Battling Tomato Late Blight

 Note to readers: I wrote this to add to information in the SF Chronicle Article that will appear in the print version of the paper on March 4, 2012. The article will not be availabe on until Monday, March 5th, so if you are here on Saturday or Sunday, and want to find out what is in the original Chronicle article, check back on on or after Monday.

Are you losing tomato plants to tomato late blight? This disease has been killing tomato and potato plants in the Bay Area for several years, and I have been trying to find tomato varieties that will resist it. I reported last year’s trial in the SF Chronicle and on (If you haven't seen that articlet yet, you can find it at .) In that article, I promised more details here, in my blog, so here they are. (Note: If you are an expert reading this post, and have corrections or more information to offer, please comment or send me an email through my website at

            This is a long post, so I will tell you what is in it here at the beginning. The first section explains what late blight is, with photos of symptoms. The second section is a brief explanation of ways to try to reduce late blight damage in your garden. Section 3 tells you how to set up a tomato variety trial yourself, with photos to show you how we did it. The fourth section includes some details about genetic resistance to late blight among available tomato varieties, with photos of the fruits of the ones that succeeded in the 2011 trial. The fifth section tells you how to send samples of your blight to the website in order to identify the clonal line(s) of the blight present in your garden. Then, finally, at the end of this post, is the list of varieties that also appears in the column, showing you which I trialed in 2009 and 2011, plus a few new varieties that I haven't yet trialed.

What is tomato late blight?

            Tomato late blight is caused by the oomycete Phytophthora infestans. (Oomycetes are organisms that used to be called “water molds.”) The disease-causing organism is in the same genus as the one that causes sudden oak death, Phytophthora ramorum, though the two diseases infect different groups of plants.

            “Tomato late blight” is a common name. Because the same organism also infects potato plants, it is sometimes called “potato late blight” or even “tomato and potato late blight.” It can also infect petunias, which are in the same plant family; though I have never heard it called “petunia late blight.”

            The words “late blight” are found in the common names of other plant diseases that are caused by different disease organisms. For example there is “celery late blight,” which is caused by the fungus Septoria apii. (Just one more example of why it is important to know the scientific name of a living creature, even if you commonly use the common name.)

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The first symptoms are darkened areas, briefly topped with white fuzz. This lesion is on a potato leaf.

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If a plant is sucseptible, lesions start to appear all over and spread, killing leaflets, whole leaves, and stems. If fruit has formed, it soon has greasy, brown "shoulders." If it ripens at all it wil have poor flavor.

            The tomato disease that causes our grief is known as a “late” blight because the symptoms typically show up only when the plant is mature, the fruit has set, maybe even some has begun to ripen. (By the time it shows up, we have usually had a couple of months to tend the plants and eagerly monitor the progress of setting fruit, so our disappointment is even deeper than had the disease struck early, before we had developing fruits to mourn.) The late onset happens because the mild temperature and moist air that encourages the spores to grow is likely to occur later in the summer, and also because as infections start to occur, there are more spores to blow about in the air and spread the disease.

            It’s important to know that the spores are not in the soil, but are blown in the wind from plant to plant, from as far as several miles away. They also are not carried in seed.

            It seems that we are fortunate, if that is possible, considering the damage this disease causes if it strikes, because so far, we have only asexual zoospores in our part of the world. These zoospores do not survive in soil, only in living or recently living susceptible plants. Because of this, we can get most of the spores out of our gardens by making sure we have no living plants that can get the blight in our gardens for four months in the winter. In our community garden, we remove all living and dead material from tomato, potato, petunia, and wild solanums (nightshades) from the garden in November through March. (If you do this, you also have to watch for and remove volunteer potatoes that can come up in winter and sometimes get late blight during a warm spell in winter and early spring.) While removing susceptible plants in winter can reduce the number of spores around in summer, it can’t, of course prevent new spores from blowing in, so you still may find the disease in your garden, but at least it isn’t a certainty.

            (If the form of the organism necessary for sexual reproduction were to find its way here, we could have sexually produced oospores here that would survive in soil and live longer than the asexual zoospores. Fortunately, there is no sign of this having happened or immediate expectation that it will.)

 Protecting Tomato Plants from Late Blight

            To protect plants from this disease, gardeners try to keep leaves dry, shelter plants from spore-bearing breezes, or spray them with a protective substance. In the Northwest, tomatoes are often grown under row cover (polyester fabric that lets most light through) or plastic hoop houses to keep rain off. In the Bay Area, we aren’t likely to have rain in summer. Our high humidity can provide enough moisture for the spores to germinate, but you may as well avoid wetting the leaves when you water, and you can try putting plants under cover if you like.

