Disease « The Yellow Farmhouse Garden

November 16, 2017

Three impressive tomato varieties

Filed under: Disease,Vegetables — bob @ 12:12 pm

Earlier in this past growing season I took an informal survey of how a number of tomato varieties were responding to leaf spot diseases. You can go back and read the post to find out how things were going for them at that time.

I kept an eye on them through the season and watched their progress. In one garden I applied a couple of sprays of an organic fungicide, that didn’t seem to make much difference; it may have helped if I kept it up. As expected, on all of the plants, sprayed or not, the leaf spot symptoms got progressively worse as the fruit on the plants began to grow and develop. It takes a lot of plant energy to produce a crop of tomatoes.

A curious thing happened on one variety at the end of the season. The heirloom variety, Granny Cantrell, began to shake off the fungal infection. While the other tomato plants lost pretty much all of their leaves and most of them actually died back, the Granny Cantrell plants shed their infected leaves and grew very healthy looking replacement leaves. That was something I’ve never seen in a tomato plant. Sure, many varieties struggle to send out more leaves but they never seem to amount to much. Not only were they growing leaves but they were also ripening existing fruit and producing new tomatoes to boot! Our growing season is too short for the plants to continue to grow so I’ll never know if the new shoots would have continued to grow without leaf spot symptoms. It may be a useful trait that tomato breeders could use to develop a new variety.

Notice the new green foliage on the Granny Cantrell plant on the right compared to the defoliated tomato on the left.

Juliet was another noteworthy tomato. They had good resistance to the diseases throughout the growing season and produced a huge crop of tomatoes, far out pacing any variety I grew this year.

All of the tomatoes I grew were tasty, how could they not be? since they were vine-ripened and eaten right after picking. All the people who tasted the tomatoes; and there were quite a few, agreed that Cherokee Purple was their hands down favorite. Cherokee Purple however, had little disease resistance and didn’t produce very many tomatoes at all. They also have very thin skin making the very hard to handle without damaging them. They are not a typical red tomato so their coloring made it harder to distinguish when they were ripe. Also their flesh inside has a distinctive purple hue that, along with their taste makes the quite memorable.

Bob

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July 19, 2017

Tomato disease scores

Filed under: Disease,Vegetables — Tags: disease spots, spots on tomatoes, tomato disease, tomato disease resistance, tomato spots — bob @ 7:15 am

This is the time of the season when tomato plants start showing signs of disease infections, usually as different shapes and colors of spots depending on which particular disease has infected the plant.

Last week I took an informal survey of several varieties of tomatoes to see how each variety is holding up under early disease pressure. My MO was to look for leaf spots on the plants. I made no attempt to identify which disease was causing what spots. Then I ranked them on a scale of zero to ten depending how bad the plants looked. Zero meaning no spots were visible, ten meaning severe symptoms. No plants were bad enough to score what I imagined to be ten.

I didn’t count how many leaves were infected; or measure how many square centimeters were discolored; or brix levels of leaves; or levels of ethylene gas; or any other scientific criteria. Heck, I didn’t even alphabetize the list of varieties. I ignored any cultural differences such as mulch, staked or caged plants, planting history, etc. .Over half were heirloom varieties, some of those looked quite good compared to the modern ones.

I surveyed about fifteen gardens in two different locations about 20 miles apart. I made a point to look at them all the same day because twenty four or even twelve hours could mean the difference between no spots and spots. Here’s a chart of what I came up with:

Tomato variety	Plant score
Brandywine	3-6
Belarus	0-1
Cherokee	1
Juliet	0-1
Sheboygan	0
Pruden’s Purple	0
Granny Crantrell	1-2
Super Sweet	3
Belstar	3
Pink Honey Drip	3
Roma	4-6
Yellow Cherry	5
Large Red Cherry	6
Early Girl	3-5
Rainbow Blend	3
Roma Type	7
Beefsteak type	6-7
Brandywine Pink	6
Moon Glow	3-4
San Marzano	3
Bobby’s Girl	0
Chadwick Cherry	0-1
Unknown varieties	5-6

Pruden’s Purple, by far looked the best it has no spots and very vigorous leaves. Chadwick Cherry came in a close second. There were a few different beefsteak-type tomatoes that were not specifically tagged by variety but all of them had more advanced disease progression.

Keep in mind this is only a snapshot of conditions for one day. That could all change later on as the plants begin to get stressed by fruit production.

Bob

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August 25, 2016

Powdery mildew on pumpkins

Filed under: Disease,Pesticides,Vegetables — bob @ 7:36 am

Growing pumpkins and squash has changed sine the early days early days of my career. Back then, pumpkins rarely had any problems whatsoever. You could just plant some seeds, keep the patch weeded and you were pretty much guaranteed a fine crop.

This year demonstrates how times have changed. In addition to the squash vine borer and squash bug that I talked about the last couple of weeks, we are now seeing powdery mildew on our pumpkins and squash.

Powdery mildew shows up as a white powdery-looking coating on the surface of the leaves. It eventually cause the leaves to turn yellow and die. Under certain conditions it will eventually kill the entire plant.

