-3- 



Apple Maggot Flies 



Apple maggot flies, prior to reaching sexual maturity, make 

 frequent visits to apple tree leaves, where they feed on insect 

 honeydew and other surface substances, and rest. After reaching 

 sexual maturity, they make frequent visits to the fruit, where 

 they mate and lay eggs. Visits to the twigs and branches are 

 infrequent. 



A green rectangle of medium size (6x9 inches) roughly 

 mimics the hue reflectance pattern and form of clusters of apple 

 foliage. While apple maggot flies will alight on such a green 

 rectangle, they alight in much greater numbers on yellow rect- 

 angles, which have the same sort of hue reflectance pattern as 

 apple leaves, but reflect light at a much higher intensity than 

 leaves. It seems as though the flies perceive yellow rectangles 

 as being super-bright or super-normal clusters of foliage. Day- 

 light fluorescent yellow is an especially bright and attractive 

 hue . 



When baited with an odoriferous substance such as an ammon- 

 ium acetate-protein hydrolysate combination (which apparently 

 mimics the smell of insect honeydew), and coated with Tangletrap, 

 daylight fluorescent yellow rectangles are excellent for monitor- 

 ing populations of food-seeking flies. 



A yellow or green 2-inch diameter sphere closely mimics the 

 hue reflectance pattern, form, and size of a developing apple. 

 While mature apple maggot flies readily alight on such spheres, 

 they alight in considerably greater numbers on red, violet, and 

 black spheres 3-5 inches in diameter. It seems as though these 

 dark colored spheres, on the basis of greater contrast against 

 the background, are more readily detectable by the flies than 

 are the light colored ones -- much the same as humans can more 

 easily locate red apples than yellow or green apples in a tree. 

 Apparently the flies view large spheres as being super-large or 

 super-normal apples. Our studies have shown, however, that if 

 a sphere is overly large--for example, 12 inches diameter--it 

 is less likely to be viewed as an apple and in fact attracts 

 fewer flies than a 3 1/2-inch sphere. 



When coated with Tangletrap, 3 1/2-inch diameter red spheres 

 provide excellent traps for monitoring populations of apple maggot 

 flies seeking mating and egglaying sites. 



In 1978, we compared 6x9 inch odor-baited yellow rectangles 

 (sold commercially as Pherocon AM Standard Traps by Zoecon Corp., 

 Palo Alto, California) with 3 1/2-inch diameter dark red spheres 

 coated with Tangletrap in 16 commercial and 4 abandoned Massa- 

 chusetts apple orchards. Although early-season maggot fly cap- 

 tures in the abandoned orchards were slightly greater on the yel- 

 low rectangles than on the spheres, captures in the commercial 

 orchards were consistently earlier and consistently greater in 

 weekly and total numbers on the spheres than on the rectangles. 



