Research at Tifton helps determine the benefits of turf grass for bees

TIFTON – A USDA Agricultural Research Service researcher has found surprising benefits of turfgrass for bees.

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Did you know that the grass in your garden can serve as a food source for pollinators? Dr. Karen Harris Schultz, a research geneticist at the USDA Agricultural Research Service in Tifton, Georgia, is leading the charge in discovering that many grasses, even some grasses, can serve as a pollen food source for bees and hoverflies. Her findings are groundbreaking and could change the way we think about our lawns.

Harris-Schultz’s research shows that grasses provide a wealth of resources for bees and other pollinators. This means homeowners can take steps to make their yards more pollinator-friendly simply by changing their mowing habits and reducing their use of pesticides.

“Anytime you can provide data to show the ecosystem services a turfgrass provides, it benefits the turfgrass industry,” she explains. With thousands of bees collecting pollen from the inflorescences (or grass flower head) of centipede grass alone, it is clear that the benefits are significant.

So, next time you look at your garden, remember that it’s not just a pretty sight – it’s a vital part of our ecosystem.

“Our research results show that grasses can serve as a food source for pollinators. I find this very exciting and that homeowners can observe bees directly in their yards,” she said.

Harris Schultz has heard about grassy weeds referred to as “biological wastelands” that provide no resources for bees at seminars and on social media for years. Weeds are often dismissed as self- and primarily wind-pollinated without the use of bees. But that was actually quite the opposite of what she saw in her garden and in her friends’ garden. She recalls a particular memory of walking on an acre of centipede grass and seeing thousands of honeybees collecting pollen from inflorescences.

“The sound of all the bees buzzing was amazing. I started paying more attention to bees on warm-season grasses after that, and I realized that this would be an exciting avenue of research, and I recruited University of Georgia entomologist Shimat Joseph and physiologist David Jespersen on our first project together.”

Recent research conducted in Tifton and Griffin, Georgia

In their first study to address whether grassland meadows are “biological wastelands,” Joseph and Harris Schultz and Jespersen found that 13 different genera of bees were present in centennial grassland meadows in central and southern Georgia. The most common bees were sweat bees (of the genera Lasioglossum and Augochlorella), bees of the genus Halictus, long-horned bees, and bumblebees. Sweat bees of the genus Lasioglossum were captured most often (137 of 173 collected). Many of the bees found were ground-nesting bees.

The second project, led by Joseph, examined what pollinators directly consume or collect pollen from centipede inflorescences. The setup consisted of 11 central Georgia centipede grasses, mowed every 14 days, and sampled 12-13 days after mowing. The study observed that pollinators collect or consume pollen on inflorescences between 9:30 a.m. and 1 p.m. Seven insect species were found consuming or collecting grass pollen, with the most common insects being hoverflies, sweat bees (genera Lasioglossum), bumblebees, and honeybees.

From both studies, bees are found in grass meadows, and hoverflies and bees feed on grass pollen. Harris Schultz encouraged caution when using pesticides that affect bees and hoverflies on centipede lawns, and if you want pollinators to feed on your garden, don’t cut flowers when your garden is actively flowering. Make sure to mow the grass as soon as it blooms to create new flowers, otherwise the grass will start producing seeds instead of flowers.

Centipede flowers from the top of the inflorescence to the bottom (Figure 2). Anthers are key here. They contain pollen. If you look at the cannabis seed heads in your garden and the anthers look healthy or are just starting to flower, don’t mow. If the seed heads have anthers and are completely dry, it’s time to cut.

Jonathan O’Hearn, an entomologist, recently joined USDA-ARS in Tifton and is interested in grass-feeding bees. Their experiment planned for spring 2023 is to answer the question: “How do mowing frequency, irrigation and fertility affect pollinators collecting pollen from Celebration® Bermudagrass, centipedegrass (common) and EMPIRE® Zoysia.”

Harris-Schultz explained that they hope to have 2-3 years of data from the summer 2023 experiment. She hopes that once we know which grasses provide a food source for bees, people will start to notice them more on grasses. An estimated 75% of the world’s flowering plants and 90% of the world’s food crops depend on pollinators for reproduction, yet pollinator numbers have been declining worldwide for several decades, she said. She also explained that bees and hoverflies have been documented to consume pollen from about 100 grass species, but these interactions are often overlooked and not studied. “The grasses serve as a food source for the bees,” she said. Just by looking at warm-season grasses, bees have been observed collecting pollen from centipedes, bermudagrass (the common type, not the pollen of the sterile hybrids) and bahia grass.

Genetic analysis of grass and background

Harris Schultz has been at the forefront of DNA research in grass as well. When I started in Tifton, there were few genetic markers available for turfgrass. She created the first sets of microsatellite markers (small, repeating pieces of DNA) for bermudagrass and centipedes, and over the years there have been many improvements in genetic and phenotyping techniques, she said.

“For grass genotyping, I look at the DNA using markers that are typically microsatellite markers,” Harris-Schultz said. Labeling and flow cytometry are very useful for identifying a myriad of stakeholder issues. Over the years, it has genotyped nearly 1,500 samples obtained from turf producers, golf courses, researchers, etc. to determine what varieties they have, identify contaminants, or determine genetic relationships.

Harris-Schultz says she has loved plants since she was young, and over the past 10 years, her interests have expanded to include insects. She explained that her experiences in college and university programs exposed her to biological research.

“After graduating from the University of Tennessee with a major in biology with an emphasis in ecology, evolution, biochemistry and cell biology, I thought my favorite things were plants and biochemistry,” Harris-Schultz said. “I applied to several graduate programs, visited campus and faculty, and felt at home in the Department of Biochemistry at Texas A&M.”

Harris-Schultz looks forward to continuing her research on pollinators and turfgrass.