            Fungicides based on copper compounds and the fungicide Serenade are both registered to prevent tomato late blight and are permitted to organic farmers. Either kind of fungicide needs to be sprayed starting from the time you set out your transplants, and continued all season following label instructions, which are to spray more or less weekly. If they are used heavily, copper compounds can increase the copper content of soil so much that plants grow less well, so perhaps they aren’t the best idea. I did try spraying a copper fungicide one year. I found it a lot of work to spray my small planting so many times—and the plants still got late blight.

            I haven’t tried Serenade for late blight yet. It is based on the harmless soil bacterium Bacillus subtilis, and it is worth a try if you don’t mind the spraying. (I was able to prevent onion downy mildew from overtaking my perennial “walking onions” by spraying them with Serenade, so I do know that it works against that disease--another one listed on its label.)

 Looking for Resistance to Tomato Late Blight

            In addition to the winter clean up, which is basic to prevention, I have been trialing varieties that might stand up to this disease. I would very much like to grow my favorites, such as ‘Cherokee Purple’ or ‘Old German’ heirloom varieties, but they get late blight. I am looking for varieties that are resistant to late blight because I’d rather have some tomatoes for sure than spend all my time spraying or covering my plants and likely still losing them to the disease.

            The history of my tomato variety trials is in my sfgate article, ( ) along with a summary of how to do such a trial. Here are more detailed instructions for those who might want to carry out a trial.

            To do a trial, you need one or more experimental varieties (ones you have some reason to believe will resist the blight) and one control variety (one you know will get the blight). The control variety is there to prove that the disease was present in your garden, because if it wasn’t, you didn’t prove the experimental ones would resist it. I have been using ‘Celebrity’ as a control plant. It is an early hybrid that has short plants and resistance to quite a few diseases, though not to tomato late blight. You could choose another control, or could duplicate my choice to stay as close as possible to experiments that have been done already.

            The more plants of each variety you can use, the better, since you don’t want an accident, such as a broken stem or a virus attack to wipe out your one plant of a particular variety, and you want to know that your result is true in more than one plant (though because hybrids are more or less identical, what is true of one plant is more likely to be true of another than if you are groiwn heirlooms). I try to have at least 2 plants of each variety; use more if you have lots of space.

            Now you will have two goals. The first is to give all of the varieties in your trial as close as possible to the same conditions, so that resistance or susceptibility to late blight is the only difference. If you can’t treat them exactly the same (for example, you can’t grow them in exactly the same spot in the same year) you will randomize that aspect of their conditions. Your second goal is to keep track of what happened and record it. This you will do by making sure you know which plant is which and by recording whether the blight struck each plant over the course of the growing season.

            Start seeds for all of the varieties in your experiment on the same day, to ensure that they will be at the same age. Label each kind with a tag that gives the date you planted the seed and the name of the variety. When they have a couple of true leaves, pot them all into individual 4” pots on the same day. Make sure each 4” pot has a label with the date of planting, (date of potting up is optional) and the name of the variety. Don’t lose track of your varieties!

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On planting day, all of the plants are the same age and have been treated the same as they grew. Each pot includes a label.

            Choose a place to plant your experiment. Give the plants adequate space. We had 3 rows of 4 plants each in 2012. The plants were about 18” apart, the rows 3’ apart. Prepare the soil of the entire area in the same way. That is, spread any organic amendment or fertilizer evenly and then dig it in. If you plan to set up a drip system, set it up over the entire bed so that all the plants will be evenly watered by it. We used a half-inch tubing down the long side of the bed and quarter inch drip line with emitters every 6 inches. We ran two of the emitter lines along each planted row, one on each side of the plants.

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Spread organic soil amendment and any fertilizers you plan to use evenly on the bed and turn soil once to dig them in. Shown digging is David Elhami.

            Wait until mid-April or early May to plant out your seedlings, so the air and soil have warmed nicely. On the day you plant, have handy a hole-punch, twist-tie, paper and pencil. Before you plant, randomize your planting, as follows:

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Essential for setting up a tomato variety trial are hand-operated single-hole punches and twist-tie, for attaching labels to individual plants.

            Choose the seedlings you are going to plant and write the name of each on a small piece of paper. If you have two of each variety, make two paper names for that variety. Fold all of the papers up to conceal the names and draw names at random. (I like to draw them from a garden hat as a sort of joke, but you can draw them from whatever container strikes your fancy.)

            Make a map on a note pad. Start at one corner and make x’s to mark where the plants will be. Start in one corner, and as you draw names, write them on the map—progressing across the row and starting on the next row until you reach the end. With your randomized planting, you will reduce the chance that differences from one side of a bed to another, such as shade or wind patterns will throw off your results.

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This photo shows the making of the randomly arranged map. I draw variety names from an actual hat, just for fun, but you could use any container. Shown, left to right, are Donna Mandel, Pam Peirce, and Ken Jacobs.

