damp weather encourages the fungus. This may have been a contributing factor but it's not the cause. What I know about the potato came from the book Propitious Esculent, The Potato in World History by John Reader. He said the potato late blight came out of a valley somewhere in Mexico, wiped out the potato crop in New England and was carried across to Belgium in a shipment of seed potatoes. It then proceeded to wipe out the entire potato crop in 2 million km2 of Europe in FOUR MONTHS.

You can't blame Irish land degradation for this - the crop failure happened everywhere. It was an opportunistic emerging disease. The death toll wasn't limited to Ireland because the potato was the food of the poor in a number of countries. But ultimately what killed people wasn't the lack of food but the lack of money to buy food, just as it is today.

The shortage of food triggered hording and profiteering which drove up the price of all foods, especially grain. The same thing happened last year with the rice 'shortages' and we'll see the same thing happening when peak oil sets in.

The English government's response was to order grain from the US in secret (to prevent profiteering), scrap the protectionist corn laws which cost the prime minister Robert Peel his job (the farm lobby weren't happy), and set up food relief.

You can blame nasty people for being nasty but humans have a tendency to blame everything on someone else. The bottom line was - no blight, no famine.

It is worth commenting on the status of potato blight. The organism (Phytophthora infestans) causing blight is always present to some extent in potato growing areas. To take hold on the potato vine the spores need continuously wet foliage for 48 hours. This can be caused by dew, pissy rain, fog and/or imprudent watering (irrigation).

Many areas are capable of experiencing these wet conditions. In large potato growing areas such as Idaho, it is often necessary to spray with fungicides weekly during adverse conditions. This bodes badly for people who have to consume, unknowingly potatoes from treated fields. The first signs of infection are usually mottled black spots on the leaves of the plant. Once established, the disease rapidly goes systemic and black spots appear on the stems too. There is no saving the plant once this happens. In addition, if the crop has developed tubers, the disease enters the tubers too making them unsuitable for eating or storage.

The disease spreads with amazing speed often infecting areas 200 km down wind in one day. Spoors have been detected 200 km at sea off of blighted areas. This disease also infects tomato plants with similar devastating results. The progress of the disease on tomatoes is nearly identical to that observed for potatoes. Often the disease appears just when plants are at peak growth and just developing fruit or tubers in the case of the potato. It may be that the stress of putting on fruit (or tubers) makes the plant more susceptible. A day or two before visible spotting appears, the plants often look the greenest and most lush of the growing season. Then just when you are congratulating yourself on your lovely crop the spots hit.

My experience is that once the disease has hit tomatoes in your area, it is nearly impossible to grow tomatoes on open ground for years afterward. For an organic producer like myself this means it is necessary to treat the plants constantly with Bordeaux mixture which is an inorganic copper spray. In spite of these treatments, damage can appear. Since I do not want me or my customers to eat tomatoes treated with this spray, I only grow tomatoes in greenhouses using reusable plastic on the ground and drip irrigation underneath the plastic sheets. The foliage never stays wet under these conditions and in our hands have never been affected by the disease even though we do not treat the plants with fungicide. Such a solution is a lot of work for the grower but the results are well worth it.

We reluctantly use Bordeaux spray on our potatoes but one must use it as a preventive treatment especially late in the growing season. At least the spray does not get on the tubers.

Relating to Ugo's article, is the fact that this viscous disease is always waiting to raise its ugly head and wipe out crops world wide. Should fungicides be difficult to obtain because of economic-peak oil reasons the world will be in deep doo doo.

Many other important crops have similar problems with disease including the important banana. Bananas are threatened with the fungus Black Sigatoka which has now spread over much of the tropical world. This nasty disease is threatening the very existence of millions, perhaps billions, of people who depend on it for food. Large banana producers treat their crop every time a new crown of leaves appear. Thus, the fruit is exposed to incredible amounts of organic pesticide and so are the consumers. Worse yet, one major cultivar, Cavendish, is grown in industrial banana production. This strain is highly susceptible to the disease and at present there has been no replacement found for the Cavendish that resists the disease.

Thus, survivalist-mentality people must be aware that dependence on common food crops such as the potato can be very risky. Diversity in food production is the best bet.