More Food Shortages? Phytophthora Fungus Infects Vegetable Gardens Across the Country

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by Jayne Rising

Shortages seem to be the theme of 2020 and 2021. Everything from meat to commodities and even semi-conductors made the list of possible or definite shortages. Now, the early onset of a fungus that attacks vegetables could leave us with no pumpkin pie at Thanksgiving and no Jack-o-Lantern’s at Halloween!

What is Phytophthora?

P. capsici blight, unfortunately, has hit pumpkins early and hard this year, endangering the supply of commercially canned purée as well as jack ‘o lanterns. “Home gardeners may also see it affect their ability to grow tomatoes, peppers, cucumbers, and squash.” [source] P. capsici: infects pumpkins and other cucurbits, bell peppers, and eggplant.

Phytophthora, classified as oomycetes, is a fungal genus with 170 described species and another 100-500 estimated waiting for discovery. Phytophthora is one of the water molds, and not one species is up to any good in garden or field.

P. infestans is the bug responsible for the Irish potato famine of the 19th century and is a severe problem in potatoes today. Members of this troublesome genus (listed below) infect the Solanaceae family, including potatoes and eggplant, cucurbits including squash and pumpkin, strawberries, and many economically significant trees, flowers, and shrubs.  P. parasitica attacks bell peppers, tomatoes, and eggplant. This infection is commonly called buckeye rot.

This article includes general information applicable to pumpkins, potatoes, tomatoes, strawberries, and peppers, common vegetables grown in home gardens. The source links throughout this article have pictures, which are, of course, handy to diagnose. 

General signs and symptoms of infection for pumpkins and potatoes

Here is a condensed list of general symptoms of infection to help with spotting and diagnosing.  

General First Signs: Water-soaked spots are small, pale to dark olive green, angular to irregular, and present on the lower leaves at the leaf tips or edges. Lesions rapidly expand into large, dark brown to purplish-black dead areas during cool, moist weather.

Early Fruit Infection Symptoms: Lesions are grayish-green or brown, showing where the fruit touches the soil. Buckeye rot lesions have a smooth surface with a diffusely defined margin. Late blight lesions develop a rough surface and sharply defined margin.

Potato Tuber Symptoms: Lesions are small to large, irregular, slightly depressed, red to brown, or steely purple surface. A tan to dark reddish-brown, dry, granular rot extends into the tuber.

Cucurbit Fields: This infection usually appears first in low areas where soil remains wet for an extended period. Crown rot causes the entire plant to collapse and die. Water-soaked lesions are dark olive in the beginning and become dark brown in a few days. [source]

On pumpkin specifically, it affects the roots, stems, leaves, and fruits.

General signs and symptoms of infection for strawberries, peppers, and tomatoes

Strawberry Root Rot: The outer root cortex remains white while the inner core or stele turns a pinkish-red color. After a few minutes of exposure, healthy root tissue turns reddish. [source]

This site also includes interesting information on laboratory diagnosis in addition to specific root rot symptoms. You will find detailed information on useful fungicides and a fertilizer regimen for management as well. 

Leather Rot on Strawberries: occurs during flowering or after fruit set when wet conditions and berries contact the soil. Infected blossom clusters turn brown and die. Immature fruit, infected areas appear brown to black. Mature fruit the color of infection ranges from light tan to light red or green, and the fruit becomes hard and leathery. [source]

Leather rot is currently an issue for me. The amount of Captan I used to get even a couple of big bowls worth is appalling. I can’t imagine eating the rotten fruit. It is that horrid looking.

Root Rot in Peppers: A few pepper varieties are resistant to the root rot phase of the disease but are susceptible to the crown rot phase. Varieties that are resistant to Phytophthora blight: Paladin, Aristotle, Declaration, Intruder, Vanguard, Hechicero, and Sequoia. [source]

Infection in Tomatoes: Also caused by P. capsici and called buckeye rot, similar to cucurbits and peppers. [source]

Life Cycle

The pathogen overwinters in infected tubers and diseased plants and adores cool, wet conditions. Nights in the 50s F with days in the 60-75 F range and high humidity over a 4-5 day period are highly conducive to blight development. Not only does the fruiting body of Phytophthora (sporangia) form thick-walled spores that can survive for several years (oocytes), it procedures spores are motile (zoospores.) Meaning they swim. And the zoospores last at least five years. 

