MARKET DISEASES OF FRUITS AND VEGETABLES 9 



apples rapidly from the merchant to the consumer and keeping 

 them as cool as possible help in preventing spoilage. 

 (See 11, 12, 59, 111>.) 



Ammonia Injury 

 (See Pears, Ammonia Injury, p. 56; pi. 5, C.) 



Apple Maggot Injury 

 (Rhagoletis pomonella (Walsh) ) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



The injury caused by the apple maggot, which is often found 

 in apples grown in the northeastern part of the United States, 

 consists in small tunnels winding through the flesh. There may 

 be little or no external evidence of infestation. Affected fruits 

 are likely to be misshapen. Most of the damage is done on sweet 

 or subacid varieties of summer and fall apples, but winter varie- 

 ties do not entirely escape. 



The maggots have been found to distribute through the interior 

 of the fruits bacteria and molds, which cause the flesh to rot 

 and break down and make badly infested fruits of the early 

 varieties drop prematurely. In the fruits of winter varieties 

 which fail to drop, the maggots are usually killed by the pressure 

 of the rapidly growing tissues; the tunnels remain as brown 

 woody streaks through the flesh (pi. 15, A) and make the fruit 

 less suitable for eating raw or cooking. A small amount of injury 

 results from the egg laying of the flies. The flesh immediately 

 surrounding the egg punctures sometimes fails to grow, and there- 

 fore there are dimplelike depressions in the surface. 



The apple maggot, or railroad worm, is a footless white or 

 cream-colored larva, usually about % inch long when full-grown. 

 The adult form is a fly, somewhat smaller than a housefly, which 

 emerges from the soil during late June, July, or early August, 

 depending on the locality. The flies make tiny punctures in the 

 skin of the fruit and place their eggs just underneath. The 

 eggs have a short period of incubation ; in hot weather they hatch 

 in 4 to 6 days. The period spent by the maggot in the fruit 

 varies greatly but may be as short as 2 weeks. When mature, the 

 maggots leave the fruits, which by this time have fallen to the 

 ground, enter the soil, and form puparia which resemble grains 

 of wheat. Within the puparia the insects transform to the adult 

 stage. They emerge the following summer or sometimes the second 

 summer. 



CONTROL MEASURES 



Satisfactory control of the insect has been obtained by spraying 

 the trees with lead arsenate at the proper time in the summer, 

 thus killing the adults before they lay their eggs. Usually two 

 applications of lead arsenate at a strength of 2 pounds in 100 

 gallons of water, with an interval of approximately 2 weeks 

 between, have been sufficient. This program is likely to result in 

 enough residue to require removal. In recent years workers in 

 New York State have obtained satisfactory control of apple 



