time. There is a possibility, 

 however, that the addition of 1 or 2 pounds of hydrated lime to 

 each 100 gallons of spray in the last two spray applications will 

 facilitate residue removal and may reduce the arsenical calyx injury 

 that often occurs in some fruit districts owing to the formation of 

 water-soluble arsenic on the fruit after the early fall rains. 



It is assumed that in such cases the solvent used in the washing 

 treatment will be hydrochloric acid, because it is questionable whether 

 any other solvent than acid will remove the residue more effectively 

 when lime or Bordeaux mixture have been used in combination 

 sprays. 



When commercial fruit-cleaning plans were first made, the opinion 

 was that a grower could determine his cleaning procedure from the 

 number of cover sprays applied to the fruit. Experience has shown 

 that this is not possible, except in a very general way. Examination 

 of the fruit by chemical means offers the only reliable basis for 

 determining whether fruit sprayed with arsenicals requires cleaning 

 to meet any tolerance that may be in force. 



The maturhVy of the fruit has a marked influence upon the facility 

 with which it can be cleaned by any method. The development of 

 waxy or oily materials on the surface of the fruit which may make 

 satisfactory cleaning difficult apparently takes place throughout the 

 growing season, but it becomes very noticeable particularly after 

 harvest on some varieties of apples, such as Winesap and Arkansas 

 Black, as the fruit approaches a ripe condition. As the maturing 

 fruit becomes softer it is also more subject to injury by mechanical 

 means and provides a greater possibility for decay development. 

 The suggestion to be made in this connection is a simple one: The 

 sooner the fruit is cleaned after it is picked the more easily the 

 cleaning can be done and the less risk of damage there is to the 

 fruit. In any event, fruit should be cleaned before it has passed 

 the firm stage of maturity. To accomplish this the following factors 

 should be considered : 



(1) Harvesting the fruit at the proper, stage of maturity; (2) co- 

 ordination of the picking and packing operations as much as possible, 

 so that the harvested fruit will be subjected to a minimum of delay 

 before it is cleaned and packed; and (3) holding the fruit in the 

 coolest space available, preferably in cold storage, if cleaning and 

 packing are unavoidably delayed after it has been picked. 



Commercial experience has demonstrated that when proper pre- 

 cautions are taken fruit can be washed or dry cleaned in such a man- 

 ner as to cause no commercially significant increase in decay or 

 deterioration in storage. It has demonstrated that certain cleaning 

 practices and certain types of equipment are not suitable for cleaning 

 fruit. When these are avoided and sanitary conditions are provided 



