Rhododendrons and poisonous Honey?

A Bee feeding on a rhododendron bloom @ Steve Slater
A Bee feeding on a rhododendron bloom @ Steve Slater

An odd little piece of information came up the other day which happens to coincide with a few of the things we’re currently dealing with in the office.  Rhododendron Ponticum contains poisons which discourage grazing animals from feeding on them, this is fairly widely known and just another reason why Rhododendrons have to be controlled and another thing which makes the plant difficult to control.

This doesn’t usually affect humans because humans would never try to eat Rhododendrons but humans do eat honey.  The toxins are present in the nectar of the plant and Bees which draw a significant proportion of the nectar they collect from Rhododendrons can manage to produce poisonous honey.

The toxins in question are called Grayanotoxins and consumption of sufficient quantities can result in cardiac problems and even death while lower doses will result in excessive salivation, perspiration, vomiting, dizziness, weakness and paresthesia (pins and needles) in the extremities and around the mouth, low blood pressure and sinus bradycardia (reduced heart rate).  Looking on the bright side the condition is rarely fatal and generally abates within a day without medical intervention, but it’s still not going to be a fun experience.

It is very rare for toxic levels to make it into honey particularly in commercially produced honey however there are historical records of it being deliberately produced in Turkey going back to 400 BC when hives or sections of comb (depending on which version you believe) loaded with toxic honey were left in convenient locations to be discovered by hungry soldiers and poison invading armies.  Latterly in the 1700s this Mad Honey was sold into Europe where it was added to alcoholic drinks to give them some added kick.

John has been learning about bee keeping recently for an upcoming project and we’ve been removing a lot of rhododendrons which is how we stumbled onto this fact.  So now we, and you, know not to site bee hives in the middle of large areas of Rhododendron Ponticum.  Okay so this is probably not the most readily applicable advice for everyday life but interesting nonetheless.

TBT pollution from anti-fouling

This is what grows below the waterline on untreated ships @ Beth Oliver
This is what grows below the waterline on untreated ships @ Beth Oliver

We’ve recently been looking at ways to deal with TBT pollution and although it used to be a big environmental concern it’s an issue which doesn’t seem to be getting much coverage these days.  Tributyltin (TBT) is the active ingredient in a wide range of fungicides in preservatives for wood, textiles, paper, leather, plastics and packaging it is also used as a highly effective bio-cide in anti-fouling coatings for the hulls of ships and other marine infrastructure such as buoys.  Fouling is the term for unwanted plants or animals which grow on the hulls of boats.  TBT is highly toxic to a great deal of marine life including microalgae, molluscs and crustaceans, fish and some invertebrates.  It is encountered in higher concentrations in marine sediments in areas with lots of boats such as marinas and harbours and tends to affect bottom dwelling and filter feeding creatures but has been shown to bio-accumulate in other fish and even mammals.

In terms of environmental impact, TBT from anti-fouling coatings has been linked to high mortality of oyster larvae and abnormalities off the west coast of France in the 1970’s and the decline of the Dog Whelk in south west England in the 1980’s.  Malformations have been reported in a number of other species and immunological impacts have been noted in some fish.

The exact mode of action of the coatings varies a wee bit depending upon the product used but essentially there needs to be some degree of leaching of the bio-cide from the paint into the surrounding water to make it available to the life forms which would otherwise adhere to and grow on the hull of the boat. This means that TBT is released into the environment and, although initially expected not to be, it’s very persistent in the environment.  TBT and associated compounds will be broken down by exposure to light and oxygen but tend to adhere to particles in the water column and then accumulate in silt deposits where there is little light and not much oxygen.

So why use them?  Well, TBT containing coatings are by far the most effective anti-fouling chemicals ever developed and unprotected vessels may gather up to 150kg of fouling per m2 in 6 months.  To put this into context a Very Large Crude Carrier could have 40,000m2 underwater surface which translates to 6,000 tonnes of unwanted mass.  This massively increases drag and can increase the fuel consumption by 40-50%.  When scaled up to account for shipping world wide this becomes a significant amount of money and an environmentally significant volume of fuel.  Not to mention the potential environmental impacts of invasive species hitching a ride around the world on ship hulls.  Anti-fouling is simply necessary if we’re to have a global shipping industry.

As a result of the environmental concerns about TBT compounds their use was banned in anti-fouling coatings in an International Maritime Organisation (IMO) convention of 2001 which came into force in 2008.  This was the culmination of restrictions which began in the 1980’s.  It is estimated that 83% of the worlds merchant fleets (measured in tonnage) are registered to nations which have ratified this convention.  Alternative coatings are now widely available, usually based on other metal compounds.  However in nations with poor regulation the use of TBT continues and due to it’s persistence in the environment TBT contamination will remain a concern for the foreseeable future.

We’re currently developing techniques to remove TBTs from contaminated water which could greatly reduce disposal costs from their current high levels.  If you’d like to learn more about this please call us on 0131 538 8456.

Treatment window for Giant Hogweed?

Giant Hogweed before its giant
Giant Hogweed before its giant

It’s that time of year again, Spring has sprung, the grass is growing, the birds are singing in the trees and all of the invasive plants are also rearing their ugly little heads.  Giant Hogweed is a particularly unpleasant one because as you can see in more detail here the sap can cause really very nasty injuries if it contacts your bare skin.  At this time of year the plants are small and to the untrained eye they are much more difficult to tell apart from the less harmful native Common Hogweed plants.

This is also the easiest time of year to do something about Giant Hogweed, the ideal treatment window varies for different invasive plant species and this is the time to think about Hogweed.  No matter which method you intend to use to manage your Giant Hogweed the health and safety implications of working around a plant with sap which can burn your skin and can go on to develop a roseatte of leaves each over 1m in width and a stem which can grow up to 5m in height are considerable.  As someone who’s carried out both physical and herbicide control operations on stands of mature Giant Hogweed I will personally testify that it’s much easier in every aspect of the treatment if you’re not wading through chest high leaves swathed in protective clothing.  Those were exceptional circumstances and by careful planning and attention to detail we were able to perform this work safely and successfully but if we’d been contacted at the start of the season it would have been much quicker and simpler.

Right now the plants are small and you can move around them without having to make physical contact with them (unless you’re physically destroying them).  The treatment window for treating Giant Hogweed is now wide open but it won’t stay that way indefinately.  If you’ve got something that looks like the plant in the picture above sprouting in your garden or on your development site then don’t hesitate to get in touch and we can definitively identify it and deal with it for you, if needed.