26.1.12

Blight, Plague, Disaster, and other Maladies of Monoculture


Panama Disease
on Bananas


Some months ago I saw an interesting public-television program called "'The Botany of Desire", which was less salacious than the name suggested. It was based on a very popular book of why we have had affinities for some notable plants such as Tulips and potatoes. What caught my attention was the amount of detail given to the visually unremarkable modern potato, the vast majority of which is grown for the fast food market, primarily McDonalds' restaurant outlets. The problem is that just 1 variety is grown, the Burbank Russet variety, to the exclusion of virtually any other variety, since its long shape is perfect for making french fries that are long enough to stick up out of the serving container. Why would well-trained potato agronomists plant all of their farms with just one variety of a plant ? The answer is "money", since that plant type is what will sell or what is demanded. Why would such an agricultural method be noteworthy for a television program? The answer is "monoculture".



Potato Blight
the same disease that caused
Ireland's potato crop to fail



Growing vast acreage or countless thousands of a single variety of anything is a prescription for trouble. Many growers and cities and landscapers use large quantities of the same plant, whether it is  a coconut palm, Oak Tree, Elm, Ficus or Ash. If an insect or pathogen is introduced into that monoculture, the invader can undergo an unrestricted population explosion. Many areas of the world have seen whole provinces wiped out due to a disease. There are numerous examples, but some of the historically larger ones have been Panama Disease in Central America; Lethal Yellowing in palms in the New World, especially Florida; Potato Blight in the UK; Dutch Elm Disease in the eastern USA; Emerald Ash Borer in the eastern and northern USA; Hypoxylon Canker throughout the USA, and the list goes on and on. In Florida, we are at the forefront of introductions of new pests, and the range is broad, including fungi, bacteria,insects, reptiles, and of course, weed plants.



Dead Coconut palms in Jamaica,
due to Lethal yellowing
Sometimes the pests are part of a suite of problems, where a weed is introduced along with a pest, or an animal + pathogen combination is introduced, such as African Giant Land Snail containing the the parasite which induces human meningitis. Left unchecked in a monoculture, any pest or pathogen can wreak havoc and in some cases, throw a country into chaos, as in the Great Famine in Ireland in the late 1800s and early 1900s. Guatemala suffered terribly as its stalwart banana crop died in the early 20th century due to a highly contagious fungus ripping through massive plantations of the same kind of plant. Jamaica has seen its coconut plantations decimated by Lethal Yellowing. There have been grain and fruit crop failures which nearly bankrupted Asian countries. The numbers of dead plants and the amount of damage from introduced pests and diseases is hard to comprehend, certainly and provably in the billions of dollars. 





Dead Dutch Elms,
killed by Dutch Elm  Disease
The evidence is clear that over-planting a single variety of plant is just waiting for a problem to occur that will wipe out that crop . Yet in so many cases, municipalities and agriculture and homeowners repeat the problem. There needs to be much greater education at levels that diversity is the key to preventing such outbreaks, along with better landscape management practices. There are far better choices available to us now for disease-resistant plants than were available 30 or 40 years ago. We have a much better understanding in the landscape trade of the importance of looking into a plant's history to see if there are disease problems, but there are still too many instances of planting susceptible plants, and planting too many of them. 

The solution to monoculture is to plant a greater diversity of disease-resistant plants. An integrated solution calls for better education of nurserymen, landscape designers, and homeowners. The University Extension services of the US perform this function, but too few people pay attention to their please for education. These Extension Services are perennially on the budget chopping block . It is these researchers and information agents who can solve these problems for us at no charge to the residents, but they are underused and underpublished. As always, I make the plea to use information resources effectively to become educated. 


Craig Morell
Pinecrest Gardens                         

   

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