Scab-Resistant Potato Varieties
As an organic farmer, our arsenal against pests and diseases is limited. We choose not to use chemically synthesized pesticides to defend our crops against the pests and diseases which would damage or destroy our crops. Instead, we have to work with natural solutions to raise healthy and marketable produce. For us, this involves a combination of encouraging natural predators of pest insects, using pest exclusion techniques like row cover, and using naturally resistant crop varieties.
The use of naturally resistant crop varieties saves us a lot of work and planning, and is one of the most elegant solutions to the problems posed by pests. Naturally resistant crop varieties are those varieties which have adapted through evolution or traditional plant breeding to resist specific pests. This could be through physical alteration of the plant’s exterior, or subtle changes in the plant’s chemistry. Of course it is important to point out here that these changes achieved by traditional plant breeding are distinct from those of genetic modification. Traditional plant breeding takes generations of plants, genetic modification is done instantaneously and involves the genes of an unrelated species.
We use scab-resistant potato varieties in our field. Potato scab is caused by a bacterium-like organism, Streptomyces scabies, that overwinters in soil and fallen leaves. The organism can survive indefinitely in alkaline soils, so its definitely an issue for us. Here in the arid Intermountain west, soils are alkaline, which means they have a pH over 7. That’s not a bad thing in and of itself, some pests thrive in acidic soils, some in alkaline. Crop rotation and cleaning out old vines and tubers can help, but even in fields that have never grown potatoes, potato scab can still be a common problem. That’s why we use resistant varieties.
Below is a list of all the resistant varieties we have found to be truly resistant for us. Varieties range on a scale from somewhat resistant to completely, and these are those resistant enough for us to not spray and come out with blemish free potatoes: