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?