An integrated pest management program for burrowing shrimp control in oyster aquaculture

Abstract

Integrated pest management is widely applied in terrestrial agriculture, but less so in aquaculture. Parallels to insect control in agricultural fields were exploited in this application of integrated pest management principles to control burrowing shrimp Neotrypaea californiensis and Upogebia pugettensis in Pacific Northwest U.S.A. oyster aquaculture. The pesticide carbaryl has been applied to oyster aquaculture tracts to control burrowing shrimp in Washington state coastal estuaries for over 40 years. Infestations of these shrimp reduce the stability of the bottom substrate where oysters are raised and cause them to be covered with sediment and die. The use of carbaryl to control these shrimp continues to receive scrutiny despite substantial evidence that there are few if any long term environmental impacts, and the industry recently agreed to limit this practice and implement integrated pest management. The efficacy of the current control program was investigated and a monitoring plan which achieves level 1 goals of an integrated pest management program is described. While the pesticide was found to be 84–96% effective at removing shrimp from a given bed, new individuals can recruit back to these beds as post-larvae on an annual basis. Shrimp recruitment was low during the years of this study (1999–2002), and most monitored beds remained relatively shrimp free after treatment compared to previous records from the early 1990's when shrimp recruited more frequently and higher burrow densities were recorded on oyster beds. Some monitored beds were re-treated with pesticide during this study under the guidelines of the current pesticide application program (threshold of 10 shrimp burrows m − 2 ). An attempt to experimentally define a true injury threshold as the basis of an economic action threshold for pesticide treatment, indicated that shrimp cause substantial oyster losses at levels exceeding 20 to 40 shrimp burrows m − 2 . Further refinements seem unlikely given the perennial nature of this crop and a multitude of market and environmental variables affecting both crop and pest. Instead, we propose the use of an empirical decision tree in conjunction with a shrimp monitoring program to implement integrated pest management, regardless of whether the pesticide or alternative control measures are chosen as the final tool(s) for shrimp control.