Black Spots on Leaves. Cannot identify.

[carolyn137]

Originally Posted by bower

Well, whether there is or isn't a separate concern relative to the Potato Spindle Viroid, the article that seaeagle posted is perfectly clear, that the reasons for the ban in NZ is the concern for human health and the environment.
"“Given the serious effects chlorothalonil can have on human health and the environment, initiating a Red Alert is another way for us to help protect New Zealand and New Zealanders from chemicals that we have concerns about,” says Dr Freeth."

Also I don't know of a ban in Canada, the wiki said that there are high levels of it found in PEI - where potatoes are the main crop - and that some fish kills in PEI had been caused by runoff of the stuff. So the spuds I buy here are likely contaminated with the same residues.

@Carolyn, just browsing I came on this link to "Toxnet" at the NLM. This one really does cite a lot of sources, and covers about everything!
https://toxnet.nlm.nih.gov/cgi-bin/s...rm+@DOCNO+1546

Yes, I have that one already and now will try and explain.

If you look at my initial answer I used the word Daconil and said that came to mind since I had just asked Freda to get some Daconil on my tomato plants.

I did a heck of a lot of Googling last night and here's the best one which explains the life cycle of the viroid and points out that not all infections are lethal, some are mild,and that seeds saved from those fruits can also contain the viroid.

Since I have that link already on my fingers I'll link to it now

https://www.google.com/search?hl=en&...w=1706&bih=815

The important point,I think,is that almost all living entities are susceptible to diseases,although I can't speak to Elephants or crocodiles,etc,and that pathogens in order to infect have to have an attachment site for the susceptible crop,so lets go just with tomatoes now.

I repeat again,as I did in my earlier post above that Daconil has NO effect against any viroids and in doing my Googling I found there were a couple of NEW viroid diseases as well.

So yes, we already know that Daconil,aka Bravo,aka Chlorothalinol,can block sites on the upper leaf surface to help prevent tomato fungal diseases such as Early Blight and Septoria Leaf Spot.

But with regard to the two most common bacterial diseases,Bacterial Speck and Bacterial Spot,it isn't so easy to help prevent. Some have used Actinonvate and, some other products as well.

I'll now link to the results of a couple more of my viroid searches

https://www.google.com/search?q=can+...&bih=815&dpr=1

https://www.google.com/search?q=how+...&bih=815&dpr=1

Carolyn

[carolyn137]

Originally Posted by ddsack

Carolyn, you posted that Daconil was banned in some countries because of the Potato Spindle Viroid ...


What Marsha was asking, and what we need explained is the mechanism by which Daconil makes it more likely for PSV to infect the potato plants. What action(s) of Daconil make it likely to cause the viroid to successfully thrive on potatoes? Why would a chemical coating to prevent attachments of fungal spores make it more attractive to viruses?

I just did in post #46, relative to primarily tomato plants, since this is ahem, Tomatoville but maybe you didn't see it yet.

Carolyn

[ddsack]

Although there is a lot of information about PST viroids in the links you provided above, I didn't see anything that mentioned use of Daconil as increasing likelihood of viroid attack. I scanned a few of the most promising sounding papers, not the whole list.


I understand that Daconil cannot prevent viroid attack, but that in itself seems an odd reason to ban it, since that's not the use it is advertised for.

[bower]

Okay I found something that may help to explain Carolyn's cryptic remarks.
Oil sprays are used to reduce the transmission of virus/viroid diseases by aphids. These sprays lose their efficacy when combined with chlorothalonil, according to:
https://books.google.ca/books?id=8o7...viroid&f=false
Whew...

[carolyn137]

Originally Posted by ddsack

Although there is a lot of information about PST viroids in the links you provided above, I didn't see anything that mentioned use of Daconil as increasing likelihood of viroid attack. I scanned a few of the most promising sounding papers, not the whole list.


I understand that Daconil cannot prevent viroid attack, but that in itself seems an odd reason to ban it, since that's not the use it is advertised for.

Dee, it seems that I've failed somewhere here.

Maybe it would be best for someone to start a new thread just about Chlorothalinol.

When Tville first started I think I remember there was a Forum for growing organically,or maybe that was at the original Garden Web,now Houzz.

In any case such Forums never last long b/c of all the infighting.

But there is someone here at Tville who was once at idig, and that person might know what I'm talking about b/c that person was about the only sane one at idig in what was called the POF(Politics of Food) since many of the threads were about what was used on crops as to pesticides,and yes Daconil as well, that led to contamination of vegetables sold in a store,or stone crops, etc.,and so much more.

Carolyn, who doesn't think there is anything more she can contribute to the discussion, or can she? Other than making this suggestion above;(Maybe it would be best for someone to start a new thread just about Chlorothalinol).

[Johnniemar]

What am i missing here??? I thought they said they were baning it because of a threat to HUMAN health. What does a potato disease have to do with anything.

[Johnniemar]

I use daconil quite a bit, but i always wear a respirator, safety glasses, long pants and long sleeve shirt and hat and waterproof glives.

[carolyn137]

Originally Posted by bower

Okay I found something that may help to explain Carolyn's cryptic remarks.
Oil sprays are used to reduce the transmission of virus/viroid diseases by aphids. These sprays lose their efficacy when combined with chlorothalonil, according to:
https://books.google.ca/books?id=8o7...viroid&f=false
Whew...

I don't think any of you know how many links I had and I couldn't list all of them,but here
is another one I didn't link to

https://www.cabi.org/isc/datasheet/43659

Look at transmission and you'll find aphids,but not the same explanation that your link gave.

Me cryptic? Never.

Carolyn

[gorbelly]

I use copper at the full recommended strength, and I've never had problems with blossoms. I actually get very good fruit set in my garden. No complaints there.

EDITED TO ADD: Also, I don't avoid flowers when I spray. It would be super difficult to do so. The flowers get the same amount of spray as everything else. Still no problems.