[MUSIC PLAYING] SPEAKER 1: This is a production Cornell University.
SPEAKER 2: Welcome to the podcast of Mann Library's Chats in the Stacks Book Talk series. In today's, talk, originally presented at Mann on October 13, 2011, Walter De Jong of Cornell's Department of Plant Breeding and Genetics provides an overview of topics covered in his newest publication, The Complete Book of Potatoes. Beginning with the potato's importance to human civilization, Dr. De Jong's talk touches on this crop's versatility in food and nonfood uses, its disease-resistant varieties, conventional and organic production techniques, pest management, storage practices, and the sometimes surprising culinary qualities associated with different varieties.
WALTER DE JONG: Thanks very much. If you have questions in the middle of the talk too, that's perfectly fine. I have a PowerPoint talk. And I can-- my wife, at the back, cannot hear me.
I'll speak louder. So I've prepared a talk, in case no one asks questions. But I fully expect that some of you will want to interrupt. And wave your arm wildly or something, and hopefully I'll notice.
So today I'm talking about a book that I was part of writing along with my father and Joe Sieczka. There's a picture of us here in the next slide-- me on the right, my dad in the middle, and Joe Sieczka on the left. My father was a potato breeder with Agriculture Canada throughout his career.
Joe Sieczka is retired from Cornell. He worked most of his career on Long Island. Both of them spent their entire careers working with potatoes. Assuming I have a normal lifespan, I'm closer to the beginning than the end of my career in comparison.
So my two co-authors, in particular, provide an awful lot of practical experience in the book, much more so than I did. I guess that's enough said for that.
So the book covers a wide range of topics. Clearly, there's the subtitle, which I'll get back to in a minute, about what every gardener and grower needs to know in terms of growing potatoes. But it also covers a lot about the history of potato, where it was domesticated and how it moved around the world, common diseases of potato, and some other interesting tidbits. I'm just jumping around to various parts of the book today, not in any specific order. I'm trying to get the stuff that's relevant from the gardening standpoint out of the way earlier in case I run out of time.
So potatoes are currently the world's third most important food crop. But what's kind of amazing is that 500 years ago, they were only located in South America. And they weren't grown anywhere else. It wasn't until Europeans came to South America and brought them back to Europe, at which point they didn't do much for 200 years. But in the last 300 years or so, the spread of potatoes has been phenomenal, to the extent that they're now the third most important food crop in the world.
There are a variety of reasons why potatoes have become so popular. One is that they're nutritious, for example, having a lot of vitamin C. In the North American diet, with the per capita potato consumption, about a third of our recommended daily allowance of vitamin C comes from potatoes alone. A lot of potassium. And while not so much protein, the protein is actually a very high quality.
In addition to that, potatoes produce an awful lot of calories per unit of land. So especially if you're poor, and you have a limited amount of land, and you need to survive, potatoes are a really good choice of a crop to grow. And in addition, potatoes have an awful lot of genetic diversity, which allows breeders to adapt them to a wide range of environments. So it's that combination of things which has led potatoes to become so popular and widely grown throughout the world.
Potatoes were first domesticated, it's thought, about 8,000 years ago around Lake Titicaca, which is on the border between Bolivia and Peru. Lake Titicaca is the highest navigable lake in the world. And in order for potatoes to become domesticated and spread around the world, there were really two key things that had to happen. The first was that we had to find ways to deal with glycoalkaloids, which are bitter and toxic compounds that accumulate in wild potatoes. And the second, which I get to, is about becoming adapted to long days.
You probably have experienced what glycoalkaloids taste like when you've eaten the part of a potato that's green. The green is just chlorophyll. That's not a problem.
But when potatoes are exposed to light, they also produce these glycoalkaloids, which are bitter. And if you eat enough of them, you'll get quite ill. And if you eat too much, you'll die.
So there are different ways to cope with glycoalkaloids. In some parts of South America-- this is not widespread-- it turns out they've discovered, if you eat a particular kind of clay at the same time as you eat potatoes, you're good to go.
Another one is this ancient process of freeze-drying the potatoes that is still currently practiced in some parts of the Andes where the potatoes that have glycoalkaloids are left out to freeze at night, then are trampled to break them open and left in a stream for the glycoalkaloids to leech out. And the starch is left behind.
