Open Agriculture. 2019; 4: 676-683. by Maria C.-Y. Leung*, Jessica R.K. Forrest
Everyone who has ever grown haskaps (honeyberries) knows that they attract bumble bees. In Fairbanks, they bloom so early, and air temperatures can be cool, that honeybees can be insufficient for good berry production. Researchers Maria Leung and Jessica Forrest showed that bumble bees rule the day. The authors also reported that commercial berry production Yukon doubled from 2011 and 2016, and the most prevalent berry crop is haskap.
Haskaps are self incompatible and require two compatible cultivars for pollination. and they attract a variety of insects including bee flies, syrphid flies, honeybees, butterflies and bumblebees. The researchers counted and identified insect visitors in commercial fields between 11 am and 5 pm on cool, sunny days near Whitehorse, Yukon Territory. Bumble bee visitors ranged from 96% to 32% of all insect visitors. Despite the flower architecture which is trumpet shaped and would hint at butterflies, they were the least common insect visitors. Native insect are very important to pollination in the North. The authors contrasted their results with Saskatchewan where honey bees outnumbered bumble bees as insect visitors on hasps. Anyone who gardens in the North should promote nesting sites for native bumble bees.
Abstract: Recently, the Yukon has seen a large growth in agricultural activity. Crops of commercial interest for local consumption and the export market include domestic berries, especially haskap (Lonicera caerulea L.). However, information on the pollination of these crops in our northern climate is lacking. To begin addressing this knowledge gap, we characterized foraging habits of on-farm bees in southwest Yukon by: 1) identifying pollen collected by bees occupying solitary bee houses; and 2) identifying and counting insect visitors to haskap flowers. Results show that cavity-nesting bees collect a wide variety of pollen including pollen from haskap, and that bumble bees (Bombus spp.) were much more common on haskap flowers than domestic honey bees (Apis mellifera L.), other bee species, syrphid flies, and butterflies. The number of bumble bees per haskap flower was also higher than reported elsewhere in Canada. The ability of bumble bees to be active in cool temperatures and the proximity of the study farms to natural ecosystems likely explain the prevalence of bumble bees in this study. In Yukon, it is still possible to support insect pollinators by maintaining natural areas among agricultural lands. Such undeveloped lands are, at present, typical of agricultural landscapes in subarctic Canada.
Two Prolonged Bee Visits Suffice to Maximize Drupelet Set for Red Raspberry by Corey J. Andrikopoulos and James H. Cane, Utah State University, Logan, HORTSCIENCE 53(10):1404–1406. 2018. https://doi.org/10.21273/HORTSCI13124-18
Everyone knows that insect pollination is critical for fruit set in many commercial berry species. The red raspberry is no exception. It produces an aggregate fruit composed of individual drupelet fruits. If the weather is bad, the insects are not flying, or something else interrupts pollination, you can easily get misshapen fruit and lower yields. Researchers at Utah State found that it only takes two prolonged visits of 1 minute or more to get great fruit set. You don’t need hundreds of bees visiting the flowers. Here are a few tidbits about red raspberries from this article:
- Red raspberries are mostly self fertile but because the pollen bearing anthers are not located directly adjacent to the female stigmas, self pollination can be spotty.
- A single flower bears 60 – 90 stamens with ample pollen, but bees and other insects are needed to move the pollen to the central region of female stigmas. Each individual stigma needs to be pollinated to get a good fruit.
- Previously scientists estimated that up to 68 visits per flower were necessary to get adequate fruit set, but these authors showed that 2 visits were great.
- For two visits to be adequate, the bee must really work the flower for a prolonged period of time (up to a minute or more). Bees often spend long times on a newly opened flower first thing in the morning because that’s when nectar flow is at its peak after a night time of storing up nectar in the flower’s nectar pool.
- Individual flowers remain receptive for about 2 days, and every morning the nectar pool is recharged. Nectar release is temperature dependent.
- By individually covering flowers as they bloomed and comparing them to uncovered controls, the researchers showed that bee visits increased drupelet formation by 2 to 4 times. If a flower was visited first thing in the day for a prolonged period, two such visits would be sufficient to have great fruit formation.
- There is also a condition of over visitation where bees actually damage the female stigmas if there are too many of them working the flowers.
Adding honey bee hives to a raspberry garden is a good idea for most commercial businesses. However, Alaska temperatures, especially in the a.m. can be cold – too cold for honey bees to be very active. Since nectar flow is greatest first thing in the morning, wild bumble bees become even more critical for great fruit set in northern gardens.
This is a summary of Rehanon Pampel’s thesis documenting bumble bees in agricultural areas of the Interior. It documents species as well as seasonal occurrence. You think bumbles are doing their thing all summer, but there is a definite seasonal pattern to their work.
Here is a link to a journal article comparing native and non-native pollinators of Haskap. They concluded that native bumble bees (compared to orchard bees and honey bees) have the highest pollen deposition per visit, visited the most flowers in a given period of time and could fly at the coldest temperatures, making them the most suited for successful pollination at least in cooler springs. Another interesting thing to note is Figure 1c in the paper. It shows a fruit in which the bracteoles have not fused around the two ovaries of the paired flowers. I find this interesting because I observed several fruits shaped like this and wondered what caused it. Understanding the biology of the flower, the formation makes more sense! KD Fairbanks
Frier, S.D, C.M. Somers and C.S. Sheffield. 2016. Comparing the performance of native and managed pollinators of Haskap (Lonicera caerulea: Caprifoliaceae), an emerging fruit crop. Agriculture, Ecosystems and Environment 219:42-48.
It was all over the internet recently, bumble bees were put on the endangered species list. Research into this decision told me that the “rust-patched” bumblebee (Bombus affinis) was the pollinator. According to the U.S. Fish and Wildlife Service, the bee can be found in the eastern portion of the United States and in some parts of Canada. The Alaskan Department of Fish and Game cites Bombus polaris, the Arctic bumblebee, in this article describing the life of a bumble bee in Alaska. Because they are important pollinators, this is of horticultural interest. The article can be found here:
Sutton, A. n.d. A brief busy life of the arctic bumblebee. Available online: Bumble bees
U.S> Fish and Wildlife Service. 2016. Rusty Patched Bumble Bee. Available online: Rusty patched
. Accessed 5 Oct, 2016
The Leonard Lab at The University of Nevada Reno has been conducting some neat experiments on pollination. Here is a link to a write up of one study showing bumble bee recognition of flower color in association with pollen rewards. They are such smart creatures! Bumble bee learning
If you’re a gardener, berry lover, or if you eat food, it wouldn’t hurt to spend a little more time appreciating our pollinators. One of my favorite authors, Rowan Jacobsen, wrote an enlightening book on the topic of pollination–Fruitless Fall (see below), in particular, on colony collapse disorder in honeybees. It’s frightening to think about the fragility of our current system of pollination. Luckily, wild berries in Alaska do not depend on managed hives for pollination. On my reading list since I read Fruitless Fall is Forgotten pollinators. We should probably all spend a little more time appreciating these flying wonders. I enjoyed watching the beautiful video of buzz pollination(see below) And while we’re on the topic, check out the Xerces society. They have a plethora of great resources on protecting and appreciating our sometimes forgotten and under-appreciated invertebrates. HR Fairbanks
Buchman, S. L. 1997. Forgotten pollinators. Island Press.
Jacobsen, R. 2010. Fruitless Fall: The Collapse of the Honey Bee and the Coming Agricultural Crisis. Bloomsbury, USA.
Xerces Society for Invertebrate Conservation (Home Page). 2016. Available at: http://www.xerces.org.
14 Sept, 2016.