Colorado Potato Beetle Vitality Against Pathogens After Exposure to Predators

Tina Miller

The Colorado potato beetle (CPB) is a key pest of potato crops in Washington. CPB larvae feed on plants aboveground, where they are attacked by predatory insects. Then, CPB pupate in the soil, where they are attacked by pathogens. CPB can be stressed when they are exposed to, but not killed by predators, and this stress might make them more susceptible to pathogens. We tested this hypothesis in field and laboratory experiments where CPB larvae were exposed to predators or a control and surviving pupae were exposed to pathogens. In the laboratory experiment CPB were exposed to predators by attaching a lady beetle or damsel bug to the end of a wooden dowel rod and forcing it into contact with CPB larvae. CPB not exposed to predators were contacted with a dowel rod alone. Following contact, we recorded the behavior of larvae to determine how they responded to each treatment. After larvae had completed development, we placed them in plastic deli cups containing soil with fungi and nematodes and recorded survival to the adult stage. This allowed us to determine if CPB previously exposed to predators had differing levels of mortality. In our field experiment we placed CPB larvae with potato plants in mesh cages and exposed them to both a combination of predator and density treatments. This exposed them to four different treatment combinations while they developed to their final instar stage. Resulting pupae were exposed to fungi and nematodes as in the laboratory experiment. Once again survival to adulthood was recorded. Our results revealed that predators decreased the CPB’s resistance to pathogens, suggesting predators and pathogens likely act in a complementary way to control CPB. CPB survival to adulthood after pathogen exposure was not significantly effected by the density treatment. If it is true that predators and pathogens can act in a way to suppress CPB pests, this experiment may add important knowledge to the field of agriculture by providing insight into naturally controlling pests without using harmful insecticides.

Colorado Potato Beetle Vitality Against Pathogens After Exposure to Predators

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