            Now plant the tomatoes in the arrangement described on your map. As you plant each one, use the hole-punch to punch a hole in the label and use a piece of twist-tie to fasten the label to the main stem of the plant. be careful not to make it too tight. You want room for the stem to get a little thicker without being strangled.

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A labeled plant, with the label attached to the main stem. Make sure the twist tie is loose, so the stem can thicken a bit before you move the label higher on the growing plant. Note driplines on either side of the row.

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Here is the entire planting on the first day, April 16, 2011.

            Water well when all of the plants are in the ground, and water as you would tomatoes normally from then on. Probably best not to sprinkle water on the plants after the first day, but on that day it can reduce the chance of wilting.

            As the summer progresses, you will have three goals: 1. Keeping track of which variety is which, 2. Supporting your plants, and 3. Recording what happens vis a vis late blight.

            In order to keep track of the varieties, every 2 or 3 weeks we removed the hole-punched labels and moved them higher on the plant. We were careful that they were on a main branch, so it would remain clear which plant each was on, and so that we didn’t lose track of them when a small branch or leaf died. Of course we did have the map we made as a backup, but is nice to be able to see which plant is which at a glance.

            In last year’s trial, we supported the plants using the chainlink fence that was at one side of the bed, tall bamboo stakes and jute twine. We tied the twine to the fence, then wrapped it around stakes along each tomato row, then tied it to a stake at the end away from the fence. We used two pieces of twine per row, one on each side of the plants. As the plants grew, we used more twine at higher levels.

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A section of a row showing how two lengths of twine are used, one on each side, and how it is wrapped aroung stakes at intervals along the row to support the plants. This was shot on May 18th, 2011.

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Here is the planting on July 13, 2011. Nice tall green plants, but two weeks later, the damage had begun.

            Periodically, we observed to see whether late blight had appeared. We didn’t stick to a strictly regular schedule, since we weren’t interested in the exact progression of the disease, but did check every 3-4 weeks, and were able to tell which plants died first and which had fruit set, etc.

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Here I am, on August 11, 2011, recording relative damage to the plants. Note the plant label, which has been moved higher on the plant twice to make identification fast. The plant with the label is 'Golden Sweet'. The still-green plant behind me is 'Defiant PhR'.

            Need I say that, other than watering at ground level to keep leaves dry, an ordinary precaution I would always take when growing tomatoes, I didn’t take any measures to prevent or avoid late blight? I didn’t put them under cover or spray them with anything. In fact, I grew the trials in locations where late blight was definitely a problem in the previous year, just to be sure my experimental varieties had something to resist.

The Genetics of Tomato Late Blight Resistance

            There are two aspects of genetics that affect resistance. I am not going to be able to explain them in great detail here, but here are a few facts. The first aspect is the genes that provide the tomato variety with resistance.

            In last year’s trial, I grew 4 varieties I obtained from Johnny’s Selected Seeds. Rob Johnston, the founder of that seed company, told me that two, ‘Golden Sweet’ and ‘Plum Regal’ had one gene that provided resistance to late blight, and they were heterozygous for that gene. That is, it was on only one chromosome of a pair. The other two varieties, ‘Mountain Magic’ and ‘Defiant PhR’ had two genes that provide resistance. They are heterozygous for these genes, meaning that each of them appears on only one chromosome of a pair.

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'Golden Sweet' died in my USF planting, but I did get fruit in my community garden, in a warmer microclimate, and where we have been taking out susceptible plants in winter to reduce the number of spores in the garden. The fruits are small, but were indeed sweet.

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'Mountain Magic' was alive, with some damage, at the end of my USF planting. It set some fruit there, but only ripened a few of the fruits it set. In my community garden, it ripened plentiful fruit. The fruit is about 1 1/2 inches in diameter and has an average flavor.If you look carefully, you will see a couple of brown stems, lost to late blight damage.

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'Defiant PhR' had only minor damage at the USF plantng, but didn't set fruit. However, in my community garden, the one plant had 9 pounds of fruit. Size varied, but the biggest was over 3 inches across. This is a beefsteak-type, meaty fruit, with good, though not excellent flavor.

            In my trial, the ones that were heterozygous for two resistance-endowing genes fared better than the ones that had only one of them. Johnston says when varieties have been bred that are homozygous for these genes, that is, have them on both copies of a chromosome pair, resistance should be even better.

            I don’t have details about the genetic reasons for resistance of other varieties, such as ‘Juliet’ or ‘Legend’. The only other fact I can relay is that some wild tomato types have resistance through different mechanisms than the above. Examples are some cherry tomatoes and currant tomato, which is a different species than most tomatoes.