Management 

Crop rotation is crucial. Plant resistant varieties if possible. However, be aware resistance can decline over time. Resistant varieties are also likely to require some fungicide. Avoid planting susceptible hosts in fields where Phytophthora has been for at least three years. If irrigation is the chosen watering system, irrigate in the early morning, so the leaves dry quickly. Avoid using surface water as your source since it may carry spores.

Planting in raised beds with black plastic mulch helps drain water away from the plants and keeps fruits from direct soil contact. However, be aware that water can pool under the plastic and help spread the infection. Increase fungicide coverage on individual plants by widening the rows and reducing the number of plants in the field. 

Minibeds on Plastic consists of several 30″ by 30″ small raised beds made of wood, spaced approximately 18″ apart and constructed on top of a plastic mulch barrier. The plastic inside the wood frames is cut out and removed and used as mini planting beds. Plastic over the area surrounding area holds moisture in the soil and prevents weeds from growing.

Sanitation is also a powerful preventative technique. Remove diseased plants as well as the plants adjacent to them. Burning or burying them may be your best option. Power wash equipment that’s been in a Phytophthora-infested field. If you’re using hand tools, bleach is your friend.

Fungicides: There are a number of these labeled for use on Phytophthora. Consider a combination treatment because the fungus has developed resistance to some of them, Mefenoxam, for example. As I said, this is a nasty genus and highly aggressive. 

Are there more shortages headed our way?

Phytophthora blight is a nasty disease with a substantial economic impact. It’s challenging to eradicate, so prevention is your best defense. Even with treatment, my strawberry beds produced much less than usual. There is clear evidence that I’ll be treating my garden next year as well. 

Perhaps this is a great time to learn how to grow pumpkins! 

Have you had this disease infect your garden? Were you able to successfully manage it? Did your garden survive? Share your diseases in the garden stories with us in the comments section.

Special thanks to https://twitter.com/jdeezy2k3 for the tip!

About Jayne

Jayne Rising is a gardener and bookworm with a BS from the University of Wisconsin and a Master Gardener certification. She’s been growing food on her small urban lot since 2010 and teaching others how to do it since 2015. She’s involved in a number of local urban agriculture initiatives, working to bring a sustainable and healthy food system back into the mainstream.

More Food Shortages? Phytophthora Fungus Infects Vegetable Gardens Across the Country
Jayne.Rising

Jayne.Rising

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21 Responses

  1. it does seem to be my problem this year with my Blue Hubbard squash. They started great and then when harvested, imploded. collapsed in on itself. Rotted from within. None were edible.

    I’m in southern middle TN.

    1. I am so sorry that happened to you! Phytophthora blight absolutely sucks. My strawberry harvest, as I said above, was a small fraction of what it should have been. This organism is everywhere and never up to any good. Hopefully this article will help you manage.

