6- 



predict its future in Massachusetts. 



The Medfly is a close relative of the apple maggot fly. Both 

 are members of the same subfamily, and both have similar behavior. 

 The main differences are twofold: (1) the Medfly attacks 253 

 different species of fruits, nuts, and vegetables, while the apple 

 maggot fly attacks only six, and (2) the Medfly cannot readily 

 survive cold conditions while the apple maggot fly can easily 

 overwinter in very cold regions or as pupae in the soil. 



What are the principal fruits grown in Massachusetts which are 

 potential favorable hosts for the Medfly? The most favored one 

 would probably be peaches, followed (but not necessarily in order) 

 by nectarines, apricots, plums, cherries, apples, and pears. 

 Occasional host fruits include grapes, peppers, and tomatoes. 



Where did the Medfly come from? It originated in tropical 

 West Africa, spread to north and south Africa, and then in the 

 1800's moved into Spain, France, Italy, Greece, and the Middle 

 East. It arrived in South America in 1901, Hawaii in 1907, Costa 

 Rica in 1955, and northern Guatemala in 1977. It has remained 

 firmly established in all of these countries ever since. 



The first record of Medfly infestation in the USA occurred 

 in 1929 in Florida. Since then, it has re-entered Florida thrice 

 more (1956, 1962, and 1963), Texas in 1966, the Los Angeles area 

 in 1975 and again in 1980, and finally, in June of 1980, the Santa 

 Clara County area of Central California. Biochemical genetic 

 analysis studies suggest that the flies which entered Santa Clara 

 County probably came from Central or South America. 



Except for this last infestation, the Medfly in the USA has 

 in each case been successfully eradicated through ground or aerial 

 application of insecticide bait sprays, aided by fruit stripping. 

 In the present central California outbreak, an attempt was made 

 to achieve eradication through a combination of sterile male 

 releases to render female eggs infertile (more than 100 million 

 sterile flies per week were released for several months), stripping 

 of susceptible fruits from plants, and ground applications of 

 malathion bait sprays. Because these combined techniques did not 

 prove successful, state and federal agencies have been recently 

 obliged to resort to the only proven method of eradicating Medflies 

 from substantial pockets of infestation in the USA: aerial appli- 

 cation of malathion bait sprays. 



This article is not aimed at debating the merits of aerial 

 application of pesticide for Medfly eradication vs. the possible 

 injury that may result to those few individuals which may be highly 

 susceptible to deleterious effects of malathion (as with bee stings, 

 we can expect purely on the basis of probability that a small per- 

 centage of people in every population are inordinately susceptible 



