Anti-fungal sprays during rainy times

[KathyDC]

Hi everyone!

DC gets pretty humid, which always gives me fungal issues with my tomato plants. I'm really trying to stay ahead of it as best I can this year, for now proactively spraying with Bonide Revitalize, which is a broad-spectrum anti-fungal, with the active ingredient Bacillus amyloliquefaciens strain D747.

I've been spraying about once a week, the last time was Monday I think. We are forecast to have about 4 days of sporadic rain starting tomorrow, and I'm wondering if it would be useful to spray in between if I get a window. Or maybe just spray tonight? Or both?

How do you usually handle rainy days with trying to control fungus?

[nathan125]

Have you tried using it as a soil drench?

[b54red]

You could use a copper spray. They work fairly well if it doesn't rain too hard and too often. If that happens the diluted bleach spray can work used every few days between rains but make sure to use it very early or very late in the day.

Bill

[KathyDC]

I have, yeah, but their directions for soil drench are basically right after transplant, after that it's to be used as a foliar feed. But I did do one right after transplant.

[KathyDC]

The one good thing about this rainy stretch is that the temps are low - in the 70s. Whatever this front is, has also depressed the heat. So I probably will go out maybe tomorrow night and hit my plants with some bleach spray, just in case.

[edweather]

That's always the rub, trying to keep plants protected during rainy stretches. I try to make sure they are sprayed before it rains, and maybe sneak a spray or two in between rainy days. This year the fungal diseases are the worst in 4 years since we moved to Georgia. Almost all plants are a losing battle now, but fortunately we have processed about 100 lbs of tomatoes into sauce already.

[KathyDC]

I managed to sneak in a spray tonight with Revitalize. Still haven't gotten the bleach spray out, only because while rainy, the temps have been under 80 -- so far. Tomorrow we hit 80, so I'll have to continue to look for windows to spray... looks like sporadic rain for the next week. Blah!

[cwavec]

Kathy,

I believe you are probably not using Revitalize to its best advantage. This
product is a bacterial slurry and does **NOT** have any immediate anti-fungal
effect. The bacteria have to first "colonize" the tomato leaves. Once they
take up residence there, they supposedly have two types of "MOA" (mode of
action - that's a technical term). First, the bacillus will directly attack
fungal spores, reducing them to a liquid (that's the liquefaciens part -
Latin, you know). Second, the colonizing bacteria induce the plants to develop
their own immunity to invading fungi. Look at the front of the bottle and you
will see that claim. The interesting part here is that said "immunity" is a
factor of the plant itself, not just something applied to the outside of it
that could wash off in a rain. If this is true, you should not have to worry
about rainy spells, as the plant's developed immunity should carry it through
such periods. Then, in good weather, you can re-apply your fungicide in
anticipation, at least partly, of the next wet spell.

A similar product, called Serenade, has been around for quite a while. I have
used it for over 15 years. It is now discontinued in "gardener-sized" packages,
although you could still buy it in 10 liter jugs. Strain D747 is another variety
of, essentially, the same bacterium. There have been some arguments over the
taxonomy of these two strains, with respect to whether they are or are not
actually the same species. In any case they are very close.

In spite of the publicity from Agraquest, the developer of Serenade, Bayer, the
owner of the brand since about 2012 and others, there are lots of questions
about the actual activity of the product. I am less familiar with D747 but still
have many of the same questions:

What does it mean for the bacteria to colonize the plant leaf?
After colonizing, how long does the bacteria stay there?
In what sense does said "immunity" exist?
How long does it take to develop?
How long does it last?
And many more.

During all the time I used Serenade, until a couple of years ago, I had not
much luck with it. I tried it by itself, in all kinds of sequences and combinations
with other products, and never saw much sign of any effect at all. Nonetheless,
the laboratory research seemed fairly convincing so I kept at it. In 2018, just
because I still had some left in the sprayer, I sprayed it on a plant that had
earlier been treated with another product, which was already severely infected
with early blight. A day or two later, I looked again and found that there had
indeed been a beneficial effect.

In 2019, I repeated my accidental treatment on a regular schedule. Result - no
foliar infection except for a short period in late summer. I had gotten a bit
lazy and had not sprayed for about 3 weeks in August. In addition, the degree
of success in early summer was so noticable that I almost wondered if I had done
something else. A few small lesions of early blight developed. One spray cycle
eliminated all these. In recent years my tomato plants have been essentially
dead by mid-August. In 2019, I put them to bed in October!

This year, I am trying again. My plants were set out in the first week of May.
They were treated with copper soap first. After planting out, they have been
treated weekly with the combination that I have indicated earlier. The result -
there is no sign of any foliar infection. This is in an area (Western PA) with
a climate also highly conducive to the development of foliar diseases and a
location that presents high risk of infection due to the presence of alternate
hosts and highly contaminated soil. This past week we had a period of rainy
and humid weather. I had the choice of spraying on a rainy Saturday
(my normal routine), a rainy Friday, a Sunday with 50% chance of precipitation,
a cool, wet Monday or of waiting for Tuesday when it was sunny, dry and 87
degrees. I chose the latter course to see if my plants would make it through.
They did. There is still ZERO sign of any foliar infection.


