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08/07/2012 at 11:28

But he's feeding weekly with a potassium-rich feed, and he's been watering daily and magnesium is so water-soluble it could be leeching out.

Maybe we're looking at two problems?

08/07/2012 at 12:00

Hi all!

My wife and I have just had a good look at all of the plants. The main stems and all of leaf stems (up to the affected leaves) look in perfect health. Looking at the brown spots with a magnifying glass - on leaves at various stages - there are no halos or concentric rings. The spots seem to be made up of clusters of dots. On the worst affected leaves, they look almost like scabs. A few of the worst leaves are wilting, and look like they have small patches of fungus, but I think this a secondary problem - I don't think it's part of the main problem.

I have taken the following photos - in macro - I hope they will give a better view of the problem.

The last 6 photos are the back/front of three of the worst affected leaves that I removed.

Thanks to all once again.

08/07/2012 at 12:06

Sorry folks, there is obviously a limit on the no/size of picture uploads. I'll try to send the last photos again.

 Pics 3, 5 & 7 cearly show the mold I was talking about.

08/07/2012 at 13:07

Gard, I think it's probably one of the Leaf Spot diseases, and Dove might be onto something with the added deficiency problem. As I said earlier, there's nothing you can do to treat fungal problems once they're established. You can only remove foliage, trying not to remove more than about 30%.

Apart from that, I'd cut back on both the watering and feeding. To hark back to the watering situation: regular watering just means watering to a pattern and the pattern is dictated by the plant's needs. Simply, if the mix is damp, the plant doesn't need water. The trick with containers is to poke your finger as deeply into the mix as you can. The surface might appear dry, but it's the first thing to dry out, along with the outer edges of the mix. So test the mix as deeply as you can towards the middle of the container. Any dampness at all means water isn't needed. Continually watering already damp roots just means a plant with wet feet and few plants - least of all toms - prosper with wet feet. If it takes three days for the mix to dry out, regular watering, in your case, would mean every three days. And, when you water, water well. Then let the mix dry out again. And so on. I have to say I would be enormously surprised if a container that size, in that position, needed water more than every three days. Look at the example of my neighbour's plant - in a container, in 6 hours of direct sun, with the temps around 35C - not needing water more than every two days.

Cut back the feeding to once a month. Dove is right in that potassium-rich fertilisers can impact on the mix's nutrients. And the simple fact is that toms don't need that much fertiliser. As I suggested earlier, an over-watered and over-fertilised plant isn't a happy, healthy one. It's bloated and vulnerable. Less is much preferable to more in terms of both water and food.

Change the regime, give it a few weeks, and let's see how things look.

08/07/2012 at 15:45

The damaged leaves look exactly like a fungal leaf-spot disease I had many years ago, when I first got a greenhouse.  In my enthusiasm, I installed a misting system which I thought would be a good idea.  It turned out to be disasterous and I had just about every tomato disease I could look up!  The moral of the story is that tomatoes hate getting their leaves wet, which allows naturally occuring fungal spores to germinate and more easily take hold.  Once a leaf-spot type fungal infection starts, spores are produced very rapidly and in huge quantities.  These days I am extremely careful to only water tomatoes at the roots, and only when the compost surface is dry.  I've also found that watering in the morning causes fewer diseases than watering in the evening.  Contrary to some common recommendations, I never wet the greenhouse path to increase humidity - tomatoes do not need high humidity  and in my opinion it can only encourage fungal diseases. I fully agree with everything that Italiophile says about watering and feeding regimes.

08/07/2012 at 17:07

Spot on, Bob - and I use the term advisedly in light of Gard's problems - humidity is an invitation to fungal problems. As is any sort of moisture on the leaves, especially overnight. It's always best to water in the mornings.

I helped a friend just outside Cortona set up her vegie garden. She installed an overhead sprinkler system. I told her she was in for trouble. Sure enough, her tom plants - and quite a few other things - are plagued by fungal problems.

Also, fungal spores can and will drop onto the soil under a plant and can be splashed back up again when watering. I maintain a gap of about a foot to 18" between the lowest foliage and the soil to help guard against same.

08/07/2012 at 20:20
Apologies for the delay in responding, it's been a busy day.

Thank you Italophile for the latter advice, especially re the watering - at last something that is logical and makes sense.

