STICKY RED SPHERES FOR TRAPPING APPLE MAGGOT FLIES 



Ronald J. Prokopy 

 Department of Entomology 



In the last issue o£ Fruit Notes, I discussed the visual and 

 odor cues that guide apple maggot flies to insect honeydew, their 

 principal source of food. I mentioned that the honeydew accumu- 

 lates principally on tree leaves, and that both the color of leaves, 

 as well as the odor of honeydew are attractive to the flies. I al- 

 so briefly described experiments which showed that daylight fluo- 

 rescent yellow paint is, to the flies, the equivalent of super- 

 bright and therefore super-attractive foliage, and that small sticky 

 coated rectangles painted this color are effective in attracting 

 and capturing flies which are in a feeding mood. Ammonium acetate 

 and protein hydrolysate emit odors which are apparently similar to 

 the odors emitted by honeydew, and these materials, when added to 

 the yellow rectangles, further enhance their effectiveness in cap- 

 turing food-seeking maggot flies. 



To infest apples, apple maggot flies must of course not only 

 find food but also succeed in finding mates and apples in a stage 

 susceptible for egglaying. In this article, I wish to briefly de- 

 scribe some of the research which I (alone, or in conjunction with 

 Guy Bush of Texas and Volker Moericke of West Germany) have been 

 doing in recent years to determ.ine how these flies find mates and 

 apples. This research has yielded a trap which from mid-season on, 

 is even more effective than the odor-baited yellow rectangles in 

 capturing and monitoring fly populations in commercial orchards. 



Apple maggot females must mate in order to lay fertile eggs. 

 We have found that the site of mating is exclusively the fruit of 

 the larval host plant. The original larval host of the apple mag- 

 ,got, an insect native to North America and not found elsewhere, is 

 hawthorn Apples were introduced into the U.S. from Europe by early 

 pioneers about 350 years ago. About 110 years ago, the apple mag- 

 got shifted from hawthorn onto apples, and about 20 years ago it 

 shifted onto sour cherries in Wisconsin. Thus, the mating site of 

 the flies is the fruit of hawthorn, apples and sour cherries. 



How do the males and females locate fruits favorable as mating 

 and egglaying sites? We have found that the odor of apples in a 

 stage suitable for egglaying, in combination with the general vis- 

 ual stimulus of apple tree color, size and shape, attracts both 

 sexes of flies to apple trees. If the apples on a tree are not ripe 

 enough for egglaying, or if they're too ripe, then their odor does 

 not attract the flies. After the flies arrive on an apple tree, 

 both sexes locate the individual fruits principally, if not exclu- 

 sively, by vision. I showed this by hanging wooden models of ap- 