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In 2011, 'Juliet' died at USF, but in 2009 and 2010, it produced fruit in trials in my community garden. This fruit is smaller than an average past tomato, but larger than a plum tomato. Flavor is good, not great, but production is very good.

            The second genetic aspect, the other end of the resistance equation, is that the late blight organism is not genetically uniform. The correct term for the variations are “clonal lines.” They are clonal because they reproduce asexually, thus they are identical to their parent organisms. Why are there different ones? Presumably due to mutations that appear from time to time. There have been 24 clonal lineages in the US, but some may have died out. In any given year, there may be 4 or 5 active ones.

            I have made slow progress on tying tomato variety resistance to clonal lines of the late blight organism. I do know that ‘Legend’ resists US3 and US11. And I know these aren’t the clonal lines we have, because ‘Legend’, touted as a breakthrough in late blight resistance, dies first in my trials.

 What Clonal Lines do We Have?

            When I realized that resistant varieties may have resistance to specific clonal lines of late blight, I saw the importance of finding out which clonal lines we have in the Bay Area. Until recently, I was having difficulty finding this out. The breakthrough this year is locating the website . This USDA-funded project is a national consortium of late blight researchers. They don’t know what clonal lines we have, but they want to know!

            You can help find out by submitting samples of your infected plants. Do this by going to the website and clicking on “reporting outbreaks,” then on “first time registration.” Register now so you will be sent a copy of the APHIS permit you will need in order to submit samples, since they will be shipped across state lines, to a lab in Oregon. Once you have the permit, you will be able to print copies of it to include with your samples. They prefer leaflets that have blackened lesions, but which have not yet wilted, and would like at least five examples in a sample. You register your sample online, so you will get a sample number to write on the sample bag before you send it, and can then use that number to track your results. You also print out a sample submission form to include with your sample, and write the sample number on that too.

            Full directions are on the website. I encourage you to look and register now, so you will be ready when the disease shows up.

A List of Tomato Varieties You Might Like to Try

            Here is a list of varieties I have trialed, plus a few I haven’t yet, as reported in my Chronicle/SFGate column, follows. (See that article at for full trial results.) My best results so far have been with ‘Juliet’, ‘Defiant PhR’, ‘Mountain Magic’ and, in a warmer SF microclimate, with ‘Golden Sweet’. As seed sources for varieties listed below, start with Johnny’s Selected Seeds and Totally Tomatoes.

Note: Numbers (i.e. “70-75) indicate days from transplanting to first ripe fruit under normal conditions, though San Francisco plants may be slower. Det=Determinate or short plant. Ind=Indeterminate, or tall plant. These varieties are listed in order of fruit size—smaller to larger. For more information, such as flavor and other disease resistance, see seed catalogs.

*in my 2009 trial, **in my 2011 trial, ***in both trials

*Currant tomato—70-75, Ind, fruits under ½”, avail in red, yellow, and white. This is Solanum pimpinellifolium, a different tomato species that has some resistance.

*Matt’s Wild Cherry—60, Det, fruits marble-sized, red, some resistance.

*Tommy Toe—70, Ind, ½ -1” round red, fruit, some resistance

*Koralik—61, Det, 1” fruit, round red, some resistance

Red Pearl—58, Ind, 1 oz. oval fruit, said to have intermediate resistance

**Golden Sweet F1—60, Ind, oval, grape-sized yellow fruit, moderate resistance

**Plum Regal F1—68, Det, 4 oz., oval, red fruit, moderate resistance

***Juliet F1—60, Ind, 1½-2 oz. oval, red fruit, in clusters, moderate to good resistance

**Mountain Magic F1—66, Ind, 2 oz., red fruit in large trusses, good resistance

**Defiant PhR F1—70, Det, 5-7 oz. round, red fruit, good resistance

***Legend—70, Det, 4-5 inch, round, red fruit, poor resistance in my trials.

Ferline F1— Ind, 5 oz., round, red fruit, listed as “tolerant” of late blight.

Old Brooks--70, Ind, large fruited, said to have “superior” resistance

Please do write me if you have questions or any results to report. You can send me email at or write a comment into this blog.

Fava Bean Rust

This is a plant with a severe case of fava bean rust, or Uromyces viciae-fabae.

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No, the plant is not oxidizing. Rusts are plant diseases that give the impression of rusty spots, but really those are pustules (great word eh?) containing fungal spores. Most of the fungus consists of threads called hypae that are all tangled through the plants, robbing them of nutrients in plant sap. The spores released at the surface are ready to float away and find a new plant to infect. Here are some close up shots of the spore pustules:

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I see the disease fairly often in San Francisco gardens. It does probably reduce production somewhat, but it often occurs later in the season, after most of the crop has formed. Here are some ways to lessen your chance that it will occur or reoccur:

--This disease is encouraged by wet leaves, so try to water favas at the ground level, rather than sprinkling them. Of course we can't prevent rain and misty weather, but the less dampness the better.

