Mihail Garbuzov

Quantifying variation among garden plants in attractiveness to bees and other flower-visiting insects

1. Pollinating insects are globally declining, with one of the main causes being the loss of flowers. With the value of countryside reducing, urban areas, particularly gardens, are increasingly recognized as of benefit to wildlife, including flower-visiting insects. 2. Many gardeners specifically select plant varieties attractive to wildlife. Given the wide public interest, many lists of recommended varieties have been produced by both amateurs and professional organizations, but appear not to be well grounded in empirical data. These lists, however, are not without merit and are an obvious starting point. There is clearly a need to put the process onto a firmer footing based more on data and less on opinion and general experience. 3. We collected data over two summers by counting flower-visiting insects as they foraged on 32 popular summer-flowering garden plant varieties in a specially planted experimental garden, with two smaller additional gardens set up in year two to check the generality of the results. With many thousands of plant varieties available to gardeners in the United Kingdom, and other countries or regions, it would have been an impossible task to make a comprehensive survey resulting in a complete and authoritative list. 4. Our results are valuable and encouraging. Garden flowers attractive to the human eye vary enormously, approximately 100-fold, in their attractiveness to insects. Insects, especially bees and hover flies, can be attracted in large numbers with clear differences in the distribution of types attracted by different varieties. 5. Our results clearly show that there is a great scope for making gardens and parks more bee- and insect-friendly by plant selection. Horticulturally modified plant varieties created by plant breeding, including hybrids, are not necessarily less attractive to insects and in some cases are more attractive than their wild-type counterparts. Importantly, all the plants we compared were considered highly attractive to humans, given that they are widely sold as ornamental garden plants. 6. Helping insect pollinators in gardens does not involve extra cost or gardening effort, or loss of aesthetic attractiveness. Furthermore, the methods of quantifying insect-friendliness of plant varieties trialled in this study are relatively simple and can form the basis of further research, including ‘citizen science’.

Public approval plus more wildlife: twin benefits of reduced mowing of amenity grass in a suburban public park in Saltdean, UK

We examined the effects of reduced mowing on wildflower bloom and flower‐visiting insects in the Saltdean Oval, a 6 ha suburban public park in Saltdean, UK. In 2012, a novel management regime was initiated in which approximately half the grass area was left uncut, with the plan being to mow it once per year in autumn. In spring 2013, we set up four blocks, with each block subdivided into four 30 × 5 m strips treated under different mowing regimes: (a) regular mowing every 2 weeks all spring and summer, (b) regular mowing until 2 June, (c) regular mowing until 5 July, and (d) no mowing. The abundance of both flowers and flower‐visiting insects increased significantly with reduced mowing, being ca. 3 and 5 times greater in (d) than (a), respectively, with (b) and (c) intermediate. Mowing intensity, however, had a weak effect on wildflower species richness, which was only lower in (a). A 1 km bee, butterfly, and moth transect walk, 500 m within the long grass part of the park and 500 m within the short, recorded ca. 50× greater insect abundance in the long grass. A questionnaire of public opinion found that 97% of park visitors favoured encouraging insects and wildflowers. In terms of enjoyment of the park, 26% said that it had increased, 64% said that it stayed the same, and 10% said that it decreased. These results present an encouraging example of a potential win–win situation in urban land management change, where the interests of humans and wildlife are aligned, thereby making the goals of conservation easier to achieve.

Ivy: an underappreciated key resource to flower-visiting insects in autumn

Ivy (Hedera helix and H. hibernica) is a common autumn‐flowering plant found in Europe, North Africa, Macaronesia and Asia. Here, we use five complementary approaches (pollen trapping, nectar refractometry, local and regional surveys of insects foraging on ivy flowers, local survey of ivy abundance) to evaluate its importance to the honey bee (Apis mellifera) and other flower‐visiting insects in Sussex, England. Pollen trapping at six hives in two locations showed that an average 89% of pollen pellets collected by honey bees in the autumn were from ivy. Observations of foraging honey bees on ivy showed that ivy nectar is an even greater target than pollen, as 80% were collecting only nectar. Refractometry of samples from ivy flowers and from honey bees foraging on ivy showed that ivy nectar is rich in sugar, 49% w/w. Surveys showed that the main insect taxa foraging on ivy were honey bees (21%), bumble bees (Bombus spp., 3%), ivy bees (Colletes hederae, 3%), common wasps (Vespula vulgaris, 13%), hover flies (Syrphidae, 27%), other flies (29%) and butterflies (4%). The surveys also showed significant temporal and spatial variation in taxon abundance and proportion. A survey showed that ivy was very abundant on a small scale in both rural and urban areas, being present in 10/10 and 6/10 0.2 × 0.2 km samples within two 4 × 4 km areas respectively. The results show that ivy should probably be considered a keystone species with a high value in the conservation of flower‐visiting insects in autumn.

