Blog - Pests & Diseases
Food for thought?
It is estimated that each year UK households spend some 250 million pounds on bird food. This amounts to some 150,000 tonnes of suet pellets, fats balls, peanuts, sunflower seeds etc - on offer (in feeders of varying complexity*) in urban and sub-urban gardens. These offerings are a marked contrast to the occasional kitchen scraps that were placed on home-made bird feeding tables some 50 years ago. The question has recently been raised as to whether this is a good thing. In 2019, research by the British Trust for Ornithology indicated that this provision of food can affect bird communities in the United Kingdom. For example, species that rarely visited gardens in the past, have become common visitors. Now, researchers at Manchester Metropolitan University have suggested that these extensive offerings of food might be affecting the ecological balance between different species. Blue tits and great tits are regular feeders in gardens, and they appear to benefit from this provision. Blue tits tend to be be quite dominant in terms of their interactions with other birds - whether quarrelling over food or nest sites. Consequently, species like willow tits and marsh tits tend to ‘lose out’ in such altercations. Certainly, willow tits miss out to blue tits in the competition for nesting sites. Another species affected is the pied flycatcher. This is a summer visitor, spending the winter in West Africa. It, too, is in competition with great tits for nesting sites. The provision of food for resident bird populations may tip the balance against summer migrants, like the flycatcher. The change in feeding patterns of some birds may of course be associated with the expansion of farming over the decades and the consequent loss of natural foods such as fruits, seeds, nuts and berries - from hedgerow flowers and shrubs. This may contribute to birds visiting gardens more often. It may be that our desire to help garden wildlife needs more thought as to the type of ‘help’ that is offered. This could involve allowing our roadside verges and gardens to be ‘wilder’, with less frequent moving of lawns / grassy areas, more ground cover, planting native trees (like crab apples, hawthorn), less weeding, allowing seeds and fruits (eg. rose hips) to form, which would encourage insects / spiders Consequently more natural resources would be available to birds and only in harsh times would supplementary materials be needed. NB : it is essential that feeders are regularly cleaned so that disease is kept to a minimum [e.g. Trichomonosis caused by the protozoan parasite Trichomonas gallinae] . Remember later this month (28 - 30th January), there is the Big Garden Birdwatch, organised by the RSPB. For further information, click on the image below:- A footnote : As a species, we have not always been kind to birds. A recent paper from Tel Aviv University details how humans have been responsible for the extinction of hundreds of birds species (over the last 50,000 years). They have listed some 469 species of birds that have been lost, though the true number is probably considerably higher. Many of these extinctions occurred in a short time frame and were due to either : The hunting of birds (and their eggs) for food or The killing of birds by animals (rats etc) that human expansion brought to islands / countries. Many of the extinct species shared a number of features : Most lived on islands Many were large or very large birds (e.g. the dodo on Mauritius - that provided humans with significant quantise of high quality protein. (A similar fate befell certain large lizards and turtles). Many of the birds were flightless and could not escape their hunters.
Viruses, Varroa and honey bees.
Honey bees are often infected by the mite - Varroa. Mites are small arachnids. The varroa mite is an external parasite, attaching to the body of the bee and feeding from it. It also infects honey bees with various viruses, which further harm the bees. One such virus is the deformed wing virus. Bees that are severely infected with this virus die within days, some have such poorly developed wings that they cannot properly forage for nectar and pollen. The virus also affects their ability to learn, so that if they forage they may not be able to find their way ‘home’. Lost bees die, the colony is deprived of food collected by such bees and the colony may collapse. Eliminating the mite is difficult and the use of chemicals risks contaminating any honey collected from treated colonies / hives. However, researchers at the National Taiwan University have found a naturally occurring compound that may help alleviate the effects of the virus. The compound in question is sodium butyrate Na(C3H7COO). In a series of experiments, the research team found that bees that were fed sugar-water laced with butyrate were better able to resist the effects of subsequent viral infection. Compared to a control group that did not have butyrate, some 90% were still alive five days after infection whereas 90% of the control group died. The butyrate treatment also improved the bees’ ability to forage and return to the hive. Further details of this work here. Sodium butyrate is an inexpensive chemical, and if its benefits are substantiated then it could provide an affordable solution to the mite and virus problem that honey bees face.
Protecting woodlands from pests and pathogens.
