Effects of pollinators and head feeding insects on sunflower (Helianthus annuus L.) fitness

Flowering sunflower (Helianthus annuus L.) is attractive to insect pollinators and herbivores that affect yield and seed quality traits. Insecticide applications made during anthesis can reduce insect damage to seeds but can also harm bees and decrease the benefits of cross-pollination. The objective of this study was to measure the relative positive and negative contributions of bees and seed feeding insects to yield and seed quality traits. Yield and seed quality traits were compared in all combinations of exposure to natural populations of bees and seed feeding insects. Plants in the Bees & No Pests group produced the highest yield, and plants in the No Bees & Pests group generally produced the lowest yield. Plants in the No Bees & No Pests and the Bees & Pests groups were intermediate in seed production. For plants in the Bees group, high numbers of small seeds were produced. In some instances, germination rates and seed oil percentages were increased by the presence of bees and decreased by the presence of pests. The results indicate that use of an insecticide to manage pest insects may not result in maximized seed production if bee cross-pollination is reduced. Insect management in sunflower should consider impacts on both wild and domesticated bee populations. Managing sunflower to maximize bee activity may be more valuable than controlling pest insects in some environments.