And the very lightweight product after you put them up, again, to dry is called [QUECHUA]. And you can store it for a year or more. So it gets around a problem that we have with potatoes for long-term storage. If you freeze-dry them, you can store them for a long time.
And the way, of course, that has really allowed potatoes to become widely adapted is for someone to have, early on, identified plants that were relatively low in glycoalkaloids and then selectively propagated those. And that, of course, is what we currently eat as potatoes are potatoes that are low in glycoalkaloids, because someone identified them-- those that had low levels-- and multiplied them.
Another big and important development for potatoes to spread around the world was for them to become adapted to long days. So wild potatoes normally will tuberize only when the days become relatively short. And so if you took a wild potato from the Andes and brought it here, you'd get no or very few potatoes. Most of the time, the potatoes would freeze before the days became short enough for them to produce enough of a crop.
So this is a process that took, conceivably, quite a long time. And it's something that breeders have been dealing with over the past few centuries as well-- adapting potatoes more and more to be adapted to long days. So the end result is that while potatoes started off in a little area in South America a few thousand years ago and spread a little bit within South America, today, if you look at where potatoes are produced, it's all over the globe.
And potato production has continued to change even over the past 20 years in particular, where now Southeast Asia produces a remarkably large number of potatoes China is now the world's number one producer of potatoes. And India comes in second. Together, those two countries produce a third of potatoes.
I'm guessing that most of you don't think of Chinese as potato eaters. I can't say that I did either. I was in China this past summer. And certainly, in northern China, finding potatoes isn't hard. They're just about everywhere.
This was the picture of a mountain I took. I called it Potato Mountain because that's all they had on the mountain-- potatoes as far as the eye could see. So again, just in a few hundred years, potatoes have spread phenomenally. I'm sure that when Columbus came to America and subsequent explorers, they were thinking about bringing riches back to Europe in the form of gold and silver. But with the aid of hindsight, really, the two big things that they brought back from the Americas were potatoes and corn, the number three and number four food crops around the world.
So the subtitle of the book-- what do you really need to know to grow your own potatoes? Having grown up in a Baptist church, I feel like I need to give a three-point sermon. And so these are my three points, just to get straight to the chase. And then I'll just meander.
So the first thing is that choosing the right variety makes a big, big difference in your success. And I'll elaborate on that. The second is that starting with certified disease-free seed also makes a really, really big difference in terms of your success.
And since I need a third point, adding some fertilizer and water helps too. I won't comment more on fertilizer and water, other than to say, if you want a specific recommendation, about 3 and 1/2 pounds of 10-10-10 fertilizer per 100 square feet. And keeping water-- keeping the soil moist but not drowning is good. Potatoes do need a lot of water. In Ithaca, in our well-drained soils that my breeding program operates in, we're aiming for least an inch of water a week.
OK, so potato varieties differ in an awful lot of characters. Any two potatoes in particular are far more different from each other than any two of us are different from each other. And of course, we all like to think we're very different from each other. Potatoes have more genetic variation than most crops.
And so if you take any two potato cultivars, you'll find that they differ in a large, large number of traits. You'd expect them to differ in disease resistance. You'd probably expect them to differ in yield.
Maybe you realize that they differ in cooking qualities and eating qualities. They also differ in length of the growing season and how well they store and an awful lot more. And so this sort of comes to the point of choosing a variety that has the attributes you want is kind of important if you want to be successful.
Currently, the most popular potato variety in North America is Russet Burbank. It was developed by Luther Burbank in the late 1800s. And it has high yield and excellent taste and stores really well.
So I guess the natural question is, well, what's not to like? And I pick on Russet Burbank because, to illustrate the point of why it's important to choose a right variety, if you grow a Russet Burbank in New York, almost all of your potatoes will look like this. The eyes have sprouted and formed tubers. And sometimes a little tuber that has the eyes on it then form additional tubers. And it just gets really, really hideous.
Russet Burbank is really, really hard to grow in New York. In order to grow it well, you have to manage water exceptionally carefully. It's hard enough to do out West. And it's really hard to do here too.
So this is the kind of thing that can happen if you don't choose your variety well, in addition to just having a really low yield. By the way, Russet Burbank was not actually the potato that Luther Burbank developed. He developed a potato that was just called Burbank's Seedling. And it wasn't russeted.
Russet Burbank is a mutant of the original Burbank. And it has russet skin, unlike the original Burbank. That's the only difference. It has russet skin.
