Blueberry maggot monitoring underway

Male blueberry maggot fly on an unripe blueberry. Photo: Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org

As part of a NC Blueberry Council, Inc. funded project to develop insect pest monitoring programs for blueberries, our lab has been trapping weekly to determine the population density of blueberry maggot (Rhagoletis mendax) in North Carolina blueberry growing regions.

The blueberry maggot is a true fruit fly (Family Tephritidae), with 1 generation per year in NC. Blueberry maggot has a narrow host range, feeding on commerical blueberries and their close wild relatives. Blueberry maggot can be an extremely serious pest in blueberries. The larvae (maggots) feed internally in fruit and damage can be very hard to detect on the surface. If left unchecked, blueberry maggot infestations can be extremely high, but in North Carolina, the extensive use of pesticides and relatively concentrated commerical blueberry growing region has resulted in suppression of blueberry maggot populations to below detectable levels in many areas.

Blueberry maggot larvae exiting fruit before pupation. Photo: Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org

Most large blueberry growers in NC export at least part of their crop to Canada, which imposes quarantine restrictions on blueberries imported from areas where blueberry maggot is found. In order to be accepted for import into Canada, growers must comply with the Canadian Food Inspection Agency's phytosanitary requirements, which require 1 of 2 blueberry maggot management strategies be adopted. The Calendar Spray Program requires pesticide treatments (of any material registered for blueberry maggot and recommended by local extension personnel, in other words, me) begin at first trap capture and continue every 7-10 days through the end of harvest. The IPM Program requires that each farm be monitored for blueberry maggot flies with yellow sticky traps baited with an ammonia food lure at densities specified by the quarantine protocol. Growers in the IPM Program apply pesticide only if a blueberry maggot fly is caught and make a minimum of 2 applications. If no further flies are caught, pesticide applications cease until the next trap capture. The North Carolina Department of Food, Agriculture & Consumer Services (NCDA & CS) oversees the certification program for blueberry maggot and have 0nly worked with growers using the calendar program. See NCDA & CS's notification letter for this year here.  Our trapping effort is designed to provided both blueberry growers and NCDA & CS with the information necessary to allow interested growers to implement the IPM program in the coming years, and hopefully to reduce pesticide applications.

Yellow sticky (AM) trap baited with an ammonia lure. Photo: Michigan State University IPM

This program covers 14 separate fields which total just over 1500 acres in Bladen and Pender Counties and includes a total of 149 individual traps. Two additional sites in Rockingham County, NC are also be monitored because these locations have a history of blueberry maggot infestation, while our eastern NC sites have not had detectable blueberry maggot populations for at least the last 3 years.

To date, we have captured only 1 blueberry maggot fly, a male caught during the week of May 17th. The grower is certified by NCDA & CS under the calendar spray program, so he was scheduled to begin treatments that week and to continue treating weekly until the end of harvest. No additional trap captures at this, or any other, farm have occurred thus far. If trap captures remain this low through the remainder of the season, there is real potential to decrease the number of pesticide treatments applied in the future.

Blueberry maggot fly trap captures to date are updated weekly, and all changes can be seen in real time here.

For more information:
Phytosanitary requirements for the importation from the continental United States and for the the domestic movement of commodities regulated for blueberry maggot

Burrack Lab trapping data

NC Blueberry Council, Inc.