Report of March meeting 2019 – A talk by Brigit Strawbridge

Bees: Importance of diversity and relationships with flowering plants

Brigit began by saying she intended covering ALL bees, not just honey bees, as well as other pollinators, in order to show the importance of diversity in plant ↔ bee relationships.

To put things in perspective there are roughly:

320,000 flowering plant species worldwide,

more than 300,000 pollinating animal species

and 25,000 bee species.

In the UK our pollinators include:

59 butterfly species,

2,500 moths,

7,000 flies,

9,000 wasps,

4,000 beetles and

270 species of bees.

‘Indicator Species’

The importance of bees became apparent when Brigit explained that about a third of our food and beverage producing plants are pollinated by bees and that up to 80% of flowering plants are dependent on bees for reproduction. No wonder that bees are regarded as a key ‘indicator species’. The knock on effect of anything affecting bees will soon be felt in the rest of the environment.

What is a bee?

From Brigit’s photos we learned that bees range in size from Wallace’s giant bee (Megachile pluto), about 38mm long, to a tiny solitary bee the size of a midge! Worker bumble bees in the UK can be up to 24mm.

Briefly, the life cycle of a bumble bee starts with the emergence of the fertilised queen in the spring. She feeds on nectar and starts building a nest. She provides pollen and nectar for the developing young workers who will take over the duties of colony maintenance, leaving the queen free to concentrate on egg laying. Later in the year the queen lays drone eggs instead of worker eggs, followed by fertile female eggs. The males leave the nest and move to other areas while the queens mate and find a crevice to hibernate over winter.

Bee decline

Causes of bee decline in recent years can be largely attributed to habitat loss and pesticides. Further damage is being caused by climate change, invasion by non-native species and pollution. All of these effects reduce biodiversity and the ability of ecosystems to survive and thrive.

Cross pollination

Cross pollination is the key to diversity of the flowering plants which have been evolving alongside the insect world for the last few tens of millions of years. So we see a range of characteristics in bees enabling them to take advantage of the numerous niches in the plant world. UK bumble bees, for example, have a proboscis length of 15-20mm whereas the honey bee proboscis is only 6mm.

Pollen collection methods vary between species. We are familiar with the pollen baskets of honey bees but red mason bees will ‘buzz’ on a flower to dislodge pollen, which sticks to the hairs on its abdomen, called the scope. Sometimes, if the proboscis is not long enough, buff tailed bumble bees will cut a hole in the corolla to reach nectar and pollen, a process called larceny.

Biodiversity facts

98% of wild flower meadows have disappeared in the last century.

Neonicotinoids persist in the environment and pass into the soil and water courses. From here they are reabsorbed into plants, pass into nectar and pollen, and end up affecting pollinators. The toxic mix of pesticides and fungicides affects the ability of bees to ferment bee bread which is essential to their existence.

What can we do?

• Don’t tidy your garden too much. Leave heaps of ‘rubbish’ for bees to nest in.
• Make or buy ‘Bee Hotels’. Keep them clean.
• Plant for a succession of flowering plants all through the year. Brigit’s list plus a few extras – mahonia, crocus, aconite, celandine, snowdrops, hellebores, dandelion, flowering currant, pulmonaria, vipers bugloss, nepeta, borage, wild marjoram, Michaelmas daisies, sedum, ivy, heathers.
  Don’t forget the trees and shrubs – viburnum , mimosa, camellias, sarcococca, skimmia.
• Plant wild flower seed mixes for meadows if you have room.

Recommended reference books:

Field Guide to the Bees of Great Britain and Ireland – Steven Falk

Plants for Bees – Kirk and Howes (available to East Devon members from the branch library)

* All images © Brigit Strawbridge

Report of February meeting 2019

Chronic Bee Paralysis Virus (CBPV) – A talk by Clare Densley, Manager of Buckfast Abbey Apiaries

What is CBPV?
CBPV mainly attacks adult bees and causes two forms of ‘‘paralysis’’ symptoms. The most common form is characterised by an abnormal trembling of the body and wings, an inability to fly leading to crawling on the ground, bloated abdomens, and dislocated wings. The other form is identified by the presence of hairless, shiny black bees that are attacked and rejected by guard bees at the entrance to the colony. Both forms of symptoms can be seen in bees from the same colony.

Diagnosis of CBPV

The virus multiplies to millions within the bee affecting most organs with little chance of the individual bee surviving. In addition to the signs above you may find, on the top bars, slow, slightly shaky bees which do not react to smoke.
Check all the symptoms before deciding the cause of dead bees inside and/or outside the hive. Do not assume that many dead bees means pesticide poisoning. CBPV is, as its name suggests, a chronic problem. Not all bees will die at once, stress can accelerate the spread of infection or improving conditions can cause it to clear up.

In Clare’s experience queens often seems to remain unaffected and can carry on laying as long as they are well fed. This has also been noted by Giles Budge. Advice from older books and the NBU suggest re-queening with a queen from a less susceptible strain of bee. Clare found that re-queening made no difference to a colony which was suffering badly. Also removing a queen from an infected colony and introducing her to a healthy colony did not cause disease to develop.

What is a virus?

A virus is a small infectious agent that replicates only inside the living cells of other organisms. Viruses are basically parasites. They invade an organism, take over their cells and turn them into factories for producing more viruses. There are 23+ viruses that affect honey bees. Viruses normally range from 30 to 100 nanometres (1 nanometre = 1 millionth of a millimetre).

How does CBPV infect bees?
Infection often initiates when the colony is stressed (overcrowding, nutritional stress, but not via varroa infestation). Usually passed from bee to bee with a few virus particles entering the cuticle where hairs are broken off. By comparison, transmission by feeding requires hundreds of virus particles.

CBPV can also infect some ant species which act as a reservoir in the wild.

Drifting has been implicated in spreading the disease between colonies.

How does the virus act?
Infected bees contain millions of viral particles, half of which concentrate in the head causing the symptoms associated with the nervous system. Many more accumulate in the hind gut adding to viral load inside the hive.

‘Good’ gut bacteria are important in bee health, helping to fight pathogens by blocking entry into bee cells. Good nutrition is therefore essential for fighting the disease.

Treating CBPV

The NBU recommends that in strong colonies showing signs of CBPV, beekeepers ensure there is plenty of room by adding supers or an extra brood box and also that colonies are well fed.

Clare doses the bees with Varromed (formally Hive Clean) right from the outset. This seems to activate not only the grooming process but also seems to encourage the bees to clear out their dead.

Infected colonies may be short of readily available food due to a lack of foragers and will benefit from feeding direct to the comb in the brood area. Spray or pour liquid feed onto an empty brood frame and put it next to brood. Dribble syrup onto the bees as well. These methods work better than feeders.

Clare uses garlic powder and probiotic capsule powder added to the syrup which prompts an immediate feeding response. See below for Clare’s recipes for a Fondant Recipe for Bees and a Garlic Syrup for Bees

Clean up dead bees inside and outside the hive.

Don’t overcrowd your apiaries. If hives are badly infected, set up a new apiary and move the affected hives.

Practice good apiary hygiene.

* Images courtesy of The Animal and Plant Health Agency (APHA), Crown Copyright

With thanks to Clare Densley for sharing her recipes for use in combating CBPV.