Can Plants Hear Bees?

Whenever I encounter evening primrose plants in bloom, I watch them for a while. These native plants attract a variety of bees and other pollinators. At night, evening primrose is highly attractive to large moths. In the early hours of the morning, fast flying blue orchard bees visit the yellow flowers. Later in the day, butterflies, honey bees, flies, and other insects actively forage evening primrose. In today’s photo a honey bee collects nectar from evening primrose.

Honey bees can detect differences in nectar sugar concentrations of one to three percent, and foraging worker bees seek those nectar sources with the greatest concentrations of sugars. Lilach Hadany, a researcher at Tel Aviv University, questioned whether plants could hear sounds similarly to animals, https://www.nationalgeographic.com/science/2019/01/flowers-can-hear-bees-and-make-their-nectar-sweeter/. Hadany’s findings reveal that at least one plant, evening primrose, responds to the vibrations of pollinators’ wings. Within minutes of exposure to vibrations in the range of honey bee wing beats (0.2 to 0.5 kilohertz), evening primrose increased the concentration of sugars in its nectar. Hadany’s lab found that within three minutes of exposure to honey bee wing-beat-frequency vibrations the plants increased the nectar sugar concentrations from between 12 and 17 percent to 20 percent. In field observations, her researchers found pollinators around evening primrose plants nine times more frequently after the plants were visited within the past six minutes. The resulting sweeter nectar is naturally more attractive to bees and other pollinators. Since flowering plants, such as evening primrose, depend upon insect pollination for reproduction, any plant that attracts more pollinators has a reproductive advantage. Evening primrose flower petals are shaped like an open bowl. Such shapes concentrate and increase vibrations. The researchers at the Tel Aviv lab found that evening primrose flowers concentrated vibrations of the frequency range of honey bees. The ability of a flowering plant to increase its nectar’s sugar concentration would make it more attractive to pollinators and more likely to be pollinated, the first step in the plant’s reproduction.

--Richard

First Frost

The temperature dropped below the freezing point last night for the first frost of the fall. With very normal seasonal weather, the air had warmed considerably by mid-morning; and the honey bees were flying. A number of the bees were eagerly foraging evening primrose plants that were slightly wilted by the overnight frost. This is the first day that I have noticed honey bees foraging evening primrose in any numbers. More often, I have found moths, butterflies, blue orchard bees, and other solitary bees foraging this hearty native plant. The evening primroses have been in continuous bloom for several months. During the summer I observed luna moths the size of small birds pollinating the evening primrose flowers at night. The change in the honey bees’ foraging behavior seems to have followed the change in the weather. The frost may have caused the plants that the bees were foraging the previous day to stop producing nectar. Honey bees will forage a species of plants as long as the nectar is reliable, then, they will scout for a different nectar source.

With the season’s first frost foretelling more cool and cold weather to come, the honey bees are reacting to a scarcity of available nectar. They are searching for new sources. Many bees are flying around the wood shop where I am cleaning hive frames. There is also much activity on the landing boards of bee hives where the guard bees are checking all returning bees to prevent robbers from entering. Each hive’s winter stores of honey are vulnerable to robbing bees. Evening primrose is a medicinal herb that was a staple food for many Native American tribes. The colorful and long-blooming evening primrose is often planted as a hearty summer flower along fencerows and in meadows.
--Richard

Evening Primrose in Bloom

The evening primrose is a nighttime blooming wildflower. While I have observed it being worked at dawn by honey bees foraging for pollen, it primarily attracts other pollinators. I have seen flies, moths, butterflies, and solitary bees working evening primrose early in the morning. Luna moths, the size of small birds, work the flowers at night. Click on the picture to see a blue orchard bee foraging for pollen in an evening primrose blossom. The fast flying and gentle blue orchard bee strikes the flower hard and then scrubs its body around inside of the blossom. Its active movement inside the flower makes the blue orchard bee an effective pollinator. The native blue orchard bee carries its load of pollen on hairs on the lower side of the bee’s abdomen.

The current research program that the USDA is funding to study bee health involves both honey bees and other pollinators. Bees that are not honey bees, called non-apis bees, are being established in managed arrangements at each of the seven bee yard locations in the nation-wide study. The purpose of this study of these non-apis bees is to determine if there are cross infections between the species. Bumble bees are being sampled to check for stress and, hopefully, increase efficiency of their use as pollinators. The investigators are also studying the effects of the neonicitinoid pesticides, like Imidacloprid, on the non-apis bees. They are looking into the sub-lethal effects of these pesticides and any effects caused by their residues. The non-apis bees, like the blue orchard bee, serve an important role in helping to pollinate flowering plants. They help the honey bee complete the pollination required to produce fruit and seeds for wildlife and humans.
--Richard