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| Department of Agriculture and Aquaculture |
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To grow potatoes organically producers face all of the same pest, weed and disease challenges as other farmers, but must deal with them using a completely different array of solutions.
One disease in particular, late blight, can have a huge effect on potato yields and thus presents a major challenge to organic growers. Late blight destroys the foliage of the potato plant and can also affect the tuber. This disease over-winters on affected tubers and is remarkable in its ability to spread from the initial infection site and develop quickly. The most effective method of preventing damage in traditional production is to protect the plant by using preventive sprays of anti-fungal agents. Organic producers have relied primarily on two agents to provide them with a measure of protection. The first one, copper, is a chemical that has proven efficacy. Another method, compost tea, is used regularly by organic producers and is reported to have some efficacy. There are now brewing devices on the market that make it possible to obtain a reliable, effective and safe product.
Clean seed and the use of early maturing varieties that have been sprouted to advance maturity are both important to ensure a crop early in the season before late blight has had a chance to strike. Wider row spacings that improve air circulation will reduce the risk of infection. Large hills can also prevent late blight infection by making it more difficult for the spores to reach the tubers. And finally, allowing 3 weeks from topkill to harvest prevents the tubers from being infected from live spores.
Some commercial potato varieties are more resistant to late blight and can provide a measure of protection. There are now breeding programs all over the world trying to develop suitable late blight resistant varieties.
Weed control is also a major issue in the organic production of potatoes. Specialized machines such as the finger-weeder will control weeds effectively at an early stage of growth. A propane flamer can also be used at this stage. Hilling operations later on in the season will help keep weeds under control as well. However, most important measures to control weeds are the use of good crop rotation practices and ensuring that annual weeds never go to seed.
Top-killing, a practice required by both traditional and organic agriculture, is the deliberate destruction of the foliage of potato plants. It is necessary to schedule harvest operations, encourage skin set on the tubers, or to stop the spread of disease. In an organic system it can be done with a propane flamer but more than one pass is usually necessary. Vine-pullers are also an option in certain areas and roto-beating could be used alone or in conjunction with flaming.
One of the most critical areas of research for organic growers will be the continued development of varieties that are adapted to organic methods of production. Resistant varieties by themselves will not be a silver bullet. There will always be a need for more research on biological and mechanical methods of pest control. Growing potatoes organically will not prevent the development of resistance in weeds, insects and diseases. For example, weed control methods may select for weeds that germinate later and these later-germinating weeds may eventually become dominant in the field.
Although there are already numerous organic solutions to pest control problems, not all of them are both efficient and profitable on a commercial scale. The evolution of organic production methods will require a tremendous on-going research effort in all aspects of pest and weed control. Fortunately this research will benefit all of agriculture as methods of disease and pest control are developed that reduce or eliminate the need of chemicals. Already, regulatory policies make the registration of reduced-risk and biological pesticides easier, faster and less costly.
The magnitude of the growth in sales of organic produce makes organic production difficult to ignore. While organic production will not be for everyone, it is certain that in the future producers with the right set of skills and marketing plan will be successful in this new area of food production.