During the past couple of weeks I saw a lot of gardens having problems with tomato plants not producing fruit. When discussing this problem with gardeners, the first thing I hear from them is usually,” I’m growing lots of leaves but no tomatoes”. Then they go on to attribute it to an overabundance of fertilizer of one sort or another.
Nutrient imbalance may cause problems, but this season it is likely due to the extended hot temperatures we had until the break in the weather happened this week. Temperatures in the mid-nineties can damage tomato blossom causing them to fall off the plant — no blossoms means no tomatoes. This phenomenon is known as “tomato blossom blast”.
There is really nothing we can do to prevent flower damage when the temperatures are so high except wait it out. Now that the weather has moderated, our tomato plants will start producing more blossoms and setting more fruit.
If another heat wave occurs, it’s likely we’ll see another round of tomato flower blast.
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.
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.
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:
Pink Honey Drip
Large Red Cherry
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.
Regular readers of this blog know that I like to talk about the idea of growing near-organic apples.
With the near-organic method, you spray as little as three times early in the season when the apples are still very small — starting when they first begin to grow. Then two more sprays are applies spaced about ten days to two weeks apart. If it is rainy during that time period, then another spray may be needed. After the third spray application, you stop spraying. By the way, I sometimes do a very early pre-blossom spray.
I use a general, all-purpose orchard spray mix, one with both fungicide and insecticide in the formula.
The reason why this technique works as well as it does is because it takes advantage of the life-cycles of orchard pests. Generally, the insects that cause the most damage to apples emerge early in the season. The spray knocks back the population of pests. Then once the spraying is over,the population of beneficial insects begins to grow and help keep pests in check. At least that’s one theory I’ve heard.
Through the season, as the apples grow in size, pesticide residue is washed off with the rain and breaks down in the sunlight, hence the name “near-organic”. There is no official term as “near-organic” but it helps to describe how the apples were grown.
The apples often have some discoloration due to harmless fungi on the outside surface of the skin. I just wash off what I can (or rub it off on my shirt) and eat the apple whole.
I’ve been using this method for many years and have had great success with it. It’s not a guarantee that it will work in your situation but it would be worth a try if you are aiming to reduce your use of pesticides while still having half way decent apples.
I certainly would not recommend it for someone who’s livelihood depends on their apple crop, but for a few trees in the backyard, it may be worth trying.
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.
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.
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.
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.
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.
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.
One of our gardening goals is to grow as much as we can for Thanksgiving and Christmas dinner, I bet you do that too. Even if we end up with only enough servings for just Thanksgiving dinner, I call it a successful harvest.
Judy needed to come up with a dessert for Thanksgiving this year so she decided on homemade-from-scratch, gluten-free apple cobbler. Of course you need apples for apple cobbler so I went to my storage bin for the apples.
They were not the pristine apples I usually have, these were covered in small, unsightly spots. I’ve seen those symptoms before in years past. They had “cork spot” sometimes called “bitter pit”.
To me, cork spot is a more accurate description than bitter pit. For one thing, apples don’t have a pit, they have an apple core. The other reason is because of the corky appearance and texture of the affected area. On the other hand, the spots do have a bitter taste, so “bitter pit” works too.
Some scientists separate bitter pit and cork spot into two different disorders with the difference being the timing when the spots show up. If they show up before harvest, it is cork spot. If it develops in storage they call it bitter pit. Either way it is not caused by any disease organism or insect.
Even though the disorder may not show up until Thanksgiving time, it has its beginning way back during the growing season when the apple was still on the tree. As the apple grows, there is some competition for water between the developing fruit and the growing leaves. That water competition may cause a calcium imbalance which weakens the cell wall in the fruit leaving it open for the symptoms to develop.
Pruning, of course, has a big effect on the number of leaves on a tree. So the proportion of apples to leaves can be different from year to year.