This has actually caused a big problem for potato breeders in the century since because consumers have come to associate russet tuberous skin with high quality. Russet skin has nothing to do with quality, per se. But if that's what you expect to see in the supermarket and that's all you'll be willing to buy, breeders who develop potatoes, particularly in the West, are forced to develop potatoes with russet skin. And it's a hard trait to develop. I guess it's listed here that the Russet Burbank was found 20 or 30 years after Burbank was-- the seedling came about by a farmer in Colorado.
Luther Burbank wasn't actually impressed with Russet Burbank. He thought it wasn't a good thing. This is the picture of Luther Burbank. That's actually a postage stamp. As far as I know, he's the only plant breeder who ever made it onto a postage stamp, certainly the only potato scientist who made it on. I think all potato breeders aspire to getting their picture on a postage stamp.
So I suspect that many of you have never really considered that the starch content of potatoes has a profound impact on cooking and eating quality. So in particular, potatoes with high starch are very well suited for making French fries and potato chips, primarily because they absorb less oil. Water in the tuber gets replaced with oil when you fry it. And the more starch you have, the less water you have, so you don't take up so much. So French fry companies and potato chip companies like potatoes with high starch.
Potatoes with high starch tend to have a very mealy texture and are kind of somewhat dry when baked, but also disintegrate when boiled. So if you want to boil a potato, I don't recommend boiling high starch potatoes, unless you want them to disintegrate. As a rough rule of thumb-- it's not absolute-- most russet potatoes are high in starch.
On the other hand, low-starch potatoes generally hold together when boiled. And if you bake them, they're kind of moist. And these potatoes are more suitable for things like salads. And as a general rule of thumb, red-skinned potatoes are low in starch.
I never realized until I became a potato breeder why I liked red potatoes. It has nothing to do red, per se. It's that I personally prefer low-starch potatoes.
But I know many people have a preference for high-starch potatoes. My observation when we were running blind taste tests in my own breeding program was that the primary differentiator between people was whether they prefer high or low starch. And I think you'll each know who you are.
When it comes to round, white potatoes, they can be all over the map. Some are high. Some are low. It just depends.
So I've already illustrated why I think you probably don't want to grow Russet Burbank in your garden. So maybe it helps if I give you something that I would suggest you grow. The favorite potato of-- my favorite potato and that of all my staff-- and it wasn't because I dictated it to be the favorite potato. My staff actually convinced that it's a potato I should eat-- is Andover. And on the side wall over here are 10-pound bags of Andover that you're free to take with you and eat yourself. So you can see this.
It turns out Andover was developed by my predecessor, Bob Plaisted. And it was originally intended for making potato chips. In my first few years at Cornell, I didn't want to eat it. Like, why would I want to eat a potato for potato chips?
Until we began running these blind taste tests and it kept coming out on top. Eventually, the data persuaded me. And I've been eating Andover ever since.
I don't want to pretend that Andover is the easiest potato to grow. It isn't. The vines are kind of weak.
And if there's a drought, it doesn't hold up very well. But in terms of eating quality, it's really good. And anyway, you can see for yourself if you take a bag.
So additional attributes of Andover is that it matures early. I mentioned that potato varieties differ in their maturity and when you can dig them. Andover, oh, you can dig them as early as the end of July, middle of August. That's fine. The vines mature early.
It stores OK. And in terms of eating them at home, in general, as a breeder, I don't try to develop all-purpose potatoes, because the potato markets for French fries and chips and fresh are quite different. But I'd consider Andover about as all purpose as they come.
And so in our experimental plots, when we have an extra row on the outside of a plot, we plant to Andover. We harvest a lot of Andover. And it's what I and my crew eat. So if I had to make a single recommendation, it would be to grow that.
SPEAKER 3: [INAUDIBLE]
WALTER DE JONG: Sure.
SPEAKER 3: [INAUDIBLE]
WALTER DE JONG: Not very good.
SPEAKER 4: We didn't hear the question.
WALTER DE JONG: The question is, how resistant is Andover to late blight? And I guess maybe I should expand on that. Nothing has good blight resistance. Not, in general, very good.
Late maturing varieties tend to have better blight resistance than early maturing varieties. But, well, nothing is especially good. Nothing's completely immune.
In the book, we actually provide descriptions of about 55 potato varieties. The book is intended primarily for an audience all across North America. And we had to cover potato varieties grown everywhere.