Longer tongues and swifter handling: why do more bumble bees (Bombus spp.) than honey bees (Apis mellifera) forage on lavender (Lavandula spp.)?

Lavender (Lavandula spp.) flowers attract more bumble bees (Bombus spp.) than honey bees (Apis mellifera). Counts of bees foraging on Lavandula × intermedia ‘Grosso’ at the University of Sussex campus, showed that bumble bees (92%) greatly outnumbered honey bees (8%). This was not due to a scarcity of honey bees, as the reverse ratio (94% honey bees vs. 6% bumble bees) occurred on borage (Borago officinalis) at the same location. Video analysis of free‐flying bees revealed that all bumble bee species present (Bombus terrestris/lucorum, Bombus pascuorum, and Bombus lapidarius) handled lavender flowers three times faster than honey bees (mean extraction times: 0.38, 0.37, 0.34 s respectively, vs. 1.30 s; all P < 0.001). Honey bee tongue length (6.6 mm) was approximately 2 mm shorter than those of bumble bees (7.8–8.9 mm) and 1 mm shorter than the lavender corolla tube (c. 7 mm). In addition, bumble bees probed twice as many lavender flowers encountered than honey bees (86% vs. 46%). Experimentally reducing effective corolla tube length with scalpel incisions significantly decreased extraction time for honey bees (from 1.11 to 0.76 s; P < 0.001) but not for bumble bees (0.33 to 0.28 s; P = 0.266). Results suggest that honey bees are deterred from foraging on lavender because they are being outcompeted by bumble bees, which forage more efficiently.

Data reliability in citizen science: learning curve and the effects of training method, volunteer background and experience on identification accuracy of insects visiting ivy flowers

• Citizen science, the involvement of volunteers in collecting of scientific data, can be a useful research tool. However, data collected by volunteers are often of lower quality than that collected by professional scientists. • We studied the accuracy with which volunteers identified insects visiting ivy (Hedera) flowers in Sussex, England. In the first experiment, we examined the effects of training method, volunteer background and prior experience. Fifty-three participants were trained for the same duration using one of three different methods (pamphlet, pamphlet + slide show, pamphlet + direct training). Almost immediately following training, we tested the ability of participants to identify live insects on ivy flowers to one of 10 taxonomic categories and recorded whether their identifications were correct or incorrect, without providing feedback. • The results showed that the type of training method had a significant effect on identification accuracy (P = 0.008). Participants identified 79.1% of insects correctly after using a one-page colour pamphlet, 85.6% correctly after using the pamphlet and viewing a slide show, and 94.3% correctly after using the pamphlet in combination with direct training in the field. • As direct training cannot be delivered remotely, in the following year we conducted a second experiment, in which a different sample of 26 volunteers received the pamphlet plus slide show training repeatedly three times. Moreover, in this experiment participants received c. 2 minutes of additional training material, either videos of insects or stills taken from the videos. Testing showed that identification accuracy increased from 88.6% to 91.3% to 97.5% across the three successive tests. We also found a borderline significant interaction between the type of additional material and the test number (P = 0.053), such that the video gave fewer errors than stills in the first two tests only. • The most common errors made by volunteers were misidentifications of honey bees and social wasps with their hover fly mimics. We also tested six experts who achieved nearly perfect accuracy (99.8%), which shows what is possible in practice. • Overall, our study shows that two or three sessions of remote training can be as good as one of direct training, even for relatively challenging taxonomic discriminations that include distinguishing models and mimics.

Survey of insect visitation of ornamental flowers in Southover Grange garden, Lewes, UK

Ornamental flowers commonly grown in urban gardens and parks can be of value to flower‐visiting insects. However, there is huge variation in the number of insects attracted among plant varieties. In this study, we quantified the insect attractiveness of 79 varieties in full bloom being grown in a public urban garden that is popular due to its beautiful flowers and other attractions. The results showed very clearly that most varieties (77%, n = 61) were either poorly attractive or completely unattractive to insect flower visitors. Several varieties (19%, n = 15) were moderately attractive, but very few (4%, n = 3) were highly attractive. Closer examination of Dahlia varieties showed that “open” flowered forms were approximately 20 times more attractive than “closed” flowered forms. These results strongly suggest that there is a great potential for making urban parks and gardens considerably more bee‐ and insect‐friendly by selecting appropriate varieties.