--If you see the disease early, with only a bit of damage, you might slow it by removing diseased leave, though of course you don't want to take too many leaves off of the plant.

--If your plants are ripening beans, you will be reluctant to take them out until you harvest, but as soon as you can do so, take th plants out. Do not compost them. In San Francisco, you can put them into a green bin for Recology to compost, since their compost gets very hot and should kill the spores. When you take your plants out, pick up all the fallen and dried leaf debris you can find as well.

--Don't save and replant seed that came from infected fava bean plants.

--Copper sprays, which are approved for organic farmers, may offer some control. However, they will be a lot of trouble for a small planting, and will harm the soil if used repeatedly.

--A two to three year rotation might help, but if your garden is open to breezes from nearby plantings, the spores may be reintroduced.

(See also on this blog posts on chocolate spot disease and the black aphid that infests fava beans.)

Disease of Fava Beans--Be Very Afraid

Recently I saw a disease on fava beans that was unfamiliar to me. It wasn't rust, which makes rusty brownish pustules on leaf undersides. No, these were nasty brown spots on the leaves that merged, became almost black, and destroyed the leaves. My diagnosis is chocolate spot disease, which is caused by the fungus Botrytis fabae.

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Here is an early stage. Then the spots merge and darken. The leaf below is on its way out.

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Notice the tear in the middle of the leaf, caused by dead tissue.

I don't have a description of this disease in any book, though one, The Self-Sufficient Gardener, by John Seymour, mentions that "horse beans", the smaller favas farmers feed to livestock, are more susceptible to it than the larger ones humans usually eat. This book is an English publication, and favas are an Old World native bean, so it is probable that they have had some fava diseases longer than we have.

Be that as it may, when I read the Wikipedia article here, I realized this disease could spread fast once it appears. The spores can be carried on or in the seed and can also form resting bodies that lay in wait in the soil until you plant the next fava bean crop. It can also survive "in crop stubble and residue." (That's the cut stems and all the fallen leaf debris you forget to gather up when you take out the diseased plants.)

When the spores germinate, the lesions begin to appear, and within 4-5 days, new spores are released to infect new leaves, stems, or flowers. These spores blow in the wind to new plants or in splashing water. The spores and disease are most active in cool, humid conditions, which is what we've got much of the time here in SF.

So if you have seen this disease on your fava bean plants, take those plants out as soon as you can. Take the whole plant out, roots, fallen leaves, everything. Do not compost it in your garden, though the SF Green Bin is generally OK for diseased plants, since their process is very hot and thorough. Do not save seed from these plants. It should be OK to eat the beans that aren't disfigured by any lesions. This fall, try to avoid planting favas in the same place you used last year if they were infected. Get fresh seed, and look for varieties that have shown resistance. (I will look for some--no idea where to find 'em yet. Send a comment in if you find some, please.)

Another web page says that this disease was first documented in California in 1998. It was found near the coast, no surprise, considering its adaptation to cool, damp weather.

I suppose that farmers who aren't farming organically use fungicides that organic farmers wouldn't use. What would I use? I notice that the label of Serenade fungicide includes both "vegetables" and the plant disease genus "botrytis," so I think I'd give it a try.

Serenade, which is permitted to organic farmers, has as its active ingredient the common soil bacterium Bacillus subtilis. This organism colonizes the plant surface, I've been told, preventing other microorganismns from getting a spore-hold. You spray it on plants weekly. They recommend spraying on a small part of the plant first to see if it will harm the plant. You can apply it up to the day of harvest. (This is not a recommendation, just my thoughts on what I might try and why. As with any pesticide, read the label for yourself before you buy, mix or use it and follow the directions carefully)

However, as with any plant pest, it would be quite unwise to try to control it using a chemical. If you have seen this disease, I repeat: Get those plants out of your garden. Rotate to a new site for favas. Don't save seed. Help me locate some resistant varieties. Then, if you had this disease this year, and have planted fresh seed in a new garden location, next fall, you might try spraying the plants when they are young, before any disease has appeared, to try to prevent an outbreak.

By the way, our favas have not had this disease, I am happy to report, and we've been eating young fava bean pods, when the seeds are still small, roasted in the oven according to a recipe that appeared in the SF Chronicle a few weeks ago. You roll them in olive oil, add salt and pepper, and roast at 450 degrees for about 25 minutes. Sprinkle with more salt, eat pods and all. Serve as a side dish or just before a meal. You may have to pull strings off the pods, but they sure are good!

Tomato Trials 2011

That mean old late blight strikes every year in my community garden and when I am foolish enough to think I can grow tomatoes at City College, so I am still on the lookout for a late blight resistant variety or two. Inland gardeners may escape this nasty disease, but it is thriving in cooler gardens near the coast.