Rain or lack of it determines the amount of soil moisture available and that can change almost weekly during the growing season. So it is a complex set of events that contribute to the problem which is why you may not see it every year in your home grown apples.
Improper storage will often lead to bitter pit. In my case, I’m guessing it was because I did’t get the apples into storage quickly enough. That can cause the spots to show up before you have a chance to use the apples.
I had a few different varieties of apples in storage and some apples had spots and others didn’t — some varieties are more prone to bitter pit than others.
The corky texture of the spots made it much harder to peel the apples. Also, I ended up with smaller pieces because I had to cut away the affected area to get rid of the bitter taste.
Judy’s apple cobbler turned out great and was a big hit at the dinner, you couldn’t even tell it was gluten free!
I spared everyone from the convoluted story about the apples and their bitter pit spots.
While picking my sweet corn this year, I’ve noticed a higher than normal amount of ears with corn smut growths.
Corn smut is a fungal disease that infects all types of corn but sweet corn is most susceptible to it. The fungus invades the corn tissue and causes the corn plant to form a gall-like growth. We usually see these growths on the ears of the corn but they can also occur on the tassel and other parts of the plant.
It’s just about impossible to eliminate corn smut. The fungus can live year after year in the garden soil and will reinfect a sweet corn crop each season. Plus the spores of the fungus is easily carried by the wind from infected plants.
There is no spray or seed treatment for this problem. The usual control suggestion is to cut out the infected plants and burn them before the smut has a chance to form spores.
This year however, I’ve decided not to fight corn smut but instead embrace it.
South of the border — I mean Mexico, not Ohio — corn smut is a delicacy. Since smut is a fungus, it is used much like mushrooms which are fungi too. Some people call it Mexican truffle, in Mexico it’s called huitlacoche. Mexican farmers, instead of destroying the infected plants, harvest the growths and sell them at a premium price.
My corn smut is past its prime — it’s filled with dried spores — so I didn’t have chance to try it yet. I have one more crop of sweet corn coming on and I’m looking forward to my huitlacoche harvest!
Another potential disease problem is over the horizon threatening our local trees. This time it is the Black Walnuts that are at risk.
A fungal infection called Thousand Cankers has been killing Black Walnut trees in the western part of the United States for several years. It has been confined to nine states in the Rocky Mountain area and westward until July of this year. Its range seemed to be associated with a different walnut called the Arizona Walnut. Black Walnut is not native to that particular area but was brought in and planted by arborists, landscapers and others.
This summer it was confirmed that the disease had spread to at least one location in the Eastern USA, Knoxville Tennessee. Scientists now believe that it may have been present there for a number of years without anyone knowing about it.
At this time Thousand Canker disease is NOT present in Michigan.
The disease is caused by a fungus which is carried by a very tiny beetle called The Walnut Twig Beetle. Despite its name the Twig Beetle attacks larger branches or even the trunk of Black Walnut Trees by tunneling under the bark. They leave small “galleries” or tunnels in the wood caused by the beetle larvae feeding there.
When the larvae mature into adults they emerge from the branches out of small holes chewed through the bark. The fungus then infects the damaged area and causes a small lesion or “canker”. These cankers spread very fast and merge together eventually moving from the outer bark into the cambium layer. Each branch has a tremendous number of cankers which is how the disease got its name.
The cankers themselves are often difficult to see and identify. A special lab test is needed for positive identification.
There is no cure or control for either the Twig Beetle or Thousand Cankers, plant pathologists are working on that though.
In the meanwhile we can help slow down the spread of this problem by not moving firewood just like we do to prevent Emerald Ash Borer from spreading.
There is no federal quarantine on moving wood products but the State of Michigan has issued its own quarantine against shipping articles made of wood from certain western states.
The USDA Forest Service has a good publication on this problem.
As I mentioned earlier, Thousand Cankers is not present in Michigan at this time. Keep in mind that there are a lot of other things that can cause a tree to show signs of die-back other than this disease.