Using the British National Collection of Asters to Compare the Attractiveness of 228 Varieties to Flower-Visiting Insects

ABSTRACT Wildlife-friendly gardening practices can help conserve biodiversity in urban areas. These include growing ornamental plant varieties attractive to flower-visiting insects. Because varieties vary greatly in attractiveness, there is a need to quantify it in order to give objective advice to gardeners. Here, we used the British national collection of asters to compare the attractiveness of varieties to flower-visiting insects. We counted and identified insects as they foraged on flowers in 228 varieties growing in discrete patches that flowered during the survey period, 14 September–20 October 2012. In each variety, we also determined the overall capitulum size, the central disc floret area, and the ray floret color (blue, red, purple, or white). We also scored attributes relevant to gardening: attractiveness to humans, ease of cultivation, and availability in the United Kingdom. There was great variation among varieties in their attractiveness to insects, ranging from 0.0 to 15.2 per count per square meter, and highly skewed, with most being unattractive. A similar skew held for the two main insect categories, honey bees and hover flies, which comprised 28 and 64% of all insects, respectively. None of the floral traits or attributes relevant to gardening correlated significantly with attractiveness to insects. Our study shows the practicality of using a national collection for quantifying and comparing the attractiveness of ornamental varieties to flower-visiting insects. These results imply that choosing varieties carefully is likely to be of conservation benefit to flower-visiting insects, and that doing so is a no-cost option in terms of garden beauty and workload.

Most ornamental plants on sale in garden centres are unattractive to flower-visiting insects

Background Gardeners and park managers seeking to support biodiversity in urban areas often plant ornamentals attractive to flower-visiting insects. There is a huge diversity of garden plant varieties, and some recommendations are available as to which are attractive to insects. However, these are largely not based on rigorous empirical data. An important factor in consumer choice is the range of varieties available for purchase. In the UK, garden centres are a key link in the supply chain between growers and private gardens. This study is the first to determine the proportions of flowering ornamentals being sold that are attractive to flower-visiting insects. Methods We surveyed six garden centres in Sussex, UK, each over two days in 2015, by making 12 counts of insects visiting patches of each ornamental plant on display for sale that was in bloom. To provide a consistent baseline among different locations, we brought with us and surveyed marjoram (Origanum vulgare) plants in pots, which are known to be attractive to a wide range of flower-visiting insects. The attractiveness of plant varieties to insects was then expressed in two ways: the absolute number and relative to that on marjoram (‘marjoram score’), both per unit area of plant cover. In addition, we noted whether each variety was recommended as pollinator-friendly either via a symbol on the label, or by being included in the Royal Horticultural Society’s ‘Perfect for Pollinators’ list. Furthermore, we compared the attractiveness of plants that are typically grown for more than one year versus only one year. Results We surveyed 59–74 plant varieties in bloom across the six garden centres. In each garden centre, the distributions of variety attractiveness were highly skewed to the right, with most varieties being relatively unattractive, and few varieties highly attractive to flower-visiting insects. The median attractiveness of varieties with a recommendation was 4.2× higher than that of varieties without. But, due to the large variation there was a substantial number of both poor varieties that had a recommendation and good varieties that did not. Median attractiveness of multi-year plants was 1.6× that of single-year plants, with a similar overlap in distributions. Discussion Our study demonstrates the practicality of carrying out plant surveys in garden centres. Garden centres display large numbers of varieties for sale, most of which are in bloom. Furthermore, data gathered in garden centres appear to correlate well with data gathered in two previous studies in Sussex for plants established in gardens. Although it is unclear whether the varieties being sold in garden centres are a fair representation of varieties that are actually grown by gardeners, our results suggest that there might be considerable scope for making parks and gardens considerably more insect-friendly through judicious variety choices.

Lattice fence and hedge barriers around an apiary increase honey bee flight height and decrease stings to people nearby

Summary Urban beekeeping is becoming more popular in the UK. One of the challenges faced by urban beekeepers is finding a suitable apiary location. Honey bees are often perceived as a nuisance, mainly due to their stinging behaviour. Here, we experimentally test the assumption that barriers around an apiary such as walls or fences, force the bees to fly above human height, thereby reducing collisions with people and, consequently, stinging. The experiment was conducted in two apiaries using two common types of barrier: a lattice fence (trellis) and hedge. Barriers were 2 m high, which is taller than > 99% of humans and is also the maximum height allowed by UK planning regulations for garden fences or walls. We found that barriers were effective at both raising the mean honey bee flight height and reducing stinging. However, the effects were only seen when the barrier had been in place for a few days, not immediately after the barrier was put in place. Although this raises interesting questions regarding honey bee navigation and memory, it is not a problem for beekeepers, as any barrier placed around an apiary will be permanent. The effect of the barriers on raising bee flight height to a mean of c. 2.2–2.5 m was somewhat weak and inconsistent, probably because the bees flew high, mean of c. 1.6–2.0 m, even in the absence of a barrier. As barriers can also reduce wind exposure, improve security and are inexpensive, we recommend their use around urban apiaries in places such as private gardens or allotments, where nuisance to humans is likely to be a problem.