Residues of Azinphosmethyl on 

 Apples Using First- vs. Third-level IPM 



Starker Wright and Ronald Prokopy 



Department of Entomology, University of Massachusetts 



Scott Carrier, Raymond Putnam, and J. Marshall Clark 

 Massachusetts Pesticide Analysis Laboratory 



The apple maggot fly ( AMF) is a key summer pest 

 of apples in New England and other parts of eastern 

 North America. According to recent surveys, AMF 

 was ranked as one of the two most important insect 

 pests attacking apple fruit by commercial apple grow- 

 ers in Massachusetts [Fruit Notes 61(3)]. AMF are 

 active in orchards from late June through mid-Septem- 

 ber, with peak activity generally in early August. Most 

 growers are able to achieve effective control of AMF 

 by applying two to four insecticide sprays during July 

 and August. 



Over the past two decades, we have attempted to 

 develop an alternative behavioral approach to AMF 

 control. This approach involves surrounding an or- 

 chard block with odor-baited red spheres placed about 

 5 yards apart on perimeter trees. Each sphere is either 

 coated with Tangletrap or is treated with a feeding 

 stimulant and an insecticide to kill alighting flies [Fruit 

 Notes 62(4)]. Ideally, this system of management 

 would allow the grower to cease insecticide applica- 

 tion after plum curculio season, in effect extending the 

 pre-harvest interval for summer insecticide use to 80 

 days or more. One grower-perceived advantage to be- 

 havioral control of AMF is reduction in use of sum- 

 mer insecticides and subsequent reduction in level of 

 insecticide residue on fruit at harvest [Fruit Notes 

 60(4)]. 



The EPA sets standards for commercially accept- 

 able levels of pesticide residue on marketed fruit. 

 Currently, the standard for azuiphosmethyl residue on 

 apples is 2 parts per million (2000 parts per billion). 

 However, the Food Quality Protection Act (FQPA) may 

 strongly affect tolerable levels of residue. The intent 

 of the FQPA is to establish tolerance levels that are 

 ?safe,? defined as ?a reasonable certainty that no harm 



will result from aggregate exposure, including all ex- 

 posure from diet, drinking water, and other non-occu- 

 pational exposures.? In order to calculate health risks 

 associated with exposure to pesticide residues, the 

 FQPA dictates that aggregate exposure be measured 

 by use of a ?risk cup,? meaning that all exposures (fresh 

 and processed foods, water, and household exposure) 

 are combined into the same cup. All existing toler- 

 ances must be re-evaluated, and organophosphate in- 

 secticides (such as azinphosmethyl) are included in the 

 first round of review, slated for completion in August 

 of 1 999. Tolerance levels are based on residues present 

 on fruit at harvest. 



Our aim here was to determine the amount of 

 azinphosmethyl on fniit at harvest in blocks of apple 

 trees that received azinphosmethyl for AMF control 

 versus blocks that received only odor-baited red spheres 

 for AMF control. 



Materials & Methods 



In 1997, we began a pilot third-level IPM project 

 in order to determine the influence of apple tree archi- 

 tecture and planting density on biologically-based pest 

 management and fruit quality. In each of eight com- 

 mercial orchards, we identified and flagged six blocks 

 of trees: two each of high, medium, and low tree den- 

 sity. One block of each density was managed under 

 first-level IPM practices that involved application of 

 two to four sprays of insecticide from early July to 

 harvest. The other block was managed under third- 

 level practices that involved surrounding the block with 

 odor-baited red spheres. For purposes here, fruit were 

 sampled only from the medium-density trees, which, 

 at -240 trees/acre, represent the majority of apple trees 



Fruit Notes, Volume 63 (Number 2), Spring, 1998 



