A New, Colorful Way to Attract Pollinators to Crops
By Andrew Porterfield
Intensive agriculture practices often depend on pollinators for success, but these practices also tend to eliminate the plants that are popular among bees, wasps, and other pollinators. Farmers and scientists have looked at planting wildflowers in growing areas, but a team from the University of Wyoming looked at an alternative source of attraction: specialty cut flowers.
These flowers—marigolds, zinnias, strawflower, and others that are grown only during a short season—could produce a win-win situation for growers. They could attract a wide diversity of pollinators and provide supplemental economic benefits to farmers. Most specialty cut flowers in the U.S. are imported from near-equatorial countries, but growing them here could provide an alternative to imports.
But do they attract pollinators? And how much? Little research had been done on specialty cut flowers and pollination. Until now, that is. A team of entomologists and horticulturalists at University of Wyoming (UW) headed by graduate student Samantha Nobes found that planting several species of specialty cut flowers in “high tunnel” shelters did indeed attract a wide variety of pollinating insects. Their results are reported in an article published last week in the Journal of Economic Entomology.
The high-tunnel experiments were also significant because they showed that insects visited the flowers inside the structures, which have sides that can be rolled up in good weather to open access to flowers. (The structures also protect plants from high winds, frost, and large swings in temperature from day to night, common in high-altitude locations like Laramie, Wyoming.)
The researchers planted the flowers in two high tunnels at about 7,200 feet above sea level. Sides were opened when temperatures reached above 40 degrees Fahrenheit. Six flower species were raised in the spring and summer: cultivars of marigold, stock, strawflower, ornamental carrot, cockscomb, and zinnia. Eighteen plots of flowers were planted in total. The group then measured the types and numbers of insects visiting each.
The flowers attracted a diverse group of pollinators. These included members of Diptera (flies), Hymenoptera (bees and wasps), Coleoptera (beetles), and Lepidoptera (butterflies and moths). Flies visited flowers most often (45 percent of visits), followed by bees and wasps, and, more distantly, beetles, butterflies, and moths.
Bees (mostly Bombus species) most often visited marigolds, strawflowers, and silver cock’s comb. Wasp visits did not vary much among the flower species, but wasp family preferences were distinct. Ten unique wasp families were identified.
The study yielded some unexpected results. “We were pleasantly surprised to observe the diversity of insects visiting these specialty cut flowers,” says Randa Jabbour, Ph.D., associate professor of agroecology at UW and senior author on the study. “Although many entomologists are interested in the best ways to provide floral resources to bees, ornamentals or cut flowers are rarely considered as a possible avenue to accomplish this goal. … Our collaboration between entomologists and horticulturalists allowed us to take an innovative approach to consider insect conservation alongside potentially marketable flower production.”
While the high tunnels are useful to high-altitude areas like Laramie, other types of structures could also be used to cultivate flowers and attract pollinators, as long as there is easy access from the outside. Year-round greenhouses, for instance, are always closed, and pollinators are rarely seen in them (unless they were introduced there).
The diversity of pollinators was also seen as good news. Syrphid and non-syrphid flies provide both pollination (as adults) and pest control (as larvae). Non-bees may be less effective at depositing pollen for each flower visit, but they visit flowers more often than do bees. Certain wasps, such as crabronids, sphecids, and vespids, are good “back up” pollinators (compared to bees) and are predators to plant pests.
Many species of cut flowers can be used to attract pollinators (as well as horticultural income streams), but these plants must be handled very carefully at each stage of production. There may be tradeoffs between harvesting and providing resources to bees and other pollinators—which the team recommended as a future avenue of research.
Journal of Economic Entomology
Andrew Porterfield is a writer, editor, and communications consultant for academic institutions, companies, and nonprofits in the life sciences. He is based in Camarillo, California. Follow him on Twitter at @AMPorterfield or visit his Facebook page.