Two years ago, in a trial reported in this blog, I grew several varieties that "someone" on the web said resisted late blight where they garden. Not a very scientific choice, but for several years, I tried the ones that wholesale seed companies and universities have been developing for resistance and none of those worked, so I was ready to try anything.

As a review, tomato late blight, which is the same as potato late blight, and which caused the Irish potato famine, is not soil borne, but carried by aerial spores from infected plants. It appears rather late (as in late blight) in the season. There are dark brown lesions on stems and leaves, followed by general collapse of the plants.Here are a couple of photos of plants with symptoms:

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The fruit may start to show the greasy brown coloration near the stem while it is stil green, or after it ripens. This may spread to whole fruits. In any case, fruit on infected plants ripens poorly and isn't sweet.
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The one variety that has been on the market for several years is 'Legend'. In my trials, it was the first to die. Here is the miserable dead plant of 'Legend' in 2009:

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Of the others I tried in 2009, my best plants were 'Juliet', which now is sold with a notation that it has some resistance to "Blight." (Not very informative, since there is also an early blight, a disease much more common in the Eastern US, but an entirely different disease.) Here is 'Juliet' in 2009:

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Although 'Juliet' had a touch of late blight, it produced a huge crop of these plum-type fruits--bigger than a cherry tomato, but smaller than a standard paste tomato. They were, however, perfect for the Broiled Tomatoes with Herbs and Cheese recipe I printed in Golden Gate Gardening.

In the past couple of years, late blight has been appearing on the East Coast as well as in the West. A few more supposedly resistant varieties have appeared, and I am trying 4 new ones:

Plum Regal F1 (Salsa/Sauce/Drying) 68 days

Golden Sweet F1 (Yellow Grape) 60 days

Mountain Magic F1 (Red, tall vine) 70 days

Defiant PHR F1 (Red, short vine) 70 days

So, I got them all from Johnny's Seeds, who may or may not have seeds of them left this year. They are all hybrids, and all relatively early. (The number of days doesn't count the 6 weeks or so to grow transplants, but anything under 75 is reasonably early.) The one I am most hopeful for is 'Defiant', since it has a formal "PHR" after the name, stands for "Phytopthora Resistant". (Phytopthora is the scientific genus name of the late blight fungus.) 'Defiant' is also said to resist 2 strains of the disease, so maybe it resists the strain we have while others didn't?

The plants will be potted up this week, planted out in May in one or possibly several San Francisco test sites. Stay tuned!


Another Year in the Life of An Apple Tree

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Our apples at their best.

In the ongoing saga of our apple tree, a tree of unknown variety but good fruit and usually good production, another harvest is past. This year we finally got rid of the woolly apple aphids, after two years of spraying the insects with rubbing alcohol (right out of the bottle) weekly and 2 commercial canola oil sprays each winter on the dormant branches. Because the insects spend part of their time in the soil, we also used the canola oil pesticide as a soil drench twice each winter, watering before and after we sprinkled it on the soil surface (an off-label use the idea for which  I got from reading research reports about the pest in the East ).

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Woolly apple aphids make huge galls where they suck sap from the branches, as they have done here on this pruning cut (not on our tree, thank goodness!). They are reddish aphids, but are covered with a white waxy fluff.

 We also think it helped that we discovered the trunk had been buried a foot or so deep yea all these years, since before we bought the house, and unburied it. A buried lower trunk is really bad news for any tree.

But because we were paying so much attention to the woolly apple aphids, we forgot to spray sulfur to prevent scab, the disease that makes surface blemishes on the apples. We were also lulled by the dry early spring into thinking that scab wouldn’t be a problem this year. The early-setting fruit did fine—no scab. Then the spring turned wet, and the later-setting fruit was attacked by scab. (Our tree is borderline for getting enough winter chill, so sometimes it blooms over a long period.) Some of the later forming fruit was so affected that it was stunted and malformed.

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Some of our apples with scab disease. Note damage to leaves from the disease as well.

However, overall the tree became so vigorous (when liberated from the extra foot of soil and freed of the stem and root sucking of the woolly apple aphids) that we wanted to be sure to give it a summer pruning to curb its excess growth. But the summer was so cold and foggy that the tree seemed always to be wet. So we put it off, hoping for a dry day. That day came, Lisa pruned the tree, and boom, we had a heat spell. So some of the apples developed sunburn on their southeast sides—big round black sunken blotches.