What I'm doing in my next few slides is just picking on some varieties that I think, if you want to grow potatoes around here, are reasonable choices. Of course, you can grow more than I'm describing here. But from my experience in this area, these will do fine. And it's a bunch of different types that I'm suggesting.
If you'd like to grow a red, Chieftain is an old variety. It's been around for quite a long time. It has good eating quality, is widely adapted, meaning it will grow well just about anywhere. And in a practical terms, what that means in a given region is no matter how bad the growing season is, you'll still do OK. It's also resistant to common scab, a trait I'll get to in a minute.
If you like yellow-fleshed potatoes-- oh, there's a table in the middle of the room where there are few of the varieties that I'm talking about today. There's some Chieftain there. And there's also some Keuka Gold. Keuka Gold is the yellow-fleshed variety named after Keuka Lake, one of the Finger Lakes.
If you want to feel like a hero when you're a gardener, grow some Keuka Gold. And I say that because Keuka Gold is the highest yielding variety that was ever developed by Cornell. Again, released by my predecessor, not by me.
And it's really hard to go wrong with Keuka Gold. It'll certainly crush Yukon Gold in terms of yield. And the eating quality is also pretty good. And it's resistant to common scab, which is an attribute that I think many of you will find you wish you had resistance for when you grow potatoes.
And when we've run-- put potatoes into various organic trials, Keuka Gold has typically come out in the top yield in those trials as well. Not to say it's so resistant to everything. But it just yields so much that you still get a decent yield regardless.
So common scab. Common scab's a soil-borne organism. It's kind of ubiquitous. If you put not completely composted compost or manure in your garden to increase the organic matter, you're likely to have increased problems with this.
Nothing is completely resistant or immune to common scab. It's all relative. But, well, these are four different potato lines that were grown in the same field. And you can see what I mean by relative. Some of them held up pretty well, and some of them got hammered.
If you see deep pits like this in your potatoes, look to see what's resistant to common scab and plant that next year in your garden. I can guarantee some of you will experience this. Just pointing out that, in terms of an important attribute in varieties, if you have common scab is to look for something with resistance, like Chieftain and Keuka Gold.
Another fun potato to grow is Caribe. It's a purple-skinned potato with bright white flesh. It's also early maturing. Probably the most embarrassing moment in my entire life was when I once asked my dad, after I'd been here for a few years, if he knew anything about the variety Caribe. And he said, yes, I bred it.
There are certain things you can only walk into in when your father and you are in the same profession. So I suggest Caribe if you're interested in a purple-skinned potato.
Another potato that some of you have likely heard of was released during my time here. The breeding was largely done by Ken Paddock, a former employee in the potato program-- Adirondack Blue, which has completely purple flesh. All Blue, which might be a purple-flesh variety you know of, does not have completely purple flesh.
All Blue is not all blue. All Blue is blue and white. Adirondack Blue is all blue in terms of being completely purple.
If you cook Adirondack Blue, I'd suggest not boiling it, because the purple pigments are water soluble and will leech out. Bake it, or microwave it, or fry it, and you'll retain more of the purple color. We also have released a variety called Adirondack Red, which is red inside. I don't have a picture of that here.
For me, one of the more interesting potatoes I've seen in the past few years is Papa Cacho, a Chilean heirloom variety that was introduced into New York State by my colleague Keith Perry, who runs the New York State seed farms in the Department of Plant Pathology. Papa Cacho doesn't yield very high. But the tubers are really interesting.
There are a couple Papa Cacho tubers on the table and a potato from a cross with Papa Cacho. The tubers can be like 8 or 10 inches long. They're unlike anything you'll find in a supermarket here. So if you just want to have fun, Papa Cacho is fun.
And I think the last potato I'll mention that's described in the book is called Ozette. Ozette is different than most North American potatoes because it didn't take the usual trajectory of potatoes into North America, meaning from South America to Europe, and then spreading to North America. Ozette seems to have come to North America directly from Chile, brought up by Spanish explorers and brought to the Native Americans who lived on the West Coast at the time.
It was found a few years ago that the Makah Nation were growing Ozette, It's a really special potato to them. They are unwilling to sell it to anyone. But they are prepared to give it to you as a gift.
So they think that it's too important to sell. But it can be given as a gift. I hate to admit that you can actually buy this from at least one company on the internet. But Ozette has-- well, it's somewhat long, yellow flesh, with lots and lots of eyes, kind of a pine cone appearance. And it has a unique appearance, clearly.
