OKCHARD INSECTS OF THE PACIFIC NORTHWESQ 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 m 

 severely infested orchards tins 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 % to % 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 or lead, in quantities sufficiently great to consti- 

 tute a menace to the health of the consumer, must be removed by 

 washing or wiping before the fruit is sold. Although this is not ordi- 

 narily difficult, 2 the grower should avoid spray schedules that may 

 result in excessive residues. Calcium arsenate, which contains no 

 lead, may be used for light infestations, although this material may 

 cause burning and does not usually control as well as 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 lor 

 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 (he second-brood 

 sprays. In place of the arsenical,' nicotine sulphate (40 percent 

 nicotine) may be combined with the oil emulsion, using it in the 

 proportion of }{ to % of a pint to 100 gallons of spray. Since 

 this combination interferes greatly with residue removal, not 

 more than 2 or 3 applications of lead arsenate should be made preced- 

 ing its use. In the arid valleys, also, cryolite (sodium fluoaluminate), 

 in the proportion of 3 or 4 pounds to 100 gallons, may be used m the 

 second-brood sprays. This material should not be used alone but 

 only in conjunction with an oil emulsion or with fish oil. Excessive 



2 Detailed instructions for removing spray residues may be found in Farmers' Bulletin lfi87, Removing 

 Spray Residues from Apples and Pears. 



