Natural enemy and herbivore response to the inclusion of floral resources in intermountain west alfalfa systems

Alfalfa weevil is the most problematic pest for Wyoming hay producers. Current methods of control, namely chemical control and early harvest, can be costly and inefficient. Improving the effectiveness of natural enemies as biological control agents can reduce farmer reliance on chemical controls and risk of yield loss. We determined how incorporation of floral resources in intermountain west alfalfa fields affected abundances of natural enemies and pests in crop and floral habitats.  In 2014, we established a field experiment comprised of 25m-sq alfalfa plots, adjacent to either annual flower strips, native perennial flower strips, or fescue grass, our control. This was the establishment year, thus not all perennial flower species bloomed and insect sampling began later in the season due to delayed bloom and alfalfa growth.

We used vacuum sampling to collect insects in all habitat types. The generalist predators Nabidae preferred alfalfa over either of the flower strips or control (grass buffer). Conversely, lady beetles were more abundant in the flower strips than the alfalfa or grass habitats. Alfalfa weevil adults were found in alfalfa, but not in the other habitats. No weevil larvae were found in 2014 given that alfalfa weevil is an early season pest, and the alfalfa was spring-seeded. The data from this experiment demonstrate that arthropod groups respond to habitat types differently and may have preferences. This study will be repeated for the duration of the 2015 growing season, to continue to evaluate arthropod habitat preferences as the perennial species mature.