Any readers interested in trying my method (it involves a little more work)
should send me a PM and I will describe the procedure.
Comments, general questions, etc. may be posted in the thread

opened by KathyDC.

[cwavec]

Bill,
What kind of copper spray do you mean? There are several but only one that I respect.
Some copper products consist of almost pure copper oxide. And then there is copper
sulphate, which can be used to make a spray.


The important factor is to provide as many Cu++ ions as possible. If you look at, say,
some form of copper oxide, it is hardly soluble at all in water. Hence, a lot of copper
in your soil but hardly any Cu++ ions.


Copper octanoate, on the other hand, and increasingly popular, is hydrolyzed in water.
In other words, the ions are released into solution and there are lots of them while
the total metallic copper equivalent is only about 1.8%. This product is very good if
not perfect and is now found under many labels.


When used with a spreader sticker the effectiveness of copper octanoate is increased
stupendously. So much so that there is the risk of phytotoxicity. To avoid damage to
my plants, I never use more than 1 tablespoon (1/2 ounce) and the same amount of
spreader-sticker in one gallon of water. Recently, I have been decreasing that dose a
little without noticeable effect on performance. To measure such small amounts I use a
syringe to put 10-12 ml into a gallon of water.

[RayR]

Originally Posted by KathyDC

I managed to sneak in a spray tonight with Revitalize. Still haven't gotten the bleach spray out, only because while rainy, the temps have been under 80 -- so far. Tomorrow we hit 80, so I'll have to continue to look for windows to spray... looks like sporadic rain for the next week. Blah!

What fungal problems are you concerned about? Not all fungal pathogens are the same and Bacillus amyloliquefaciens strain D747 like any other biological is not going to be effective against all. The product is registered as a control or a preventative for certain pathogens either on the leaves and stems or in the root zone.
If you apply any bleach spray, you are going to kill the Bacillus you applied with Revitalize.

[cwavec]

**

"Bacillus amyloliquefaciens strain D747 like any other biological is
not going to be effective against all. The product is registered as
a control or a preventative for certain pathogens either on the
leaves and stems or in the root zone."
**



Ray,


You make some good points but not necessarily in the context of this
bacterial product.


First of all, I'm not sure about the product being "registered as a control
or a preventative". This is a complex topic but, as far as I know, most
fungicides, etc. are "listed" for use on certain crops. This does not really
mean they are very effective. In the case of Serenade, for instance, the
manufacturer initially claimed that it would control almost everything on
almost every kind of food-producing plant. As the years passed, they
had to back off a lot of it. In the case of early blight (and a few others)
they diminished their claim to the level of "suppression" whatever that
means. Bayer, having acquired Agraquest, has backed off even more.
They even effectively concede that if you want to control anything, you
had better use it with something else "in a regular spray program"



Now, anyone who actually used Serenade knows it really isn't much
good for anything, at least by itself. D747, I don't really know. It hasn't
been around as long in the US. I haven't seen a clear exposition of the
claims and haven't had a chance to use it myself. It's based on the
same ideas as Serenade but is the result of research in Japan.


Both Serenade and D747 have two modes of action. Neither product
is "going to be effective against all" in the sense that it contains
something that will have some action on contact with a pathogen.
They don't. So any expectation that either of them will help very
much in a transient situation such as wet weather or humidity is
pure fantasy.


What D747 (and Serenade) does is produce "colonies" of bacteria on
the leaf surfaces. These bacteria then fight the pathogen by producing
and releasing a class of compounds known as "iturins". These, you
could say, are directly effective against pathogens. They are the basis,
at least in part, of the original expansive claims of effectiveness. But
note - they first have to be produced by the bacteria.


The second MOA exists with respect to stimulation or induction
of the plant's own ability to resist pathogenic activity. Research
beginning in the 1990s indicated that such an ability does actually
exist and that it is translocatable. The journal Plantae* says it better
than I can:


"
Plants have the ability to increase disease resistance in distant,
systemic leaves after a local pathogen infection. This phenomenon
is called systemic acquired resistance (SAR), which is a long-lasting
and broad-spectrum resistance. Furthermore, SAR is a conserved
trait in various plant species and is important for agricultural practice.
Some mobile metabolites need to move from infected leaves to
distant leaves to establish SAR."
*

*https://plantae.org/a-positive-regul...ed-resistance/


So,with respect to "What fungal problems are you concerned about?, it
remains a valid question but when considering "effectiveness" we need
to remember that we are now concerned with what happens within
the plant itself and that lots of research is still being done. What does
"wide spectrum mean"? How long does it take to occur? How long
does it last? How about control or suppression of individual
pathogens? And remaining cognizant that SAR is a property of the plant
so that we need to think less about what is in the bottle and what
effect it might have in a few minutes or half an hour before it is washed
off in the rain.

[RayR]

Originally Posted by cwavec

**


You make some good points but not necessarily in the context of this
bacterial product.


