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How to Position Visual Traps in Trees 



Proper use o£ visual traps demands more careful attention 

 to trap placement than is the case with sex pheromone traps. 

 The visual traps, best hung from branches on the south side of ap- 

 ple trees at heights of 20-40 inches for plant bugs and 6-8 

 feet for sawflies and maggot flies, must be readily visible to 

 insects approaching from any direction. It is advisable, there- 

 fore, to remove all foliage and fruit within 12 inches or so of 

 the sides, top, and bottom of a trap. Beyond this distance, 

 however, there should be as many buds, blossoms, leaves, or 

 fruits as possible to attract insects into the general area. 

 Presently, we are using one visual trap of each type per 2 acres 

 of trees in our pest management orchards. 



Relation Between Trap Captures and Insect Injury Levels 



The ultimate proof of the usefulness of such visual traps 

 lies, of course, in the accuracy with which trap captures esti- 

 mate numbers of injury-causing adults actually present in the 

 orchard. In 1978, we therefore made an attempt to establish 

 indices relating levels of trap capture to levels of injury 

 caused by each pest. We hung 6-10 traps of each type in each 

 of 16 commercial orchards. 



The results showed the following correlation values of trap 

 captures with injury levels (+ 1.00 would be a perfect positive 

 correlation, indicating a perfect relationship of trap captures 

 to injury levels): (a) apple maggot captures on red spheres with 

 apple maggot egg-laying stings, + 0.87 (b) sawfly captures on 

 non-ultraviolet reflecting white rectangles with sawfly injury 

 scars on mature fruit, + 0.82; and (c) plant bug captures on non- 

 ultraviolet reflecting white rectangles with abscission of devel- 

 oping buds caused by plant bug feeding, + 0.67. 



These high positive correlation values are very encouraging 

 and suggest that prospects are good for establishing reliable 

 indices relating visual trap captures to insect injury levels, 

 and therefore for using visual trap captures as a basis for de- 

 ciding if or when pesticide treatments against plant bugs, saw- 

 flies, and apple maggot flies are economically merited in a given 

 block of trees. We hope that our studies during the next 2-3 

 years will refine and validate the initial indices obtained in 

 1978. Until then, the principal value of the visual traps will 

 be in detection of the first appearance and the disappearance of 

 these pest adults in orchards. 