So earlier I mentioned that there are three things you need to do to ensure your success. Choosing the right variety is important. And another really big one is starting with disease-free seed. So if you happen to repeatedly plant your potatoes year after year after year after year, you'll almost inevitably see that the yield will dramatically decline over time-- maybe just one season. And this happens because potatoes accumulate diseases, especially viruses.
Once a potato plant has a virus, all its daughter tubers will have a virus. And they'll act as the source of inoculum the next year. And yields will go down.
So the way to get around this is to, every year, start with what is called certified seed. It's certified to be free or at least very low in diseases, especially viruses. I actually don't know if you can still do it. I know when I last looked, you could buy certified seed of some varieties from Agway in Ithaca. You can also buy certified seed from lots of different companies through mail order or on the internet.
Supermarket potatoes are generally not a good source of seed, in part because they may harbor diseases that you don't know about. And sometimes because they're sprayed with sprout suppressant, and they just won't sprout. So that won't get you anywhere. So you should really start with disease-free seed.
In terms of what to do with seed-- yes.
SPEAKER 5: Sprout suppressant?
WALTER DE JONG: Yes.
SPEAKER 5: What is that? And what happens if we eat it?
WALTER DE JONG: So the levels and you would find, the FDA or whatever agency regulates this will have deemed are not dangerous for your health. But what they do is they stop the sprouts from growing.
SPEAKER 3: Is it a plant hormone?
WALTER DE JONG: Well, they can be plant hormones or various analogs.
SPEAKER 5: [INAUDIBLE]
WALTER DE JONG: Well, the industry is trying to move away from sprout suppressants and is looking for potatoes that have longer dormancy. But it can be an issue.
Yeah, so if you're going to plant potatoes, depending on what size of potatoes you get, you'll find you may have to cut them. Ideally, it's easiest if you get little potatoes that are about 2 ounces in size and you can plant the seed pieces whole. But if you get them larger, you have to cut them.
This is sort of a diagram-- it's from the book-- about how you can cut round seed pieces in order to ensure that each piece has at least one eye. And the final seed pieces are each about 1 and 1/2 to 2 ounces in size. If you're cutting seed from a long potato, well, you really only have one choice about what axis you'll cut them on. Just make sure you cut them so each piece has at least one eye.
A question I get asked a lot from potato novices is how deep to plant. And I guess the questions that follow after that is how far to plant them apart in a row. I'd say 9 inches or so is a good starting point for how far to plant them apart in a row. And how far should the rows be apart? About 3 feet.
In terms of how deep to plant-- well, I guess I'll answer the question first. About 3 to 4 inches is where you start. And it helps to consider how a potato plant grows to understand why we have to plant them at that depth and why we end up hilling the plants as the season goes on.
So initially, you plant the seed piece. It's sort of diagrammed as the mother tuber here. And the roots go down. And the shoots go up.
Potatoes are underground stems. And they form at the end of horizontal stems that we call stolons. All the stolons, of course, have to come off of the stem that has gone up. So they're all starting at a point that's higher than the mother seed piece. So daughter tubers form above where the seed piece was.
So you need to plant at some depth-- 3 to 4 inches, I guess is what we're recommending so that the tubers can form. There's still soil for them to form. But not too deep, because if you plant the potatoes too deep, it takes too long for the shoots to come up. And there are all sorts of soil-borne fungi that can attack them and kill them before they ever make it. So there's this balancing act in that regard.
Of course, when you're growing potatoes during the year, you normally pile some soil up on the stems on either side, a couple of more inches. The purpose of piling that soil up is to ensure that any potatoes that form near the surface of the soil don't get exposed to light, turn green, and then accumulate those glycoalkaloids that you don't want to eat. In general, you should aim for a broader peak rather than really sharp one.
You don't just have to cover up potatoes with soil. You can also use straw to cover up potatoes. Just put them in the bottom of a furrow. And either put some soil on and then use straw as the mulch, or if you want to, you can just put straw on them-- quite a bit of straw, mind you. It helps if the straw doesn't have any weed seeds in it, because rodents come in, initially eat the seeds, and then eat the potatoes. But if you manage to pull this off without covering the potatoes at all with soil-- the seed pieces-- then your potatoes will be soil-free inside the straw.
