Materials & Methods 



Pesticide degradation and detoxification . 

 Enterobacter agglomerans, a bacterium found 

 to inhabit both the gut of the apple maggot fly 

 and apple leaf surfaces in nature, was added to 

 sterile preparations of azinphosmethyl at a con- 

 centration typical of one sprayed by a grower. 

 The bacteria/pesticide solutions and sterile pes- 

 ticide solutions (void of any bacteria) were incu- 

 bated at 73°F for 3 days. Cholinesterase was 

 extracted from apple maggot flies and mixed 

 with the bacteria/p)esticide solutions to deter- 

 mine whether or not azinphosmethyl still was 

 capable of reducing cholinesterase activity after 

 exposure to the bacteria. Also, small amounts 

 fi-om each sample were fed to 25 apple maggot 

 flies and mortality values were recorded at 24- 

 and 40-hour intervals. Additionally, the solu- 

 tions were analyzed for degradation products of 

 azinphosmethyl. The experiment was done twice. 



Plant allelocompound degradation and 

 detoxification . We also studied four 

 allelocompounds considered to be toxic to apple 

 maggot and typically found in the habitat of 

 apple maggot flies. They were: naringenin, 

 phloridzin, cafieic acid and cinnamic acid. Each 

 solution was inoculated with Enterobacter 

 agglomerans and incubated at 87°F for 24 hours. 

 Sterile solutions also were incubated along with 

 the bacterial solutions. Degradation of each 

 compound was measured by changes in pH (a 

 typical phenomenon associated with degrada- 

 tion) and by the presence or absence of degrada- 

 tion products. Also, small amounts from each 

 solution were fed to 10 flies individually, and 

 mortality values were recorded after 12 days. 



Results 



Mixing cholinesterase extracted from apple 

 maggot flies with azinphosmethyl resulted in 

 low to no cholinesterase activity (14.8 active 

 units). However, activity of cholinesterase was 

 10 times greater when mixed with 

 azinphosmethyl in which bacteria had grown 

 for three days (144.1 active units). The higher 

 value indicates that cholinesterase activity was 

 not inhibited as much in the bacterial solution 



and therefore, the pesticide was less effective. 

 We found that loss of effectiveness was the 

 result of chemical alteration of azinphosmethyl 

 by bacteria 



Forty hours afl«r a 48-hour-old solution of 

 bacteria and pesticide was fed to apple maggot 

 flies, only three of 50 flies were dead. In con- 

 trast, when flies were fed the sterile pesticide 

 solution, 47 of 50 were dead after 40 hours. Fifty 

 flies serving as controls were fed only water. All 

 were alive after 40 hours. 



In the allelocompound solutions that con- 

 tained bacteria, we saw changes in pH (indica- 

 tive of chemical changes) which were not ob- 

 served in the sterile solutions, and we were able 

 to detect degradation products in the bacterial 

 solutions that were not present in the sterile 

 solutions. Therefore, bacteria also degraded the 

 plant allelocompoiuids. When apple maggot 

 flies were fed sterile solutions of the four 

 allelocompounds, all were dead after 12 days; 

 however, when solutions inoculated with bacte- 

 ria were fed to the flies, none died. 



Conclusions 



Our laboratory findings indicate that 

 Enterobacter agglomerans possesses the abihty 

 to degrade and subsequently detoxify 

 azinphosmethyl and certain plant 

 allelocompounds that normally are toxic to apple 

 maggot flies. This finding is an important first 

 step in establishing the contribution of bacteria 

 toward detoxification of harmful compounds 

 encountered in nature by this and other insects. 



We are continuing our work in this area by 

 studying (1) precisely how the bacteria degrade 

 toxic compounds, (2) how fly longevity and fe- 

 cundity are affected by detoxification, and (3) if 

 detoxification mechanisms inherent to flies are 

 enhanced by degradation processes of bacteria. 

 Further comprehension of ways insects handle 

 chemicals in the environment should contribute 

 to pest management progrguns. Such knowl- 

 edge also may lead to creation of new ways to 

 decrease or eliminate pesticide crops or on spray 

 equipment. For example, it is conceivable that a 

 bacterial or enz)Tnatic preparation could be 

 sprayed on trees before harvest so that the 



Fru'n Notes, Summer, 1994 



