Evaluating French marigold as a border insectary plant for the enhancement of beneficial arthropods in sweet corn plantings

Non-crop flora is often used on arable lands to augment beneficial arthropods in cropping systems. Though there may be an enhancement in the abundance of beneficials, this increase may be limited to crop borders or may not result in greater herbivore suppression. French marigold (Tagetes patula L.) was evaluated as an insectary plant for sweet corn (Zea mays L.) and compared with monoculture sweet corn plots. Several families of parasitoids and predators representing multiple taxa were attracted to marigold plants and more parasitoids were captured on sticky card traps located at the margins of sweet corn plots bordered by marigold as opposed to margins of sweet corn plots without marigold strips. Still, similar numbers of predators and/or parasitoids were found on sweet corn plants and/or card traps within the border and interior rows of sweet corn plots in both treatments. Furthermore, the percentage of sweet corn ears with herbivore feeding damage was similar in marigold diver-sified and monoculture sweet corn plots. Though marigold attracted some beneficial insects, it may not result in enhanced biological control of herbivorous pests in sweet corn plantings.