Cultural and chemical pest control methods alter habitat suitability for biological control agents: an example from Wisconsin commercial cranberry

An integrated pest control program requires an in-depth understanding of the compatibility of all control strategies used. In Wisconsin commercial cranberry production, early-season control strategies include either a broad-spectrum insecticide application or an alternative 30- to 40-hour-long flood. Both of these actions have the potential to not only directly impact the community of native natural enemies, which are important for biological control of pest species in the cranberry system, but also to affect them indirectly by altering food-web dynamics. For instance, the flood, and the corresponding removal of detritus and detritivores, may either lead to predator starvation (reduced biocontrol potential), or to predator prey-switching away from detritivores and toward pest herbivores (increased biocontrol potential). To determine to compatibility of the spring flood with biological control in commercial cranberry acreage, we measured densities of arthropods belonging to detritivore, herbivore, and predator guilds, along with predation rates, in beds that were flooded compared to those that instead received a corresponding insecticide application. Flooding led to an increase in predator density. Detritivore and herbivore densities were the same in flooded as in sprayed beds. These results suggest that increased predation rate may at least partially contribute to pest suppression following the spring flood, with implications for grower practices and for theoretical ecology.