Best management practices for the control of blister worm on oyster farms

Project Overview

Project Type: Research and Education
Funds awarded in 2014: $61,742.00
Projected End Date: 10/31/2018
Grant Recipient: University of Maine
Region: Northeast
State: Maine
Project Leader:
Dr. Paul Rawson
University of Maine

Annual Reports

Information Products


  • Animals: shellfish


  • Animal Production: parasite control, preventive practices
  • Education and Training: farmer to farmer, on-farm/ranch research
  • Pest Management: field monitoring/scouting, physical control, weather monitoring
  • Production Systems: holistic management

    Proposal abstract:

    Blister worm, a polychaete worm that burrows into the shells of oysters, was first recognized as a serious pest in Australia in the 1890s; as the number and size of oyster culture operations in the Northeast has expanded, so too has the incidence of blister worm. Blister worm increases the oyster shell’s brittleness, thus hampering harvesting; creates visible pockets (blisters) of mud and waste that mar the oyster’s appearance when served on the half-shell; and, if the blister is broken, the resulting off-flavor causes catastrophic impacts on market value of farmed oysters. Anecdotal remedies, such as brine dips, to treat infested oysters are ineffective. Currently, the best remedy places oysters in cold, dry storage for several weeks which is costly, increases crop loss, and disrupts production cycles. This project will test changes in husbandry practices targeting the onset of pest infestation to eliminate the need for costly treatment of infested oysters and use a variety of outreach methods to communicate best management practices for controlling blister worm to oyster farmers in the region.

    Performance targets from proposal:

    Objectives - Reducing the impact of disease-causing and pest species has been a top priority for oyster growers in the Northeast. Breeding programs have reduced the impact of disease, but not the incidence of blister worm. Because infestations affect the marketability of oysters, they have the greatest impact on culture operations at the end of the production cycle; growers in the Northeast are particularly concerned with crop loss and loss of market share as infestations increase in severity. Blister worm has a dispersive larval stage; our hypothesis is that recently settled, young blister worms will be more sensitive to preventative treatments than older worms that have established burrows. Our research will test treatments designed to kill recently settled blister worms before they can burrow into and infest oysters. These non-chemical, ecologically sustainable treatments can be readily incorporated into normal culture operations to minimize labor and other production costs associated with pest management, and reduce the oyster mortality currently incurred when farmers use the only known effective remedy for established adult blister worms. Our proposed education program will increase farmer knowledge about blister worm, proposed treatments and how and when to apply them. This project will directly involve two farms in Maine and through our education program we expect to reach over 100 additional farmers in the northeastern U.S.


    Performance Target - Twenty northeastern oyster farms with annual aggregate sales of about $4 will each implement a comprehensive polychaete pest management plan. This will reduce pest prevalence and improve crop quality compared to prior years, avoiding an estimated $4 million aggregate loss in annual sales.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.