First of all, I'm not sure about the product being "registered as a control
or a preventative". This is a complex topic but, as far as I know, most
fungicides, etc. are "listed" for use on certain crops. This does not really
mean they are very effective. In the case of Serenade, for instance, the
manufacturer initially claimed that it would control almost everything on
almost every kind of food-producing plant. As the years passed, they
had to back off a lot of it. In the case of early blight (and a few others)
they diminished their claim to the level of "suppression" whatever that
means. Bayer, having acquired Agraquest, has backed off even more.
They even effectively concede that if you want to control anything, you
had better use it with something else "in a regular spray program"



Now, anyone who actually used Serenade knows it really isn't much
good for anything, at least by itself. D747, I don't really know. It hasn't
been around as long in the US. I haven't seen a clear exposition of the
claims and haven't had a chance to use it myself. It's based on the
same ideas as Serenade but is the result of research in Japan.


Both Serenade and D747 have two modes of action. Neither product
is "going to be effective against all" in the sense that it contains
something that will have some action on contact with a pathogen.
They don't. So any expectation that either of them will help very
much in a transient situation such as wet weather or humidity is
pure fantasy.


What D747 (and Serenade) does is produce "colonies" of bacteria on
the leaf surfaces. These bacteria then fight the pathogen by producing
and releasing a class of compounds known as "iturins". These, you
could say, are directly effective against pathogens. They are the basis,
at least in part, of the original expansive claims of effectiveness. But
note - they first have to be produced by the bacteria.


The second MOA exists with respect to stimulation or induction
of the plant's own ability to resist pathogenic activity. Research
beginning in the 1990s indicated that such an ability does actually
exist and that it is translocatable. The journal Plantae* says it better
than I can:


"
Plants have the ability to increase disease resistance in distant,
systemic leaves after a local pathogen infection. This phenomenon
is called systemic acquired resistance (SAR), which is a long-lasting
and broad-spectrum resistance. Furthermore, SAR is a conserved
trait in various plant species and is important for agricultural practice.
Some mobile metabolites need to move from infected leaves to
distant leaves to establish SAR."
*

*https://plantae.org/a-positive-regul...ed-resistance/


So,with respect to "What fungal problems are you concerned about?, it
remains a valid question but when considering "effectiveness" we need
to remember that we are now concerned with what happens within
the plant itself and that lots of research is still being done. What does
"wide spectrum mean"? How long does it take to occur? How long
does it last? How about control or suppression of individual
pathogens? And remaining cognizant that SAR is a property of the plant
so that we need to think less about what is in the bottle and what
effect it might have in a few minutes or half an hour before it is washed
off in the rain.

I agree it's a complex subject and expecting miracles from foliar applied biologicals is not guaranteed particularly with really aggressive pathogens. My only pathogen concerns over the years on tomato plants have been Early Blight and Septoria. Late Blight is always a threat here in New York State, mainly because of rural Potato growers to the East leaving infected tubers in the ground overwinter but I have only been hit by LB once in maybe 10 years and that was when the plague blew up here from down South that one year.
Early blight was easy to fix when I discovered scientific studies that showed plants roots inoculated with Mycorrhizal fungi developed Systemic Acquired Resistance to Early Blight. SAR is kind of cure you've got to love, easy, cheap and no spraying. Mycorrhizal fungi has worked for me for a number of years now against EB.
Septoria is a whole different kind of fungal pathogen and I have not found any biological or systemic preventative or cure in the scientific literature, and I've tried a bunch just to experiment myself with no luck.

[amideutch]

Came across this thread that my help

http://www.tomatoville.com/showthrea...n+disease+rain

Ami

[KathyDC]

In my zone, it's mostly early blight, powdery mildew (sometimes) and septoria.

[KathyDC]

Originally Posted by RayR

I agree it's a complex subject and expecting miracles from foliar applied biologicals is not guaranteed particularly with really aggressive pathogens. My only pathogen concerns over the years on tomato plants have been Early Blight and Septoria. Late Blight is always a threat here in New York State, mainly because of rural Potato growers to the East leaving infected tubers in the ground overwinter but I have only been hit by LB once in maybe 10 years and that was when the plague blew up here from down South that one year.
Early blight was easy to fix when I discovered scientific studies that showed plants roots inoculated with Mycorrhizal fungi developed Systemic Acquired Resistance to Early Blight. SAR is kind of cure you've got to love, easy, cheap and no spraying. Mycorrhizal fungi has worked for me for a number of years now against EB.
Septoria is a whole different kind of fungal pathogen and I have not found any biological or systemic preventative or cure in the scientific literature, and I've tried a bunch just to experiment myself with no luck.

Can you elaborate - what products do you use, how? Soil drench, I guess? I'm curious because early blight almost always shows up in my garden, so I'd love any pointers.

This whole thread turned into a fascinating discussion!

Once temps rose to above 90 I switched to alternating mancozeb, daconil and copper -- unfortunately a few plants are showing fungus issues as of last week despite my best efforts at keeping ahead of it, BUT, at this point in the season it's usually much worse and more plants affected. So, I have some tweaks to make on my spraying regime for next year - but I'll call this year a success so far anyway, because it's usually a lot worse by now.