  2. I think this was my worst year EVER trying to harvest ANYTHING or keeping my garden ALIVE! I have fought bugs/worms I’ve never seen before, had all my tomato plants turn black & die & what few tomatoes I was able to salvage from pests got grayish-brown spots on them and rotted. I had squash vine borers that I’ve NEVER HAD BEFORE destroy all my zucchini, summer squash, spaghetti squash and some of my Cherokee Tan pumpkins. I planted my squash 3 different times, they would start producing and be lush green & healthy one day then the next would be wilted to the ground and dead. Nothing I did to stop the squash vine borers worked so I gave up. Cabbage moth worms destroyed my collards & kale & NOTHING I normally do to rid the problem worked this year. I try NOT to use pesticides and use organic methods to control pests. We had an unusually cool spring & very wet with so much rain we had reached our normal yearly totals by the end of June!! I am in coastal Alabama, grow zone 8b. Our spring came in January, TOO EARLY, so everything started WAKING UP early (onions, garlic, fruit trees) only to get hammered with a Polar Vortex in February (that hit Texas hard with the snow, ice & frigid temps). We got all but the snow so this affected my fruit crop since everything was in full bloom when the Polar Vortex brought temps in the teens to our area which is NOT NORMAL for us. Then the rain started and my pear trees got FIRE BLIGHT so I’m battling trying to save them even after a drastic pruning which caused me to lose my pear crop. My plum trees got TOO MUCH WATER from the rain and I lost two of them I assume from root rot but with torrential rains every single day I was not able to get to the orchard to discover the problem til it was too late. The only thing I was able to grow this year with success was Chambers bitter weeds and other weeds that took over because I was not able to keep the weeds at bay from all the rain. I did salvage some of my onions as they thought after the Polar Vortex and warm weather returned it was time for them to push themselves up & they fell over when just the size of marbles. I took a chance and pulled them, cut the tops off, replanted & they did come back but they were just as confused as I was as to WHAT THE HECK THEY WERE SUPPOSED TO DO…wake up and grow or go to sleep because they were ready to harvest, much too early. My onions were at best the size of lemons instead of oranges so I did get SOMETHING for all the work I put into trying to save them. I could go on & on with the continued problems I’m having this year. Summer garden is done except for SOME of my eggplants that survived, my sweet potatoes that won’t be harvested til late fall (in my area) and my okra. It was late to get going because of the cool weather we had during their peak growing but now that we are in a drought & heat advisories (heat indexes 110-115+(F) they are finally growing and producing. I am 65 yrs old and it is like I am having to LEARN ALL OVER AGAIN how to garden given all the weather anomalies, pests & temp’s not normal to our area. It is almost like SOMEONE OUT THERE doesn’t want us to grow food to survive the coming hard times. Over the last few years, I’ve had to go from planting what normally grows in FULL SUN to partial sun because full sun burns the plants to a crisp. Nothing is the same as it used to be in years past as far as gardening. I pity those that think they can just go buy seeds & plant them to grow their own food, that have never gardened before. What I have learned thru my YEARS of gardening is having to be REVISED to adapt to the changing weather. Guess I will get started on building that greenhouse as soon as it cools off some & hurricane season passes. Looks like there are several potential MAJOR HURRICANES brewing in the tropics and I don’t want to build my greenhouse just to have it blown into the next county if/when a hurricane hits (I’m in a hurricane-prone area that had a direct hit or brushed by several just last year). I will NOT GIVE UP because I KNOW it will be my lifeline for survival in hard times coming.

    1. It sounds like you’ve received a college-level course in plant pathology! I’ve had those too these last couple of years, and they’re interesting but a bit hard on the diet. Regarding the squash vine borers, some gardeners plant their squash around their life cycle so when the bugs are out, the squash isn’t. Have you tried that?

    2. I’m in Texas too and I am having a hard time with my bell peppers and cantaloupes look like they may have that fungus, not sure yet. It does seem like “something” does not want us growing our own food. My strawberries survived the freeze, but nothing else, and now they are not producing. We’ve had unusual rain up here in the part of Texas I am in and it’s literally soured my dirt, and so I am having to get another dump truck of fertilized soil up here. Then another problem we have is the insects, like weird worms that I have never seen before, just hanging off the trees that all of a sudden just went away. I am not giving up either because I am not paying $2. 89 for a pound of tomatoes and this garden is my and my families lifeline

  3. If the fungus requires wet conditions then its out of luck here this summer! My nemesis has been squash bugs. Nasty-looking insects that suck the moisture out of the squash plant while injecting into it a cocktail of injurious saliva that kills the entire plant. Its been a constant battle this year.

