Bleach for initial seedling dip

[leeaun]

Hi all, have been trying to find a suitable fungicide as an initial dip for paph seedlings after deflasking but not sure which one will be safe enough to use. Here in the UK they have banned quite a number of fungicides including Physan 20 and an orchid grower told me some growers have used a few drops of bleach in a litre of water and just soak the seedlings in it for a minute before planting them in their compost. Will be deflasking some roths and sanderianum seedlings in a few weeks time and wondering whether I should try them out? Anyone with any experience in this respect?

Thanks!

 

[Ray]

I question why you'd treat them at all.

Coming out of flask, they are completely sterile, so you're not curing anything, and such treatments do not impart any resistance.

Find a biological probiotic, if you must treat them.

 

[Ozpaph]

use water only or Mancozeb. The bleach idea doesnt sound good to me.

 

[SlipperFan]

I've rinsed seedlings that show a little mold coming out of flask with a little H2O2 in some water. Seemed to work OK.

 

[myxodex]

I question why you'd treat them at all.

Coming out of flask, they are completely sterile, so you're not curing anything, and such treatments do not impart any resistance.

Find a biological probiotic, if you must treat them.

I totally agree with this.

The seedlings will have to endure some stress anyway, and bleach will just add to this.

Seedlings that survive deflasking have probably gained some induced systemic resistance (ISR), and until they do so they will be much more vulnerable to pathogens. That is probably one of the reasons why Inocucor (a mix of beneficial bacteria) has been successful for preventing damping off because it induces ISR while at the same time inhibiting pathogens and reducing stress by moderating ethylene production. I guess Inocucor is what Ray had in mind. Unfortunately, Inocucor isn't available in the UK. This is why I'm looking into vermicompost teas as these can have this activity for preventing damping off, but they can be variable with only some brews providing protection.

Two years ago I had a flask of P.ciliolare that got contaminated with a fungus while the seedlings were still too small to deflask so I had to deflask anyway in the hope of rescuing them as the fungus would have continued to grow and would have most likely created a toxic enviroment in the flask. Like Dot I washed the seedlings in approx 1% hydrogen peroxide to try and kill the fungus. Against my expectation all survived and grew well. I was lucky that the fungus was non-pathogenic as it probably induced some immunity while they were still in the flask.

You could try washing the seedlings (or even just some of them) in a dilute solution of chitosan (I could even send you some). Chitosan is a soluble derivative of chitin that is getting a lot of attention in various fields of biotechnology. In agriculture it is known to protect harvested fruits, preventing blemish and extending shelf life. Seeds treated with it germinate more vigorously and are more resistant to diseases. It stimulates wound healing in damaged trees and prevents infection. It apparently has anti-fungal, anti-bacterial and anti-viral properties, but it is not clear whether in field applications it is more the ISR eliciting properties that are more important and/or whether it is because it stimulates the activity of certain beneficial bacteria. Certainly there are studies with orchids that have shown that including it in replate media results in seedlings that are more vigorous and more resistant to infection after deflasking.

 

[Stone]

I used to use sterile pots, tools, fungicide dips etc etc. Now I just open up the flask a week or 2 before deflasking, Hose of the agar with the garden hose (under water) and pot them in a non sterile but clean pot.
Water them in with VCT and done. No losses.

 

[Ozpaph]

what is VCT, Mike?

 

[Stone]

what is VCT, Mike?

Vermicompost tea. It introduces all the beneficial bacteria which are antagonistic to the various pathogens. I've even tried pouring it straight into a just opened flask. No problems!

 

[Ozpaph]

Thanks.
Dont you think seaweed and 'carp' fertilizers would do the same?

 

[Ray]

Seaweed extracts, probably not, although they would likely supply some good stuff to the "young-uns." Fish wastes might, but they're primarily going to be sources of nitrogen.

Worm teas and commercial products like that from Inocucor are loaded with microbiological byproducts that act both to suppress the growth of pathogens as well as impart some resistance to them within the plants themselves.

 

[leeaun]

Thanks for the myriad of advice from everyone. I know the main advice is that if there is no problem, dont treat. It is just because this was the advice Sam gave to me when deflasking and he mentioned I should spray the seedlings with some fungicide after deflasking.

Ray, I have sent you a PM asking you about the cinnamon extract you made with water or alcohol. Have you used this extract as a preventative for newly deflasked paph seedlings before?