You can also cover up potatoes with black plastic mulch instead of straw. Black plastic mulch helps to warm up the soil so your crop comes up earlier. If you greensprout your seed pieces-- I mean leave them out in the sun, which keeps the sprouts short-- for a week or two before putting them in the soil, that also speeds up how long-- accelerates the time to which you can harvest your crop.
And you can also start potatoes from true potato seed. So potato scientists distinguish between seed potatoes, which are tubers, and true potato seed, which are botanical seed that form in fruit. If you haven't seen potato fruit, they look just like tomato fruit because potatoes and tomatoes are closely related. And there's the picture of some.
You can either-- well, typically, if you collect seed on a plant that you haven't deliberately fertilize-- pollinated like plant breeders do, it'll be a self. The plant will have selfed. And potato exhibits inbreeding depression. And the yield of the potatoes that you get from the seed will be less than the plant you started with.
Each of these seeds-- in distinction to the question you asked before if you're planting tubers. Each of these seeds is a genetically distinct individual. This can make it fun. You can make crosses so that you end up with white potatoes, red potatoes, and purple potatoes all showing up from your seed.
But there's a big drawback in starting with true potato seed. Actually, there are two big drawbacks. One is that there is no uniformity in the crop. Of course, that could be what you're aiming for. But if each plant matures at a different time, it's a bit of a pain to decide when you're going to harvest, for example.
So this is just a photograph of true potato seed after it's been dried. And you can also buy from some companies pelleted potato seed. So it's easier to work with. And you can plant an individual one.
The other big disadvantage to growing potatoes from potato seed is that it takes a lot longer to get a crop. So you have to start them indoors, just like tomatoes. You can't wait until you'd normally plant potatoes and plant one and hope you're going to get a decent crop. So you'd treat them like you would tomatoes. Start early growing them indoors and transplanting outside if you'd like to try that.
The big advantage-- and this is of planting true potato seed compared to tubers-- is that most viruses are not transmitted through true potato seed. So in some developing nations where viruses are a problem and labor is really cheap, they'll plant TPS. But most of the world plants tubers. And there's just a picture of some little potato seedlings.
So for the most part, potato breeders-- and there are only about 12 of us in North America. We're about the only people who work with potato seed and potato seedlings every year. My program plants-- well, not this past year. But generally, 20,000 to 30,000 of these every year.
A question often comes up when you work with potatoes is, oh, wouldn't it be cool to graft a tomato on top of a potato? And you can get tomatoes on top and potatoes underground. So this is nothing new. Luther Burbank was doing it 100 years ago.
For the purposes of the book, my dad did it, just to illustrate what happens. Oh, this is a tomato plant grafted onto the potato variety Kennebec. This picture's in the book too. And so is the next one.
SPEAKER 4: Are there potatoes developing in the pot?
WALTER DE JONG: Well, you'll see that in the next picture. So the tomatoes did OK. But the potatoes, that's pretty much a bust.
So the bottom line is the plant only produces so much photosynthate. And the tomatoes seem to be winning the battle. Tomatoes also don't, apparently-- aren't sending that much tuberization signal down to tubers.
So in terms of scale, this is the bottom of the stem. That's not very big. So the yield was-- by the time the tomato shoots were dying, the yield was not good. So there are companies that sell kits, you know.
Nice idea. But it just doesn't work so well in practice. I admired my dad for doing it.
So I've already mentioned one disease in potato that's a real nuisance. And that's common scab. Common scab, by the way, there's no chemical treatment for common scab. Well, actually there is, but none that you could use.
The only one I know of is you can fumigate your field with tear gas. And some farmers do it. But it's expensive, a few hundred bucks an acre. It's nothing we can do. So if you have common scab, you're stuck with disease resistance or bust.
Two other serious threats in potato are late blight and Colorado potato beetle. In North America, I guess these would be the big two that can completely hammer your crops. So if you're going to grow potatoes, I thought you should at least know what these look like.
If you find a potato plant with brown lesions surrounded by a light green halo, that's probably going to be late blight. If you look on the underside of a leaf when it's moist and the area that corresponds to the light green halo is sporulating-- you see this white, powdery stuff. Yeah, that's late blight that you have.
Late blight spores can travel great distances. And if it's cool and prolonged wet, that's perfect conditions for late blight. There is now a nationwide network that monitors where late blight is that you can-- USA blight, I think it's called if you Google it.
