Pollen nutrient content, insect visitation, and morphological characteristics of warm-season turfgrasses

Authors: Harris-Shultz, Karen; Corby-Harris, Vanessa; Hoffman, Gloria; Snyder, Lucy; Watkins De Jong, Emily; O'Hearn, Jonathan; Read, Quentin; CLEM, CARL - Illinois State University

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pollinators are decreasing globally and to help struggling pollinator populations, people are encouraged to plant nectar-rich plants. Grasses, which usually only provide pollen, are rarely recommended and yet a wide range of insects, especially bees and hover flies, use grass pollen as a food source. In this study, the pollen nutrient content was examined for three popular warm-season turfgrasses and insects that were consuming or collecting pollen were recorded over a four-week period with three mowing intervals. Pearl millet (a grass used for forage and grain) pollen was 12.10% protein and 6.38% lipid, zoysiagrass pollen was 5.48% protein and 6.25% lipid, and centipedegrass pollen was 4.22% protein and 4.25% lipid. We were unable to obtain sufficient amounts of pollen from ‘Celebration’ bermudagrass for nutrient content analysis. Bombus impatiens (bumblebees) were observed collecting centipedegrass pollen while hover flies were observed consuming bermudagrass, centipedegrass, and zoysiagrass pollen. During the four-week observation period for plots mowed every two or three weeks, centipedegrass and zoysiagrass had higher flowering than bermudagrass. Thus, insects utilize turfgrass pollen despite the low protein and lipid contents.

Technical Abstract: Bees and hover flies have been observed collecting/consuming pollen from grasses including turfgrasses. Yet, little is known about the nutrient content of turfgrass pollen nor the insect visitation frequencies to these plants. In this study, we sought to examine the protein and lipid content of three commonly used warm-season turfgrasses: zoysiagrass (Zoysia spp. Willd.), centipedegrass (Eremochloa ophiuroides (Munro)), and bermudagrass, Cynodon dactylon (L.) Pers. We also report insect visitation to the inflorescences of these grasses observed over a four-week period with three mowing frequencies. Our goal was to determine if insects visit certain turfgrasses more frequently, and if mowing intensity impacts their visitation. Zoysiagrass pollen was 5.48% protein and 6.25% lipid, centipedegrass pollen was 4.22% protein and 4.25% lipid whereas pearl millet (Cenchrus americanus L.) pollen was significantly higher at 12.10% protein and 6.38% lipid. We were unable to obtain sufficient pollen from bermudagrass for nutrient content analysis. Overall, visitation by bees was low. We recorded only 7 instances of bumble bee (Bombus impatiens Cresson) visitation to centipedegrass pollen and no visits to the other turfgrass species. In contrast, hover flies (Syrphidae), especially of the genera Toxomerus were observed visiting inflorescences of all 3 turfgrasses. During the 4-week observation period for plots mowed every 2 or 3 weeks, centipedegrass and zoysiagrass had higher flowering than bermudagrass. Additionally, for plots mowed every 2 or 3 weeks, bermudagrass had higher chlorophyll content than centipedegrass and zoysiagrass whereas centipedegrass had higher peduncle and spike lengths than bermudagrass and zoysiagrass. Thus, for this study, the protein content of centipedegrass and zoysiagrass was lower than pearl millet and the presence of hover flies was not impacted by grass species or mowing frequency.