 Then came October 15th, the usual ripening date, but most of the fruit was clearly not ripe. it was still green under the red streaks, very hard, and had its flat, starchy, unripe flavor. Now, in mid-November, it is finally getting ripe. Many of the fruits do have some scab, and a few (not as many as it once seemed) have the sunburn, which will prevent them from keeping well. But overall, there is more than we can eat, as usual, so it’s off to the Free Farm Stand (after our friends and neighbors have been given as many as they can use). And off to bake pies. I photographed the making of an apple pie and plan to put the photos, with recipe, on this blog in a day or two.


Syrphid fly in my backyard garden

Last week I was out early in the morning when a spiderweb hanging between a chair and a columbine was still decorated with crystalline dewdrops, each one a rainbow. I was checking what was coming into bloom, when I noticed a handsome sryphid fly on a potato plant. It was still sluggish from the slight morning chill, so I thought maybe I could get a photo. I ran up to bring down my camera with a close up lens, and lo, it was still there. So here is the my best shot.

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I am always glad to see a syrphid fly, because their larvae eat aphids and other soft-bodied insects. This particular syrphid fly is a bit smaller than a honeybee. It looks kind of like one, but those markings are just to fool a predator. You will see syrphid flies hovering around plants, like little helicopters. Because of the way they fly, they are sometimes called hover flies, and because they hover around flowers, they are also sometimes called flower flies. They may be striped or may be single-colored, and may be much smaller than this one, but by their hovering shall you know them.

Look closely at the insect, and you will see that it has only 2 wings. That is characteristic of flies, which are in the insect order Diptera (di=2). Most insects have wings, and all the other ones have 4. 

A couple of weeks ago I gave a talk at a garden club in the East Bay. It was outdoors, in a garden, so instead of bringing a show of photos, I brought some vegetables and vases of flowers, some edible, others to attract beneficial insects. As I was talking, a syrphid fly came along and checked out the flowers. It considered seriously the collard flowers in the bouquet of edible flowers, but rejected them and settled on the parsley flowers in the vase of flowers to attract benificials. Point well made.  

Tomato Trial Results

This is 'Juliet' the winner in production and tomato late blight disease resistance in last summer's tomato trials. Of all the varieties I grew, it had the best production and withstood the blight the longest. It is a hybrid, and indeterminate (tall) plant. Juliet green 08 copy It was advertised as "grape" type, but the fruit was much larger than a grape, as you can see in the photo below, often reaching 2" long. It was just right for quartering lengthwise and adding to a salad or for halving lengthwise

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to stuff and broil as an appetizer. Not a really great flavor or texture, but OK and far better to have lots of OK fruit than 3 or 4 really good ones followed by death of the plant, as happened in the following case. 'Green Zebra' is an heirloom with fruit that is green when ripe, with yellow strips. This is how the plant looked by the time the 'Juliet' was in full production:

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This 'Green Zebra' grew to about a foot and a half, bore 4 ripe fruits, then died, while the 'Juliet' reached 3 1/2 feet with probably a couple hundred fruits. The photo below is of 'Legend', the variety bred to resist tomato late blight at Oregon State. It was actually the first to die. So much for the theory it was resistant!

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I think we have a strain of the fungus that it can't combat.

So what of the others I planted? 'White Currant' bore second most fruits, though they are very small, and had somewhat more blight damage than 'Juliet'. It is another indeterminate plant. It is very rangy, reaching its branches out far from the support. The fruit has a somewhat different, intense flavor, that some liked, and others found too surprising. There are also red and yellow versions of currant tomatoes, but I happened to get the white (which is really pale yellow). All are supposed to show some blight resistance. I thought they would be tiny, but many were the size of smallish cherry tomatoes. They were nice in salads.

The point of my trial was to grow varieties that anyone, someone on the net, a seed company, another gardener, claimed to have resisted blight. Another of these was 'Koralik' a determinate cherry-type tomato, an heirloom from Russia, that Territorial Seeds said seemed to have some resistance and to be early and productive for its size. These plants had more damage than 'Juliet' but did do relatively well.

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They were a standard cherry size and flavor. Nice, though not remarkable.

Another, 'Tommy Toe' showed similar resistance. It is a taller plant, but not as productive. The fruits are round, and a bit larger than most cherries. They were as wide as the fruit of 'Juliet', but round rather than elongated.

'Matt's Wild Cherry' was the last of the tested varieties. It did have a crop, not much bigger fruits than the currant tomatoes, not as strong a flavor, some blight damage.

All of the above was at Dearborn Garden in the Mission, which is relatively sunny. The following images are from City College of San Francisco, where I had a second planting. Here it is colder and damper, so when blight is present, it does more damage. I did get some good ripe fruit from all trial varieties except Legend, but by the end of the season, all were suffering.

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I think this is 'Tommy Toe', with typical brown fruit and brown stems caused by blight.

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Here is 'Juliet'. The fruit toward the back has typical browning, and you can see that the stem to the left is still green, but the one it joins is brown and so are the leaves.

