ORCHARD INSECTS OF THE PACIFIC NORTHWEST 7 



poor condition. In many cases stationary spraying systems are much 

 more efficient than portable outfits. 



A number of insecticides may be used for controlling the codling 

 moth. Chief of them is acid lead arsenate. The powdered form is 

 ordinarily used at the rate of 2 pounds to 100 gallons of water, but in 

 severely infested orchards this quantity may be increased to 3 pounds. 

 Fish oil and certain colloidal materials, ordinarily known as spreaders, 

 may be used to advantage to cause a larger quantity of lead arsenate 

 to adhere to the fruit, or to prevent blotching. Fish oil may be used 

 in the proportion of 1 pint or 1 quart to 100 gallons of spray, and other 

 spreaders may be used in the proportion of % pound to 100 gallons of 

 spray. If lime-sulphur solution must be used for the control of scab 

 or powdery mildew, it may be combined with the lead arsenate. The 

 lime-sulphur should be put into the tank while it is being filled, and 

 the lead arsenate added just before beginning to spray. The mixture 

 should be used at once on account of a chemical reaction which occurs. 

 This reaction may be retarded by putting casein spreader or hydrated 

 lime into the tank before the other materials are added, using them 

 at the rate of 1 pound to 100 gallons of spray. 



Residues of arsenic and lead in excess of the tolerances permitted by 

 the Federal Food and Drug Administration must be removed by wash- 

 ing or wiping before the fruit is sold. Although this is not ordinarily 

 difficult, 2 the grower should avoid spray schedules that may result in 

 excessive residues. The tolerance for lead now permitted does not 

 make it possible to use lead arsenate for the second brood, and con- 

 templated restrictions may stop its use altogether. It may be pos- 

 sible to use arsenicals not containing lead, such as calcium arsenate 

 or manganese arsenate, although these materials may cause burning 

 and do not usually control as well as the lead arsenate. 



Mineral-oil emulsions (p. 68) are very valuable for controlling the 

 codling moth if used in conjunction with the arsenical or some other 

 material. One gallon of the emulsion to 100 gallons of spray is 

 sufficient, and not more than 4 applications should be made in a 

 season. Oil emulsions may cause a severe drop of fruit and foliage 

 if applied on trees that have received sulphur sprays within 2 

 months. Therefore, when the use of sulphur sprays is necessary for 

 the control of apple powdery mildew or other fungous diseases, oil 

 cannot be used with safety in the early cover sprays. Oil may be 

 used most effectively when most of the eggs are on the trees, since 

 its chief value lies in its ability to destroy eggs. It will generally be 

 most valuable if added to the second and third cover sprays for the 

 first brood, and to one or more sprays for the second brood. Since 

 it also causes the lead arsenate to adhere more firmly to the fruit and 

 foliage, there will be difficulty in removing the spray residue if the 

 combination of oil emulsion and arsenical is used in the second-brood 

 sprays. For these late sprays nicotine sulphate (40 percent nicotine) 

 may be combined with the oil emulsion very effectively in place of the 

 arsenical, using it in the proportion of one half to two thirds of a pint 

 to 100 gallons of spray. In the arid valleys, also, cryolite (sodium 

 fluoaluminate), in the proportion of 3 or 4 pounds to 100 gallons, may 

 be used in the second -brood sprays. This material should not be 

 used alone but only in conjunction with an oil emulsion or with fish 



2 Detailed instructions for removing spray residues may be found in Farmers' Bulletin 1687, Removing 

 Spray Residues from Apples and Pears. 



