Author Topic: Dothistroma & blight  (Read 21354 times)

Kent2106

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Dothistroma & blight
« on: March 29, 2017, 04:36 AM »
Hi All,

this is a theoretical question... 

We are into Autumn and needles start getting brown tips and dark green bands - very sure it is blight.  Pretty much all needles except the current year ones are affected. 
I believe that the fungus fruits in autumn which then releases its spores in spring - the time spraying is most effective.

Here is the question: Can/Should I pluck all diseased needles before the fungus starts to fruit (we are in autumn now) - this would then decrease the likelihood of contamination the current years growth !?
Problem is that when plucking all affected needles, the trees would be left with this years needles/growth only.

The trees are of medium vigor.

 

bwaynef

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Re: Dothistroma & blight
« Reply #1 on: April 14, 2017, 08:35 AM »
I look at this from two viewpoints.  You need to verify what it is you're up against.  In the US, there are (Agricultural) extension offices that can test for various diseases and ailments.  Do you have something like that available to you?  The next best situation would be if you have a reputable nursery close by that may have experience with what you're dealing with.

If you can't verify as mentioned above, and your belief is that you can (effectively?) manage it by spraying in the spring, why put the tree through the stress of removing needles unnecessarily?
 

Kent2106

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Re: Dothistroma & blight
« Reply #2 on: April 20, 2017, 05:10 AM »
Bwaynef, thank you for your reply!

I am pretty sure it is one of the blights -  Dothistroma has caused many problems with commercial pine growers here in SA and it is listed as the main culprit (along with cast) causing trees to suffer/die.  They don't really spray or treat in commercial growing because of high cost.  They rather chop the trees and let the ground/soil recover by not planting for a few years. But copper fungicides is what they list as treatment.

Not touching needles and start spraying in spring...this is what I have done last year! Didn't touch the tress but had a rigorous spraying program in place starting in winter  (lime sulphur, Chlorothalonil, copper fungicides) all the way through to autumn... no success. 

My thinking was to rather stress the trees now (autumn) and to eliminate fruiting bodies infecting current year needles.  Have the winter dormancy for recovering and (hopefully) no or very little spores in spring... in theory!!!

I did read on a well respected bonsai website that blight/Dothistroma can NOT be cured but rather managed by removing infected needles as soon these show signs of infection - hence reducing the likelihood for the pathogens to spread.  BUT if once infected you will not be able to get rid of it.  Can anyone confirm this???

For now my plan is to use higher concentrations of the copper fungicides and spray in shorter intervals. 
Well, I guess this is the only choice I have...
 

0soyoung

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Re: Dothistroma & blight
« Reply #3 on: May 05, 2017, 06:43 PM »
My view is that you should remove all the older needles, even ones that seem unaffected, keeping only the needles from this season's growth. Pine needle fungi are inside the affected needles - that is why there are visible effects. Keeping them only invites the formation of fruiting bodies and the release of spores to infect anything nearby. The objective of spraying is to kill the spores, IMHO.

I have been fortunate to have never had a serious needle blight type of issue. However, I spray a peroxide solution anytime I see anything I suspect to be a fungal issue on any of my trees. I prefer to leave Daconyl and the like as the nuclear options. Consider trying 2 tablespoons of 3% hyrdrogen peroxide in a quart of water. It is an effective broad-spectrum fungicide as well as anti-bacterial AND is very eco-friendly (H2O2 --> O + H2O; the reactive oxygen does all the work) ... periodic spraying at fruiting times.
« Last Edit: May 05, 2017, 06:46 PM by 0soyoung »
 
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