-2- 



In 1953 it was foiuKl/that a solvent containing benzene, isopropyl, 

 alcohol, and Tween 20— 'would reduce DDT residues enough to make 

 the apples usable in rearing work. Benzene is a better solvent than 

 isopropyl alcohol for the chlorine and phosphorus insecticides, but it 

 damages the tissue of the fruit more. The damage consists of brown 

 pitted areas just beneath the skin (fig. 2). When the pits are 1 mm. or 

 less in diam.eter, treated fruit can be held for several weeks after 

 washing. It was found after testing several formulations that good 

 solvent action and relatively low damage were obtained with a mixture 

 containing 20 parts of benzene to 80 parts of 99-percent isopropyl 

 alcohol (by volume), to which 60 grams of Tween 20 per liter was added. 



The washing is done outdoors or in a well-ventilated shelter, pre- 

 ferably when the temperature of the solvent is 70-80° F. Heavy 

 neoprene gloves protect the skin from the residue- contaminated solvent. 

 Five earthenware crocks are used in the washing and rinsing (fig. 3). 

 The first two are two-thirds filled with the solvent, each from a separate 

 carboy and provided with metal covers; the other three are filled with 

 water. The apples are placed in a cylindrical basket with a cover made 

 of heavy screen wire and mounted on a broom handle to act as a plunger. 

 The basket should be about half as tall as the crock and slightly less 

 than its diameter. The basket containing apples is worked vigorously 

 up and down in the first jar of solvent for 10 seconds, then quickly trans- 

 ferred to the second jar for a second washing of 10 seconds, drained 

 quickly, and emptied into the first rinse. The whole exposure to solvents 

 should not take much mor-e than 30 seconds, particularly if the temper- 

 ature of the solvent is above 80*^ F. In the rinse the apples are agitated 

 and ladled from one crock to another, and finally to racks, where they 

 are left for an hour or two until dry and free of benzene fumes. After 

 drying, the apples if kept in cold storage will remain suitable for rearing 

 work for several weeks. The solvent may be used for many washes. 

 When the first wash becomes befouled with trash, dirt, and precipitated 

 material, it is replaced with fresh solvent, and exchanged with the 

 second wash, now moved up to the first position. The rinses are rotated 

 in the same manner, the changes being made frequently so that the third 

 rinse is always free of soapy bubbles. 



In 1953 numerous tests were made with immature apples obtained 

 from orchards sprayed with DDT. It was found that unwashed apples 

 having DDT residues were very toxic to adults of the oriental fruit moth 

 parasites Horogenes molestae (Uchida) and Macrocentrus ancylivorus 

 Roh., and moderately so to Phanerotoma grapholithae Mues. and Agathis 



2] The author requested R. D. Chisholm and Louis Koblitsky of the 

 Pesticide Chemicals Research Section to suggest a solvent which would 

 remove DDT residues from immature apples. They prepared the mix- 

 ture described above which was tested by the author. 



