There are self inflicted difficulties associated with growing tomatoes. For me that would be my inability to put leftover seeds in the fridge and just leave them there till next spring. I just have to keep planting them. (Hmm – seems that chocolate/fridge reflex got me into bad habits!)
Non self inflicted difficulties would be those associated with plant disease. Or can these also be prevented? The disease most relevant to my current immersion in seeds and seedlings appears to be Damping off Disease. So to distract me from further seed sowing or Malteser munching I’ve decided to research it in more depth.
This is what I found out (and yes all the talk of spores and fungi was enough to take the edge off my appetite and make me do a mental check as to the last time I had investigated the far reaches of the salad drawer).
What is Damping off ?
It’s a generic term for several different types of fungal diseases which attack and cause seeds or seedlings (not just tomatoes) to die.
The disease is found in soil and water but once spores develop they spread by air.
When does Damping off occur?
At three possible stages.
- Seed rot. Infected water in the compost enters the seed capsule and kills the seed before it is able to germinate.
- Pre emergent. The seed has sprouted but is still beneath the surface of the compost. If infected now no seedling will emerge.
- Post emergent. The seedling has emerged and maybe anything up to 5 cm tall. If infected now the seedling will collapse when the root or lower stem becomes infected and rots.
At 4 weeks plus the stems of the young plants should be tough enough for the danger of Damping off to have passed.
Where does Damping off come from?
The disease is present in soil or water. So places it’s likely to be lurking in the context of tomato growing are:
- Sowing containers i.e. seed trays, pots, even labels. I thought new containers would be fine as they’ve yet to come into contact with soil or water but I’ve now read a garden centre environment can be enough for contamination to take place. (I’m hoping this is alarmist!)
- Sowing compost. Again I bought new but have read that fresh from the bag is not the same as sterile.
- Water. Water from the mains (tepid not cold!) is fine. The risk is in collected rain water.
What triggers Damping off?
It’s a fungal disease so all the yucky conditions that spores thrive inwith an emphasis on dark, wet and humid! Lack of ventilation/air circulation is also a cause.
So in the context of tomato growing triggers would be:
- Over watering . If compost and seeds/seedlings are waterlogged, air/oxygen are unable to circulate.
- Excessive humidity in a propagator or greenhouse.
Too many seedlings in one container. Overcrowding means air doesn’t circulate round the seedlings AND that’s it’s easy for the disease to spread. - Low or poor lighting levels.
What can be done to prevent Damping off ?
Hospital standards as laid down by matron!
- Clean and disinfect containers before use and if using one, the same for the greenhouse.
- Water with clean mains water.
- Use fresh and sterile soil (tips for sterilizing soil include heating in the oven at 150c for an hour or at full blast in the microwave for 6 minutes).
- Sow seeds sparsely.
- Sow the seeds on the compost and then rather than covering with more compost, cover with matter that is less likely to retain moisture like sand or perlite (this is causing me confusion re Vermiculite which I used because it did retain moisture – but perhaps thinking of it’s odd consistency it’s virtue lies in being good at retaining moisture and allowing air to circulate).
- When seedlings are ready, thin out to allow air to circulate round the stems.
- Create a gentle breeze around (not directly at) the seedlings with an electric fan.
- Let the surface of the soil dry out between waterings.
- Water from the bottom up.
- Provide a light bright sunny location.
I’ve also read you should take preventative action by watering the compost/seeds with a soluble copper based fungicide. The two that get the most name checks are Cheshunt compound and Murphy Traditional copper fungicide. Cheshunt compound contains copper sulphate and ammonium carbonate, Murphy’s Traditional contains copper oxychloride. For knowing which I am now a tad better informed!
I also came across natural approaches to prevention. These included clove or chamomile tea used to spritz the plants, cinnamon sprinkled on the compost and garlic cloves crushed to either mix with water to spritz or as a soak for the seeds prior to sowing.
I haven’t used either the copper based or the natural solutions so would be interested to hear what you’ve tried and would recommend.
What happens if your seedlings do get Damping off ?
Cheshunt compound or Murphy traditional copper fungicide get mentions here as well in that they can be applied and used to protect the seedlings not yet affected. However for the seedlings that have the disease it would appear that they can’t be saved and so need to be removed and disposed of along with the compost. If containers are not disposable they must be disinfected.
I am keeping my fingers crossed that all this remains theory and not practice!
However my research makes me question if I should have taken preventative measures (either chemical or natural) at the start of the sowing process. When I was reading up on how to sow tomato seeds I didn’t come across many mentions of this step. It was only when I started researching Damping off itself that it cropped up as part of the process.
