AIRBLAST SPRAYERS FOR ORCHARD SPRAYING-*" 



Kenneth D. Hickey 

 Pennsylvania State University Fruit Research Laboratory 

 Biglerville, PA 17307 



Airblast orchard sprayers which form, transport, and deposit 

 water droplets onto all above ground parts o£ trees are essential 

 to the commercial production of deciduous fruit crops in eastern 

 fruit growing areas. One characteristic which these sprayers have 

 in common is a fan that generates the mass of air which carries 

 droplets of pesticide suspensions to the target area. The manage- 

 ment and control of all major orchard pests affecting leaves, twigs 

 and fruit (diseases, insects and mites) is dependent upon timely 

 pesticide sprays applied to all areas of the tree. In orchard 

 spraying, the spray target often is not the specific pest being 

 controlled (insect, mite or fungus spore) but rather the leaves or 

 fruit on which it may be present or to which it may visit after the 

 spray has been applied. The target, thus being the tree which is 

 extremely variable in size, shape, density, and row spacing, has 

 created a need for different types of sprayers. Sprayer manufactur- 

 ers responding to these needs have produced airblast sprayers which 

 are so diverse that a grower in America can buy just about any 

 type he may need for his orchard operation. 



Because of the gradual change from standard size trees to 

 semi-dwarf and dwarf types most growers in the mid-Atlantic states 

 have needs for a sprayer that can be used to spray conventional 

 size standard apple trees as well as dwarf apple, peach and cherry. 

 The amount of spray mixture used per acre is another variable that 

 has to be adjusted depending on tree type and size. The amount 

 commonly used varies from 400 gal/A (gpa) in dilute sprays for 

 mature standard apple trees to 10-20 gpa with low volume sprayers. 

 Ultra low volumes of as little as 1.0 to 3.0 gpa have been used 

 with special sprayers but this usage is still very limited. With 

 this magnitude of variation in tree size and spray volume used and 

 the wide range of sprayers available with just about any size tank, 

 it is understandable why growers are often confused when buying a 

 sprayer. To add to the confusion, descriptive phrases such as cfm 

 air volume, air velocity range, dual adjustable blower, axial flow 

 and centrifugal fans, mass median diameter of droplets, shear, disc, 

 mistifier and spinning nozzles, touch command meters, flip over 

 nozzle, and fluid agitation often are used to reveal the wonders of 

 each specific sprayer. 



1 

 Appeared in the Maryland Fruit Grower 49(4): 2-6, 1979 and the 

 Pennsylvania Fruit News . April, ly/y. Reprinted with permission 

 of the author. 