The fact that UK is an island has kept many potential pathogens and pests ‘at bay’. However, in recent times the growth volume of international trade has become a cause for concern. Pests and pathogens can ‘hide’ in important plants and plant products (for example, timber that has not been debarked or suitably treated). The Great Spruce Bark Beetle is likely to have arrived here in wood that had not had its bark fully removed. The beetle breeds under the bark of trees, creating tunnels resulting in the destruction of the cambium. The cambium is a highly active tissue, producing new cells that will go on to form xylem and phloem tissue. These tissues distribute nutrients and water around the tree. With a damaged cambium, a tree is weakened and more susceptible to other pests or pathogens. In the case of the Great Spruce Bark Beetle, a bio-control measure was allowed; a natural predator of the bark beetle has been introduced (Rhizophagus grandis). Consequently, the numbers of bark beetles have fallen. Wherever the bark beetle goes, its predator sooner or later follows. It is thought that its predator ‘finds’ the bark beetles due to the volatile chemicals released from the bark as a result of the beetles' burrowing activities. The U.K.’s control measures generally proceed by four steps : Try to prevents pests and pathogens arriving in the country eg. Inspection of plants etc at ports of entry If a foreign organism arrives then the authorities try to eradicate the pest / infected plants / trees, hopefully the organism does not become established If a pest or pathogen has become established then a containment policy is put in place If all of the above fail then the Forestry Commission and other bodies operate in a way that mitigates the effects of the pest or pathogen. Phytophora ramorum is a disease of many plants that probably arrived here through the plant import trade. It has persisted at a relatively low level for many years but from 2009 onwards it affected commercial stands of larch in South West England. Felling of infected trees helps restrict the spread of this fungus-like pathogen; and a map is available to show where outbreaks of this disease have occurred. Clearly, these introduced species of pest / pathogen could significantly affect the make-up of our woodlands over the coming years, if diseases like acute oak decline / ash dieback are not controlled or contained. Fortunately, the spread of disease-causing organisms and pests is monitored by both national and international organisations such as these : EU Plant Health Directive this requires nations to report new outbreaks or new pathogens, t the European Mediterranean Plant Protection Organisation is an intergovernmental organization responsible for cooperation in plant health within the Euro-Mediterranean region and the International Plant Protection Convention, a plant health treaty signed by over 180 countries.
June’s Fungi Focus: Pocket Plum (Taphrina pruni)
In a month characterised by fruits and flowers, we turn our focus to a fairly commonplace fungi whose own fruitbodies are invisible throughout its life cycle. In fact, you never truly see the fungi itself, just the dramatic effect is has on the fruits of its host. Taphrina pruni is more commonly known as the Pocket Plum, or rather, the symptoms of this fungi are called the Pocket Plum. It is a biotrophic fungi, like the rusts mentioned last month, meaning it uses living plants as a source of nutrients, and while it won’t kill its host, its effects are hardly benevolent. Read more...
The woodlands blog has reported on the pathogen that causes ash dieback. Jasper has described the nature of the fungus, and Richard has commented on how the problem has developed. The disease has been variously referred to as chalara, ash dieback, and chalara dieback of ash. The fungus has an asexual phase, which was formerly known as Chalara fraxinea, hence the name of the disease; the sexual phase of the fungus was then associated with the asexual Chalara - this was called Hymenoscyphus pseudoalbidus. Putting the two together, the fungus was named Hymenoscyphus fraxineus (H.fraxineus). The fungus Hymenoscyphus fraxineus is of Asian origin. Read more...
The Giant Hogweed – a losing battle?
It seems that the UK is losing the battle to eradicate the giant hogweed. It is an invasive species which has been described as the country’s most dangerous plant. Many efforts have been made to eradicate this plant. Local authorities can make use the Wildlife and Countryside Act 1981 and The Anti-social Behaviour, Crime and Policing Act 2014 to enforce control of the weed. Sadly though Plant Tracker has recorded hundreds of sightings across the four nations of the U.K. Its scientific name is Heracleum mantegazzianum and it belongs to the same family as the wild parsnip, the Apiaceae. It is sometimes referred to as the giant cow parsnip, the giant cow parsley or the cartwheel flower. Read more...
Spittlebug Survey 2020
Last year, the blog reported on the disease that has been destroying the olive groves of Italy, and that is spreading in Europe. The research group (BRIGIT) centred at the John Innes Centre is appealing for help again this year to determine the distribution of froghoppers that could spread this disease IF it arrives in the UK. Spittlebug Survey 2020 Did you know that the ‘cuckoo-spit’ that you see in spring is produced by the immature stage (nymph) of a spittlebug or froghopper? It is thought that the spittle is produced to protect the nymphs from drying out and from their predators. Read more...
The lasting effect of Rhododendron ponticum in woodlands.
Atlantic oak woodland is often referred to as the Celtic Rainforest. It is characterised by lichen covered trees, together with a rich moss and liverwort flora. The environment is damp and humid, with streams and waterfalls contributing to this. These woodlands have evolved under the influence of the Gulf Stream, which helps keeps the area warm (and wet). The difficult access and rugged terrain (in some areas) has helped to preserve these woodlands, plus they have not proved suitable for agriculture or ‘industrial forestry’. Consequently, in many areas, they have remained in their 'ancient state', going back to the last ice age. Their sessile oaks are very important for wildlife but as they are not always productive of good timber, they have often been left to grow to maturity. By the same token, Birch trees have relatively low timber value - which has been their salvation. Woodlands like this were more extensive in the past covering the Atlantic fringe of Western Europe from North West Scotland down to the South of Portugal. This type of woodland is rich in terms of biodiversity (primroses, violets, wild garlic, ferns and grasses) and some species are only to be found here and nowhere else in the world. Read more...