ANNUAL RF.rORT, 1040 63 



Tiilv 26 to 30 the temperature was 90° to 04°. Relatively hiph humidity 

 accompanied this period of high temperature. Blast appeared in the ex- 

 perimental plots in early August and caused the premature deatii of the 

 plants. Plants never reached normal height and hut few of them bottomed 

 out. Thrips, on the other hand, increased rapidly during late July and 

 early .August, scarred the leaves badly, and hastened the effect of blast 

 on the plants. 



Field tests were made of a fixed nicotine and .SS3 spreader, nicotine 

 sulfate and soap, dual-fixed nicotine and Nufilm spreader, derris (4 per- 

 cent rotenone) and ITltrawet, derris and Nufilm spreader, and flaked 

 naphthalene which was applied to the soil along the rows. 



The fixed-nicotine spray gave good initial control and showed marked 

 residual effect. Derris with Nufilm spreader gave excellent kill and rein- 

 festation was slow. The results were better than when derris was used 

 with Ultrawet as a spreader. Dual-fixed nicotine was not eflfective. 

 Naphthalene flakes gave too uneven results to be dependable. The nico- 

 tine sulfate and soap again proved the most effective of any combination 

 in its initial action, but its residual effects were not so pronounced as 

 those of derris. The early death of the plants, due to blast, before onions 

 were formed made any records on relative yield impossible. 



The Spray Residue Problem. (A. T. Bourne.) Effective August 10, 

 the federal spray residue tolerance for apples and pears shipped within 

 the jurisdiction of the Federal Food, Drug, and Cosmetic Act were raised. 

 The tolerance on arsenic as AsaOs was raised from .01 to .025 grains per 

 pound of fruit, and that on lead as PbO from .025 to .05 grains per pound. 

 This ruling does not apply to fluoride compounds, on which the tolerance 

 of .02 grains per pound is still in force. Neither does the present ruling 

 extend to other food commodities than apples and pears. 



The newly defined limits of tolerance are based on extensive studies 

 by the Public Health Service and upon the recommendations of that body. 

 This action brings a great measure of relief to many growers who have 

 been confronted with increasing demands for more extensive spray pro- 

 grams to cope with increasing abundance of major pests such as apple 

 maggot and codling moth, in the face of more and more stringent enforce- 

 ment of regulations on tolerance. 



Through the cooperation of the Chemistry Department, analyses of 

 samples of Mcintosh from the experimental orchards showed both lead 

 and arsenic residues to be well below the present requirements. Samples 

 from plots receiving the standard schedule of lead arsenate and lime- 

 sulfur in pre-blossom and calyx applications and lead arsenate and 

 wettable sulfur in the cover sprays showed the presence of .006 

 grains of AsjOs and .011 grains of PbO per pound of fruit. Fruit from 

 plots receiving lead arsenate and wettable sulfur throughout the season 

 showed .004 grains of AS2O3 and .011 grains of PbO per pound. Lead 

 arsenate at dosages of 4 pounds (2d cover), 3 pounds (3d cover), and 2 

 pounds (4th cover) per 100 gallons was applied on June 28, July 9, and 

 July 22, respectively. The fruit was harvested September 27 and 28. 

 During this period there was very slight rainfall, especially in August and 

 September when the combined precipitation for the two months was less 

 than half the normal. Even under these conditions the margin of safety 

 was such that no washing or wiping of fruit was necessary to meet the 

 present tolerances. 