You can sign up. And they'll send you emails about where late blight is located each week. This isn't in the book because this network only formed in the past few months, as far as I know.
And you can find that, uh-oh, late blight has been found in Pennsylvania or western New York. My time is nigh. If you do find late blight, probably the best thing you can do is just kill your vines, chop them with a weed whacker or something. Or let them die. Leave the potatoes in the ground for at least two weeks.
And the reason you do that is so that any tubers that have become infected will just rot. They're just gone. And what's left, you can eat. If you find it too early, well-- I mean, if it happens too early, you just lose.
Late blight is devastating. It can completely wipe out your crop in a week. There's no doubt about it.
In terms of resistance, there is some. Later maturing varieties tend to be better. But there's nothing that's highly resistant to late blight.
Colorado potato beetles are voracious and promiscuous pests. If any of you grow potatoes, you've probably seen potato beetles. And you'll often find them in this pose. It's not hard to find them like this.
They will completely devour your plants. If you don't control them, within a few weeks, all you'll have left is stems. I've seen fields like this in Russia-- just completely defoliated. Those were peasant fields. That was kind of sad. I've also seen them in experimental plots, which that's fine, but when you're trying to eat them.
Particularly for home gardeners, this isn't actually too hard to control. You just look for them, and pick them off, and crush them, or put them in soapy water. But you also have to make sure you get rid of the eggs. You'll find them on the underside of leaves. They look like this.
And also get rid of the larvae, which look like this. You'll typically see an awful lot of these, hundreds on your plants. And your leaves will be disappearing quickly if you haven't gotten them early enough.
One cute way to control, or at least to reduce your problems with Colorado potato beetle-- potato beetles overwinter in the soil during the winter. And they can't fly when they come up in the spring. All they can do is walk.
So if your garden location has changed, you can dig a trench and put black plastic in the trench. I guess it doesn't have to be black.
And the potato beetles will walk toward the potatoes. And they'll fall in the trench and land in the plastic. And then they can't crawl out again. It's just great. And they just die in the bottom of the trench.
You can also use, early in the season-- I want to say a flame thrower-- a propane torch. If you singe the plants, not enough to kill the leaves but enough to-- you can burn the legs off the beetles. And they fall off.
This is actually used commercially. I'm not-- they'll pull a big flame thrower that can-- well, a torch over many rows simultaneously as a way to reduce the levels.
Oh, the number of ways to kill potato beetles is-- [LAUGHS]. My predecessor-- not my predecessor. Ward Tingey was an entomologist at Cornell who just retired last year or the year before. I forget when. And his talks at potato meetings were always well-received by the growers because he would describe the new modes of action of insecticides for potato beetles.
He talked about one which paralyzes the muscles in potato beetles. And basically, they'll bite. And then they can't let go, which for some reason, potato growers really warmed to that idea.
One last story, and then I'll stop. Maybe my favorite story in the book deals with one way that potato-- I'll just jump into the middle. It turns out, during the war-- there were some wars between France and Prussia in the late 1700s.
And it was observed by the powers that be that potatoes were a really useful crop to have. Because if an army came through and burned all the grains, you lost all your food. But if they tried to burn the potatoes, well, you still had the tubers underground. So it was to your advantage militarily if, at least, you planted some potatoes.
So there was the fellow, Antoine-Augustin Parmentier, who ended up being a high official in the court of Louis the XVI and Marie Antoinette. And he wanted to encourage the people on the outskirts of Paris to grow potatoes. And he thought he couldn't convince them just by telling them to grow potatoes.
So he adopted a different approach, which was to plant a large field of potatoes and then have a heavily armed presence, heavily armed guard monitoring the field day and night throughout the growing season. And at the end of the growing season, he asked the guard to leave.
So the people who were in the surrounding areas thought, ooh, something in there is really valuable. Let's go steal it. And they did. So that's just one of the small ways in which potatoes' adoption was increased in Europe and led it to be so widely grown today. So that's all I have to say.
SPEAKER 1: This has been a production of Cornell University, on the web at cornell.edu.
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Walter De Jong of Cornell's Department of Plant Breeding gives an overview of successful strategies for growing potatoes in a variety of conditions. His October 13, 2011 talk was part of Mann Library's Chats in the Stacks series.
De Jong is co-author of "The Complete Book of Potatoes: What Every Grower and Gardener Needs to Know."