 So what to do next year? Any other tips out there? Are there any other varieties you've found to have a vestige of resistance? Otherwise, I guess at least I'll have some tomatoes next year from 'Juliet' and one of the currant types.

All you tomato gardeners, if you had any blight this year, and your plants are still in the ground, get out there and rip them out. Pick up every fallen leaf. Do not compost the dead plants. Don't replant until April. This gets rid of last year's spores. More may blow in. The disease is airborne, not soil borne, but at least you aren't harboring it over winter. Take out peppers and eggplants and any leftover potato shoots too.

Finally, I will share a sign I saw in my communty garden. The gardener said he'd been in a demo and happened to have it along, so he thought he'd display it:

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Tomato Late Blight Report

In March, I got seed for a number of tomato varieties that someone or other said might resist tomato late blight, the awful disease, spread by airborne spores, that has been killing a lot of tomatoes in the California Bay Area for about 15 years. (and has recently been killing East Coast tomatoes as well) I planted some of them at City College, and some in my Mission District community garden. I also planted 'Stupice' tomato as a control--a plant I know gets late blight, just to be sure it's around.

The plants are bigger at City College, probably because the soil is in better shape. There are only a few blight lesions here and there on the plants. They ripened a few fruits in July, but a long foggy period in mid July through early August has meant a break in ripe fruit for now.

At Dearborn, more fruit is ripening, due to the warmer microclimate. I have lost one plant to late blight, and it is a 'Legend' tomato. This variety was bred to be late blight resistant, but clearly can't resist the strain, or the plant pathologists call it, the race, of late blight we have here. The plant is now only a couple of brown stalks. Some of the other plants have some blight lesions on stems or leaf stems, but are still bearing. The best looking plant, good color, lots of fruits, and no sign of late blight so far is one called 'Juliet'. If this one proves resistant, I will be realy pleased, because it makes nice oval fruits, like paste tomatoes but smaller, and lots of them. They are bigger than a cherry tomato though, about 1 3/4 to 2 inches long. Flavor--not too great, but they worked really well to make broiled appetizer tomatoes last night.

(Recipe: Mix 4 tablespoons of finely chopped green onions, 4 tablespoons of grated parmesan cheese, 4 tablespoons of mayonnaise, and two tablespoons of finely chopped Italian flat-leaf parsley. Cut 6-8 small tomatoes in half. Spread/mound the cheese mixture on the halves. Broil 2-3 minutes or untill the high places on the topping just begin to brown. Serve hot as appetizer or side dish. This recipe is in my book Golden Gate Gardening.)

Anyway, I promise photos soon. And welcome any reports or photos from others who may be growing any of the varieties we grew at City College last spring.

Plum Problem--Scars on Fruit

PlumProblem72 copy Here is the photo that went with my SF Chronicle (and column last Sunday. I'll bet it looks fine on the website, but in the paper it was in B&W and was printed so low contrast that you couldn't really see the damage on the plums. So for those who couldn't make it out, here it is. Those scars were caused by a leafroller, a caterpillar that is the larva of a moth.

     What was interesting to me is that when you see photos of the damage this caterpilar causes, you always see either the caterpilar or the damage it does to leaves, rather than fruit damage. It is the sleuth symptom, never considered important enough to show, so always a mystery to most of us.  

     I have seen damage like this for a long time, on various fruits, and nary a photo anywhere that was captioned to explain what did it. My dad called them "bee stings", though we both knew that wasn't right. Thank you to Anita Crotty, who took this photo and asked what caused the damage. And thank you to Dr. Paul Vossen, who filled me in on the cause of the scars.

     Apparently the caterpillar feeds on young leaves, making a bit of webbing to roll a leaf around it to hide from predators. If the leaf is next to some very young fruit, the caterpillar nibbles a bit of that too. If ignored, the problem can get worse every year. If you see these scars one year, you can prevent the insect from overwintering on your tree by using a dormant oil spray in January or February, before the buds begin to open, or, failing that, using some Bt spray when you see tiny caterpillars, about when the tree is in flower.


Tomatoes Planted for Late Blight Trial

Today I finally planted the last of the tomatoes for the tomato late blight resistance trial. I have some at City College and some in my community garden. Three other people I know of are planting them together as a trial, one in Berkeley, one east of the hills in the East Bay, and one in Moss Beach. I'm wondering if anyone else who purchased the plants at the City College plant sale has logged onto this blog to read about the trial. If you did, please send a comment, so I know you are out there.

Now there is nothing to do but wait. Late blight is, as the name shows, usually late. That is, it will show up after the fruit has set and is ripening. To succeed in this trial, all the plant has to do is stay healthy. I will be taking pictures as the summer progresses.

For more on late blight, do a search in this blog. Try "tomato disease" for a link to some very good photos of the disease.