|
 |
 |
 |
 |
 |
Growing Potatoes: Late Blight
Phytophthora infestans is a water mould, that causes the serious disease of the potato, late blight or potato blight. The early stages of blight are easily missed, and not all plants are affected at once. Symptoms include the appearance of dark blotches on leaf tips and plant stems. White mould will appear under the leaves in humid conditions and the whole plant may quickly collapse. Infected tubers develop grey or dark patches that are reddish brown beneath the skin, and quickly decay to a foul-smelling mush caused by the infestation of secondary soft bacterial rots. Seemingly healthy tubers may rot later when in store.
The potato blight caused the Irish Potato Famine in 1845-49 which, it is estimated, caused over 1,000,000 to starve death and forced a further 2,000,000 to emigrate.
The spores of this water mould overwinter on infected tubers, particularly those that are left in the ground after the previous year's harvest, and are spread rapidly in warm wet conditions when blight can have devastating effects, destroying entire crops. Spores develop on the leaves, spreading through the
crop when temperatures are above 10°C and humidity is over 75% for
2 days or more. Rain can wash spores into the soil where they infect
young tubers, or else spores can be blown in from distances of up to
miles by the wind.
Bordeaux mixture is a combination of copper sulphate
and hydrated lime, invented in the vineyards of the Bordeaux region
of France, and used mainly to control garden, vineyard, nursery and
farm infestations of fungus. This fungicide has a history of over a
century, and is still used, although the copper can leach out and pollute
streams.
This flaming process uses our patented liquid spray torches which are specially designed to spray liquid propane into the vines where combustion takes place. The canopy of vines and foliage help hold the heat helping to make more efficient use of the fuel. The intense heat thermally shocks the green vines and destroys cell tissues in the leaves, destroying the plant’s ability to conduct photosynthesis. Flaming is also a very effective weapon for blight control. Chemical treatments are expensive, and not an option for organic growers. Flaming to desiccate or scorching the ground right before harvest will help control blight spores.
Up until the 1970s, there was only one type of blight (A1) in the UK, and this was unable to produce resistant spores that could survive the winter. There are now two types (A1 and A2) which can mate and after that produce resistant spores, although the indications so far are that this rarely, if ever, happens in the UK. Mating can occur only between moulds of different mating-types and is required for the production of resistant spores. Prevention and control of potato blight can be achieved by planting only good quality seeds obtained from certified suppliers. Do not save your own seed for replanting, and try to ensure that no ‘volunteer’ tubers are left in the soil after harvest. Potato varieties vary in their susceptibility to blight. Most early varieties are very prone; so that the crop matures before blight starts (usually in July) plant them early. Maincrop varieties which are very slow to develop blight include Cara, Stirling, Teena, Torridon, Remarka and Romano. Some so-called resistant varieties can resist some strains of the blight and not others, so their performance may vary depending on which are around.
Learn more here: Irish Potato Famine introduction U.S. Potatoes Could Get Disease Resistance from Their Mexican Cousins Red Dragon Agricultural Flamers Tubers naturally mature as the plant senesces. With the improved production methods, potato vines remain healthy and green longer into the season. It is argued that for proper tuber maturity at harvest, vine desiccation is necessary. Vine killing benefits tuber appearance, limits tuber size, improves tuber release from the vine at harvest, reduces tuber skinning and can lower crop susceptibility to shatter. Some additional benefits include harvest timing, tuber ripening, tuber size management, disease management, and improved storage life.
Spraying potatoes: health risk for potato farmers
These products are categorised by their toxicity. The most dangerous carry a red warning label. In this region of Ecuador, 90% of all the pesticides bought are red label products.
Many die The doctor at the local hospital says he sees the results of acute pesticide poisoning every day. People are admitted with stomach cramps, blinding headaches, serious skin diseases, and tunnel vision. The most serious cases have kidney failure, or have taken an overdose of pesticide. Many die. The statistics do not reveal the thousands of cases of dizziness, nausea or memory loss which are not referred for medical help - nor the cases of cancer, depression or fertility problems which have been linked to certain chemicals. Researchers in this area of Ecuador say farmers, their wives and children are all at risk, and six out of ten will have suffered nerve damage due to pesticide exposure.
Pesticide salesman When he is pressed to say why he does not sell less hazardous products, he explains it's all a matter of demand. Farmers want the strongest pesticides possible, and they do not buy the alternative products. Most farmers and pesticide suppliers will have had no formal training about these highly hazardous substances. Researchers and campaigners say the challenge is to get information down to the grassroots as quickly as possible.
|
|
| Copyright: The Potato
Museum 2005 About | Exhibits |Potato Blog |Links | Contact Us |Museum History | Educators | Home |