We’ve had textbook weather conditions for the development of powdery mildew. This type of mildew is a fungus that thrives when daytime temperatures are high and nighttime temperatures are low enough to form morning dew.

Some varieties of pumpkins and squash are more resistant to powdery mildew than others. Here are two different varieties growing side by side.

Unlike most other fungi, powdery mildew does not need liquid water to infect a plant and grow. High humidity within the leaf canopy provides the environment powdery mildew requires.

We do not see much powdery mildew during rainy years. As a matter of fact, one non-chemical approach to controlling powdery mildew takes advantage of this. Spraying the surface of the leaves with overhead irrigation will wash off much of the infection. It also will cause existing spores to absorb so much water that they burst, greatly reducing the source of new infection. This method only works if the area is well drained, otherwise you will end up causing other problems due to excess water.

Commercial chemical and organic formulas are available on the market to control this disease. I’ve been using a homemade concoction that has been working pretty well for me. I mix one table spoon of baking soda and two tablespoons of Murphy’s Oil Soap to a gallon of water. Spray it onto the leaves no more than every seven to ten days. It’s important to use this ratio, a stronger solution will damage leaves.

The spores from the species of powdery mildew that infects the squash family of plants does not survive Michigan winters. Spores are blown in to Michigan on southerly winds each spring to start a new cycle of disease.

Powdery mildew is very species specific, meaning each species of plant is infected a specific strain of fungus. For example, the powdery mildew that infects lilacs cannot spread over to squash and vice-versa.

This, I hope, will be the last problem we’ll have to deal with on our vine crops this year.

Bob

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April 28, 2016

Chamomile tea helps protect young seedlings

Filed under: Disease,Seed Starting — bob @ 7:11 am

In my last post we discussed damping off, a fungal disease that attacks and kills developing seedlings. A clean growing medium will minimize the occurrence of damping off. And a seed starting mix can be pasteurized by pouring boiling-hot water through it.

Once the seeds have germinated and the newly emerged plants are off to a good start, there’s more you can do to protect those tender seedlings.

There’s plausible evidence showing some homemade concoctions can inhibit the growth of pythium, the fungus responsible for damping off. One of these is chamomile tea. That’s right, the same tea we brew when we feel like mellowing out with something warm to drink.

Steep at least two teaspoons of chamomile flowers into each cup of boiled water. Let the tea come to room temperature before straining and using. This is quite a bit stronger than what most people use to brew a cup of drinking tea. The stronger you make the tea the effective it is.

Chamomile grows wild in some gardens. Every year we collect chamomile for tea.

Use a spray bottle to water your new seedlings by spritzing the tea over the plants and soil once a day. To help the tea be more effective, make sure you allow for plenty of air movement around your plants while they are growing.

Eventually Mother Nature will take over and you won’t need to use the tea anymore. As seedlings grow and get older they will outgrow their susceptibility to damping off.

Bob

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March 31, 2016

Use boiling water to protect newly sprouted seedlings against damping off disease

Filed under: Disease,Seed Starting,Soil — bob @ 10:50 am

Growing your own transplants from seeds is a very satisfying experience and can save you money too. However it is not without it’s problems. Just about every gardener who has started plants from seed has a story to tell of watching a crop of seedlings just starting to make good growth then all of a sudden the plants shrivel at the soil line, fall over and finally die.

That is a symptom of a condition known as “damping off”. It also kills newly sprouting seeds under the soil giving the impression of a low germination percentage. The gardener gets the wrong impression that he’s planted a batch of bad seed when in reality it’s damping off.

Damping off is most commonly caused by a soil based fungus called Phythium, but Rhyzoctonia and other species of fungi can cause similar problems. Whatever the case, it is not curable.

It’s an insidious disorder. The seedlings can look sturdy and strong then suddenly,bam! overnight an entire tray of seedlings will be lost.

Most of the time you can avoid damping off by purchasing a fresh bag of sterilized soil-less seed starting mix. Sometimes however, even a new bag of starting mix can harbor the fungus, although that is pretty rare.

When Pythium shows up, it’s probably the gardener who contaminated the mix by using dirty tools, pots, or even the potting bench. All tools and containers need to be scrubbed clean with a detergent. To be doubly sure, the items can be dipped into a 10 percent solution of household bleach.

Although all plants can be infected, some species of plants are more susceptible to damping off than others. For example petunias are prone to the infection.

A six inch pot is a good size for less that thirty or so seeds.

Whenever I start a batch of expensive or hard to find seeds and don’t want to take any chances of losing those precious seedlings, I take the extra step of re-sterilizing the starting mix. Some might say I’m being extra cautious but sometimes seeds are irreplaceable and need all the protection we can give them.

For small amounts of soil, I pour boiling water through a pot of starting mix — then go back and do two additional pours. If you decide to try it yourself, be sure to place the pot in a spot where the water can drain through easily. I like to do this outside on a wire rack rather than in the sink.

This boiling water method has been used by gardeners for a long time and has shown to be pretty effective. Since the entire volume of the soil mix will not reach 212 degrees Fahrenheit — the temperature at which it would be considered sterile — this could be considered more of a pasteurization method rather than actual sterilization technique.

Bob

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