Phytoplasma infections in plants are known to influence their interactions with aboveground herbivores, yet their impact on belowground herbivores remains largely unexplored. In cranberry, infection by the phytoplasma Candidatus Phytoplasma sp. subgroup 16SrIII-Y leads to false blossom disease. This study investigated the effect of this infection on the performance and feeding behavior of both a foliar feeder (spongy moth) and a root feeder (oriental beetle). Using phytoplasma-infected and uninfected cranberries of two genotypes ('Ben Lear' and 'Crimson Queen'), we measured the survival, growth, and consumption rates of spongy moth and oriental beetle larvae. Additionally, to assess the impact on plant morphological and chemical traits, we examined the effect of phytoplasma infection on shoot and root growth, carbon and nitrogen content, and levels of defensive compounds such as proanthocyanidins (PACs). Results indicate that larvae of the spongy moth and oriental beetle generally exhibited larger size and more efficient tissue consumption on infected plants. However, these effects varied by cranberry genotype, possibly due to differences in phytoplasma titer. Phytoplasma infection correlated with stunted growth, elevated nitrogen content, and lower PAC levels in both shoots and roots of infected cranberry plants compared to uninfected ones. These findings suggest that phytoplasma infection manipulates plant chemical composition by increasing nutrient levels and decreasing defensive compounds, thereby enhancing herbivore performance both above and belowground. This study highlights the intricate interplay among plants, phytoplasma infection, and insect herbivore communities.
.png)