I was also struck by how many mentions air circulation and goodventilation got as part of the preventative process. This had come up in the advice I’d read on how to sow seeds and care for seedlings but I hadn’t quite appreciated how important it was. With plants my tendency is to consider light and water but not so much air. So understanding Damping off has helped me understand the importance of this 3rd critical element.
To get a better understanding yet, hearing your approach to prevention and your thoughts on sterilising soil, the use of fans for air circulation and on disinfecting even new containers would be great.
The one good thing about doing all of the above is that it makes defrosting the fridge seem like a walk in the park!
Photo by Chris Fleming
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I’m new here and to this sport of tomatoe growing. It’s my second year of trying this. I live in Ohio and am trying to get some early tomatoes started. I’ve had good success this year so far. I have a few plants about three foot tall and two feet across that I’ve started under lights. Most have blossoms and one has a tomatoe. However, I’ve ran into a problem that I thought was dampening off, but after reading I’m not sure. On some plants, mostly early girls ,they will do good for a couple of weeks or more then the bottom leaves will wilt and fall off then later the whole plant will wilt. I’ve tried all the suggestions, less water, watering from the bottom, plenty of light, it’s helped some, but I’ll still get a plant that will do this. I have’nt tried the air circulation yet ,but will. Also I get some plants, that the leaves will start to turn purple and then do the same wilt thing. It helps to cut off the affected leaves, but I don’t know what this is. This happens on plants called cold sets. Any help will be most appreciated and I’m placing you in my favorites. Thanks, Joe
Hello Joe
Lovely to hear from you and it’s great to hear from growers who are already seeing their first tomatoes of 2010. I’ve got a wait -probably till July/August so I’m very jealous !
But we’ve got to save your leaves first !
You are right – I don’t think it is Damping Off – that’s a fungal disease and with tomatoes happens when the seedlings are young, perhaps growing close together – hence poor air circulation – and that creates the ideal circumstances for the fungal spores to take hold in.
I also don’t think it’s water – you seem to have a watering routine in place. Although just a tip re that – regular and consistent watering is what tomatoes like. Irregular watering – either the timings or the amount – drying out and then getting drenched – upsets them !
I am going to take a guess based on what you have told me and say I think it’s a nutrient deficiency. In particular phosphous deficiency – which is related to the purple tinges on the plants and magnesium deficiency which is a problem with tomatoes ( and roses).
Magnesium deficiency shows up in the older leaves first – which is those at the bottom of the plant – which is consistent with what you are seeing in your plants. However an important sympton to look our for are the leaves turning yellow ( although the veins of the leaf stay green) . Are your’s turning yellow ?
Are you feeding your tomatoes – especially if they are in pots the nutrients in the compost will get used up and especially when the plants move onto flowering and fruiting they need nutrients – they are growing fast.
In the UK the best selling tomato food is a high potash food called Tomorite . It’s not avaliable in the US – but I have checked its active ingredients so you can see if you can find something similar.
It is 4 parts Nitrogen to 4.5 parts Phosphorus to 8 parts Potassium with added magnesium and extract of seaweed. It gets diluted in water and watered into the compost.
So that would form the basis of your regular feeding regime and then as a remedy for the magneisium defieciency I would recommend a foliar spray of Epsom Salts (magnesium sulphate) or a spray of liquid seaweed.
I know you are long way from the sea but the tomatoes would like a taste of the beach !
Anyway I hope my guesswork is helpful. I would love to know how you get on – and to say that I hope that first
tomato is the first of many !
Besides watering more regularly, I’ll try the food, although the potting soil I’m using has food and it is suppose to be timed released and last up to six months. I’ll also try the epsons salts. I’ll keep you posted on the results. Also, I have no yellow leaves.
Talk to you later, Joe
I’ve noticed little white spots on my tomatoe plants, they look like insect eggs or larve of some type. They don’t seem to be doing any harm at this point. Do you know what this is.? Thanks, Joe
I wondering if what you’re seeing is adventitious roots – they look really unattractive but are part of the plant as opposed to alien invader ! Here’s a photo from a previous post – does it match what you’re seeing?
http://tomatolover.com/things-that-go-bump/
I’ve noticed in tomato plants along white mark which looks like an insect was drawing a map on a leaf .what could be such a disease and what is the cause and what could be the treatment.thank you. otherwise am happy about your research on damping-off disease it has helped me write my paper.mathias
It would be wise for you to research the type of soil susceptible to damping-off disease and communicate to us.
Hello
Glad to have been of help with your paper.
I have looked up all my reference books with the symptoms that you describe and can’t find anything that matches.
With regards to what kind of soil – it’s more the case that the seedlings are crowded and the atmosphere humid… that a specific kind of soil; as seedlings are usually grown in compost.