Trade‐off in oviposition strategy: choosing poor quality host plants reduces mortality from natural enemies for a salt marsh planthopper

Abstract

Abstract 1. Both host plant nutrition and mortality from natural enemies have been predicted to significantly impact host plant selection and oviposition behaviour of phytophagous insects. It is unclear, however, if oviposition decisions maximise fitness.2. This study examined whether the salt marsh planthopper Pissonotus quadripustulatus prefers higher quality host plants for oviposition, and if oviposition decisions are made so as to minimise mortality at the egg stage.3. A controlled laboratory experiment and 4 years of field data were used to assess the rates of planthopper oviposition on higher quality ‘green’ and lower quality ‘woody’ stems of the host plant Borrichia frutescens. The numbers and percentages of healthy eggs and eggs that were killed by parasitoids or the host plant were recorded.4. In all years, including the laboratory experiment, Pissonotus planthoppers laid more eggs on lower quality woody stems than on higher quality green stems. While host plant related egg mortality was higher in woody stems, the percentage of eggs parasitised was much greater in green stems. This resulted in a lower total mortality of eggs on woody stems.5. The results of this study demonstrate that, although Pissonotus prefers lower quality host plants for oviposition, this actually increases fitness. These data seem to support the enemy free space hypothesis, and suggest that for phytophagous insects that experience the majority of mortality in the egg stage, oviposition choices may be made such that mortality is minimised.