Sunday, 12 January 2014

Where is horticulture going today? PART 2 - Chemicals

We are now in a spell of wet weather again although temperatures are still quite high for the time of year and many herbaceous plants are still partly in leaf or actually regenerating from the base along with a few flowers still to be seen on the basket fuchsias and the odd perennial such as phlox. Where I am in North West England we have so far escaped the severe weather which has dominated the last month and, although the garden is waterlogged in parts, it is generally not in too bad a condition. The small birds have not been on the feeders as much this winter probably due to the mild weather but, as I always leave the fallen leaves on the borders, I have been able to enjoy watching the blackbirds, thrushes and redwings flipping them over looking for the food underneath.



Schizostylis coccinea var. pictured in November but still going strong.

I have rather underhandedly changed part of the title of this series of posts from "domestic gardening" to "horticulture" because I realised that I would be using more references from commercial horticulture and as both amateur and commercial fields impact on one another it would give me more scope.

When I arrived at college in the mid nineteen sixties many things rather overawed me, but one thing that didn't was the use of chemicals for the control of pests and diseases as many of them were also available to the amateur gardener, and I was already quite used to selling products such as Lindane (gamma-BHC), DDT, Malathion and compounds containing nicotine and arsenic over the counter, so it is surprising really that this is the area of horticulture which, to my mind, has changed greater than any other in the last fifty years, and not always for the better.

If we concentrate on pesticides and particularly insecticides and fungicides the original remedies sounded like something out of a poisons cabinet with substances including arsenic, mercury, lead, copper, sulphur and nicotine being used liberally on the basis that if it killed you it must be bad for the insects and fungus. One dual purpose cocktail still available in the sixties was Lead Arsenate with Organo-Mercury used as a fruit tree spray!   

The two main groups of insecticide were chlorinated hydrocarbons such as DDT and Aldrin and  the organo-phosphorus compounds, now often known as organophosphates, such as Malathion, Parathion and Diazinon. The former have the disadvantage of being persistent, the latter, although dispersible, are extremely toxic to all forms of life including man, as they were developed from some of the most toxic substances ever produced which were to be used as nerve agents in warfare.

At this time I spent many hours spraying from a cabless tractor or by lance on foot without any form of protection whatsoever, whilst DDT was used in vast quantities as a domestic fly spray as we remained unaware of the potential dangers.
 
 
 In 1962 what was to become one of the most influential books of the 20th Century was published in America, Rachel Carson's "Silent Spring". The last time I read this book was in the nineteen seventies but, if my memory serves me right, I still remember some examples such as the case of carrot pickers being poisoned by Aldrin which had oxidised in the soil to produce a toxic level of Dieldrin. This book is often credited with initiating the changes which led to DDT being banned in the USA in the early seventies following which a worldwide ban was introduced (although not always adhered to) and subsequently most of the other more toxic "badies" have either been banned or had their use severely restricted throughout the world, particularly to the amateur gardener. Fungicides have been moderated, some of the basic ingredients remain the same and the changes have not been as drastic.

If we ignore the options available for commercial use, after having the potential fire power of a battleship in the war against pests, the amateur gardener has by comparison a pedalo-mounted peashooter consisting of the pyrethrins, some of their artificial equivalents and fatty-acids or soap. Although the synthetic pyrethroids such as Deltamethrin are effective enough to be used commercially the resources available somehow feel limited. Please don't get me started on "companion planting" and biological controls!

The demise of the "big hitters" was inevitable and lets face it when you are randomly spraying some of the most toxic substances know to man there are bound to be severe consequences. There is only one thing that I still find difficult to justify in my own mind; if we had carried on using DDT against the mosquito, would the long term effects on the human population have been as catastrophic as those of the disease?        
 

   


12 comments:

  1. Hi Rick
    Talking of DDT took me back to the mid 50s when my older brother and myself would go to the pictures (local fleapit) On occasions, the cinema usher would walk up and down the isles spraying DDT. My brother who suffered from bronchitis would go mental and just about come to blows with the guy. It certainly has been a mild Winter so far, just spotted blue flowers of Vinca had opened yesterday, pity its a plant I cant stand and will be getting the heave.

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    1. I remember happy days at the local fleapit also Alistair, two films a week then. Shame about the Vinca, cannot say I am a great fan but I find it handy for under shrubs where little else will grow.

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  2. thanks for interesting thought provoking post, Rick. How things have changed and people's consciousness raised about such things. But still there's too much poison used. And Carson's book didn't save the Vietnamese and the soldiers fighting in the war there, from Agent Orange. Alastair's post is hair raising.

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    1. Thanks for your comment, the problem with Agent Orange was that some of it was contaminated with a dioxin which is another substance which is residual, dioxins weren't banned until the early 2000's. Interestingly one of the producers of Agent Orange was Monsanto now leaders in genetically engineered crops which also generates much controversy.

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  3. A few years ago we suffered the consequences of an agricultural herbicide that contained aminopyralid. IT had been used to spray grazing land and had consequently transferred to the manure used on our site. Some people were still suffering contamination several years later due to the persistence of the chemical.

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    1. Thank you very much for your comment Sue and welcome to my blog. I have researched aminopyralid and I am surprised that it has been allowed to return after being banned, I can appreciate as allotment holders the misuse of herbicides is of particular importance to you. I noticed in the press that DDT has now been linked to Alzheimer's although the research is not extensive enough to be absolutely positive.

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    2. We were one of the first sites to link the problem to manure Rick and I joined forces with the RHS on the subject. In fact Gardeners World came and did a piece from out site and local radio and TV too. I gathered together all the information I could on my website here I'm still hearing of people suffering the effects to date. Then on the other hand there are few products available for the amateur gardener. We used to be able to buy a dip to counteract brassica club root but it's no longer available.

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    3. Thanks for the information Sue, it makes very interesting reading although to be honest I haven't quite got through it yet. I no longer have an allotment but was involved with a local group until recently so I was aware of the problem with manure.

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  4. Hi Rick, interesting piece from you again - and interesting question you raise at the end of your post. I certainly can’t answer it for you, but I suppose today it would be possible to simulate the effect and damage of use of DDT in a data program. Presumably that’s already been done and found too risky? I don’t know, but DDT has certainly got a stigma attached, even after all these years!

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    1. Thanks Helene, the results of a data programme may not be too convenient depending on which side of the fence you are on as we are talking big numbers here. DDT is still used for vector control and also in agriculture in a few countries through the world so production has not been altogether ceased.

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  5. Interesting point about how DDT saved millions of lives in controlling mosquitoes and malaria and in the control of locusts (Ok You did not mention the locusts!) A chemical that has had its day though and even if used now would be little good as many pests developed resistance all those years ago and it would soon return if, heaven forbid, it was used again. It was also a blunderbuss in that it killed the beneficial predators and parasites of garden pests. I would venture that the parathion you used was actually the worst chemical you used as to toxicity

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    1. Although it is still used today you are quite correct Roger, pest resistance would have probably meant that it would have become ineffective and consequently obsolete. Either way we went from the frying pan into the fire.

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