    1. It’s always something, isn’t it? Gardening requires constant vigilance and quick action when there’s problems. I had aphids on one of my bean plants last year. No beans from that one.

    2. We must live in similar areas. . . no moisture here either but the stink bugs completely wiped out my pumpkins too. I might get two little ones this year. Everything else is dead. The only way I’ve stayed on top of them in years past was to get painters tape and remove the eggs with that before they hatch. I kept them under control last year, but this year didn’t stay on top of it and lost almost everything. It’s been a rough one.

  4. Anchorage, AK has had a rather cool summer (I think less than 10 70 degree days), so even the ‘garden guru’ in our area is commenting about it being a bad year. Yesterday broke record for most water in a day, so whatever few things were coming along, done. I started pulling up things a few weeks ago, calling it quits & getting ready for winter.

    1. Ugh! I’m guessing that your growing season is even shorter than mine in Northeast Wisconsin, right? My plums blossomed in the early warmup, then we had a freeze during blossom and all of the set fruit later dropped off. Very frustrating! I’ve had that tree for 6-8 years and have yet to eat a single plum.

    1. I didn’t know what it was until this article. Thanks. Just about every one of my bell peppers got it here in NE Florida.

      I’m gone for a bit so we’ll see when I get home.

      1. Thank Daisy! She’s the one who sent me the idea. It’s a nasty organism though. I did an independent study on Phythophthora in oak and it was incredible. Good luck dealing with the bell peppers! I’d love to try the fertilizer regimen. Otherwise, it’s pesticides and those aren’t good for the garden past a certain point either.

  5. this is my first year gardening for real. just moved to a property in tennessee. squash bugs! some kind of white mold stuff on the leaves of the butternuts. Now I have discovered LDS prepper on you tube and bought the book he recommends. He uses minerals to strengthen his plants and seems to be really working out well.

    1. Jack, could the white mold be powdery mildew? Squashes and cucumbers are almost a written invitation for that. Powdery mildew is caused by different fungi and it’ll kill your plant eventually. It’ll also keep your plants from producing since it’s sucking the life out of them. Copper fungicide, considered organic as pesticides go, is the usual treatment. You can try neem or stylet oil but if your infection is advanced they won’t work. Basically you’re in a race to get what you can from the infected plants before they die. And try to keep it from spreading to your other plants! Ugh.

  6. Hey from South Africa! I saw the artilce about increasing fungal growth
    in plants across at Natrual Blaze) and link it in my mind with Clelste Solum’s view that plant fungi are in the shots to cause this problem. Borax is an anti-fungal and can be very diluted and used to counter this. Take care as it can also be toxic. I take a teaspoon in a litre of distilled water and then add 10 ml per litre to my distilled drinking water, to clear the metals from the pineal gland. Not sure how to use it for plants, though.

  7. No pumpkin pie for Thanksgiving? What a lot of people do not know is that the feds say that there only has to be 14% pumpkin in a can of pumpkin pie filling. I assume that the rest is squash.

  8. Remember when thousands of people all over the country were receiving unsolicited seed packets in the mail from China (at least that’s where they were believed to be coming from)? Many not so wise folks planted those seeds. I’m wondering if something was introduced intentionally to harm our food supply.

  9. I lost a 12×30 plot of a bumper crop of squash last year (2020) from this. I thought at first that it was just powdery mildew, but then everything was rotting from the inside out, even the vines. I pulled it all up & filled 5 of those big garbage cans (had to borrow 2 from the neighbor) with everything that i pulled up. I was so disappointed and upset. I treated the dirt with cinnamon instead of chemicals. Later added more compost/chicken bedding waste to make healthier dirt. Between the excessive rain and high temps, even in Michigan, it’s a wonder that anything survived this summer. Now I’m seeing signs in tomato plants that are in pots in what i thought was clean dirt. I’ve lost 2 of 10 tomato plants and 4 big almost ready tomatoes already. Ugh! Good thing i don’t depend on feeding my family with my gardening efforts.

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