onsdag den 6. februar 2013

Aquaponics 22: Damping off problem and solution

Hello all,
So, as the problem of my 'depressed' plants continues I sought help at one of the best forums for all things aquaponic (Backyard Aquaponics). And lo and behold, one of the nice chaps there might have identified the problem.
It seems that the issue is caused by something called "Damping off". This disease causes plants to look fine one day and the next they will be depressingly sad. Their stalk will wilt away and the plant will drop or fall over. Exactly what I've been experiencing.

Damping off - Aquaponic plants looking fine 

One day the plants will look great...

Damping off - Aquaponic plant in a sorry state, but look at those roots!

And the next they will have turned into the above example of a very sorry state of being.

So, searching the internet I've read a lot about this disease. It appears to be a umbrella term for the horticultural disease or condition caused by a range of fungi.

I've narrowed my type of evil attacker down to either Rhizoctonia solani or Pythium spp:

Rhizoctonia root rot (Rhizoctonia solani) is a fungal disease which causes damping-off of seedlings and foot rot of cuttings.  Infection occurs in warm to hot temperatures and moderate moisture levels.  The fungi is found in all natural soils and can survive indefinitely.  Infected plants often have slightly sunken lesions on the stem at or below the soil line.  Transfer of the fungi to the germination room or greenhouse is easily accomplished by using outdoor gardening tools inside or vice versa.  The germination room should not be used for mixing potting soils or transplanting seedlings as a general rule.
Pythium Root Rot (Pythium spp.) is similar to Rhizoctonia in that it causes damping-off of seedlings and foot rot of cuttings.  However, infection occurs in cool, wet, poorly-drained soils, and by overwatering.  Infection results in wet odorless rots.  When severe, the lower portion of the stem can become slimy and black.  Usually, the soft to slimy rotted outer portion of the root can be easily separated from the inner core.  Species of Pythium can survive for several years in soil and plant refuse. 
Source: http://tomclothier.hort.net/page13.html

Wikipedia has this on Rhizoctonia solani
"a plant pathogenic fungus with a wide host range and worldwide distribution. This plant pathogen was discovered more than 100 years ago. Rhizoctonia solani frequently exists as thread-like growth on plants or in culture, and is considered a soil-borne pathogen. Rhizoctonia solani is best known to cause various plant diseases such as collar rot, root rot, damping off and wire stem. Rhizoctonia solani attacks its host(s) when they are in their juvenile stages of development such as seeds and seedlings, which are typically found in the soil. It makes sense then this saphrophytic pathogen would live and survive in the soil, and attack the part of its hosts that reside there. The pathogen is known to cause serious plant losses by attacking primarily the roots and lower stems of plants and although it have a wide range of hosts, their main targets are herbaceous plants. Rhizoctonia Solani would be considered a basidiomycete fungus if the teleomorph stage is abundant. and is currently not known to produce any asexual (conidia) spores although it is considered to have an asexual life cycle. Occasionally, sexual spores (basidiospores) are produced on infected plants. The disease cycle of Rhizoctonia solani is important in regards to management and control of the pathogen."

 So, I've got a nasty (and rightly feared) fungus attacking my plants. And it thrives in wet, cold poorly drained climates - a perfect discription of my growbed at the moment :-(.

There seems to be a couple of solutions (even though any type of pesticide is out of the question!) that I can try:
1) Lower the Ph of the Growbed. Bacteria and fungus dislike low levels of Ph.

2) Only plant well established seedlings. This would mean setting up a heated nursery or similar, whereby the more developed plants would be less susceptible to Damping Off.

I'll give solution number 1 a try first, as it does not involve buying anything expensive. An old and well tested way of lowering the Ph is the application of chamomile tea. This has long been known to be useful against bacteria attacks, which is due to its PH lowering abilities.
So, my plan of attack is to sow a new batch of plants, apply chamomile tea daily and see what happens. If I can detect an improvement (which should be easy) I'll carry on with this approach, and if not I'll try and set up a small heated nursery for the seedlings.

Anyways, sorry for the wall of text :-).

All the best,

2 kommentarer:

  1. Still growing with aquaponics? Your site seems quite informative. I have a fish tank and would like to try this.

    1. Hello HwC and welcome to the blog.
      Interesting question and Im glad you raised it because I've been meaning to write a conclusion to the whole Aquaponic experiment. The short answer is no. I've given up growing with aquaponics. the long answer involves, that yes it works but the demands on a proper lightsource killed my project and I could see that a "proper" setup would require a fishtank that I would not be happy with (i.e. no plants etc). So I've had fun proving that it could be done but have also concluded that with the amount of light hitting my widowsill in Denmark it was not a very productive system.
      Anyways, check back soon and I'll have a concluding post posted :-).
      All the best,


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