Plant-provided food increases indirect defense through manipulation of a mutualism: efficacy in the field and potential in the greenhouse

Abstract: A protective mutualism between sticky plants and predatory insects has recently been described: plants covered in glandular trichomes trap carrion which predators feed on, increasing their abundance. The increase in predator abundance reduces herbivory and increases plant fitness. Thus far this indirect defensive strategy has only been assessed on wildflowers in natural systems. In this study we have demonstrated that this protective mutualism exists between flue-cured tobacco and the predator Jalysus wickhami. By adding Drosophila spp. carrion to tobacco plants we were able to manipulate carrion abundance in the field and assess predator, pest, and plant responses. Predator abundance increased in response to carrion augmentation while herbivore abundance did not differ from controls. However, damage to plant reproductive structures decreased with increased carrion. Our results indicate that arthropod carrion may be an alternative food resource for predators associated with plants covered in glandular trichomes, increasing their abundance and reducing herbivory. Protective mutualisms between predators and economically important sticky plants should be considered within the context of integrated pest management as a novel approach to conservation biological control. Augmenting carrion or manipulating agroecosystems to increase carrion abundance is possible in several production systems and could contribute to pesticide use reduction.