Regarding Bob's comments. I have been careful to only water at the roots (using house tap water), avoiding the leaves and any splashing, and I don't use any form of misting. However I do have gravel trays on staging for plants that I am raising from seed / cuttings, as mentioned above. I have noticed that each morning, the inside of the greenhouse is misted up and some of the leaves on the tomatoes, cucumber and other plants do have water droplets on them.

However, if this is the cause of some form of fungal infection, then why have my outdoor tomato plants (grown from the same seeds & planted in the same potting mix etc), only yards from the greenhouse, not also been affected, especially as they have virtually been drowned on a daily basis over the past few months due to this dreadful weather?
08/07/2012 at 23:53

Hi Gard, The problem is that greenhouses don't get the same air flow around the plants that happens when they are grown outside and the air tends to circulate around the greenhouse spreading the spores much faster than would happen outside.  I've remembered the name of the disease now - Cladosporium fulvum.  The tell-tale clue is the slightly purple patches on the undersides of the leaves.  Have a look here:



09/07/2012 at 06:59

Good one, Bob. I've never had Leaf Mould problems but then I've never grown in a greenhouse. You hardly ever see it on outdoor crops.

Gard, LM is about the most common fungal problem for greenhouse toms. As Bob says, it's down to air circulation, the enclosed environs of the greenhouse effectively turning it into an incubator. You have to aim for as much ventilation as you can to keep introducing fresh air from outside. A friend of mine used an electric fan on low speed to help the process.

Rain can be one of the enemies of outdoor tom crops because of the wet foliage. Unless you spray preventively against fungal diseases+, all you can do is (a) keep a sufficient distance between plants - at least 3 feet - to help air circulation; (b) avoid letting clumps of foliage develop both on individual plants and between adjacent plants - hindering air circulation - by judiciously thinning foliage; (c) plant in a sun trap, a position that will let the sun dry the foliage as soon as possible; and (d) observe basic housekeeping practices like watering in the mornings, avoiding wetting the foliage, and maintaining a safety gap between the lowest branches and the soil.

+Even if you spray preventively you still need to observe the same fundamentals.

Unfortunately, for some reason, tomato growing seems to have been turned into a complicated process with a lot of misinformation circulating. For example, I read on a dedicated tomato website that a plant that wilts is ruined. Which is rubbish. Outdoor toms will wilt in the heat of the day. The key is to check the plant's condition after the sun goes down. If it has perked up again, no problems. If it's still drooping, it's an indicator that it's time to water. But the plant isn't ruined. This sort of misinformation is predicated on the notion that toms are delicate, sensitive plants. And they're not.

Tomato growing is a relative simple process. Observe basic cultural practices, don't pamper them, keep them alive, and let them get on with reproducing themselves.

09/07/2012 at 09:08

that is the most comprehensive and informative lesson on growing tomatos that i have ever read, thank you to all the people who contributed,   

09/07/2012 at 14:22

Hi all!

I checked out the website that Bob suggested (Cladosporium Fulvum - leaf mould). The leaves on my tomato plants, especially the recently affected ones, don't show the same signs as those of Cladosporium Fulvum. Using a magnifying glass, they only have tiny brown dots on the top of the leaves and are totally clear underneath. In fact the more advanced leaves don't show anything underneath until the dots have formed into large clusters and the tops of the leaves start yellowing.

Re the ventilation, as mentioned previously, I have two atuomated window vents, as well as a ground level louvre window, and of course the door, the latter two of which are opened fully every day, and I can see the circulation wafting the leaves of the greenhouse plants.

The greenhouse is also planted in THE sunniest part of the garden, and has a good clear area around all sides. 

I have contacted the helpline of another very large gardening organisation (I joined at GW Live), who, on being directed to the photo's on this website, stated immediately (and again, following consultation with a tomato expert) that the problem was not an infection, but is a deficiency in magnesium. They advised treating the plants with epsom salts every two weeks, until the problem clears.

A suggestion for the possible cause, was that I created my own potting mix (following an article in GW), and that the PH balance / nutrient level (and other things that I forget) is not perhaps what it should be, and in future, to use new ready made compost for any vulnerable plants like tomatoes.

I have since carried out a number of their suggestions to test for potential problems:

(1) Test the soils PH - in my case the soil test kit indicates a PH level of 6. The same kit suggests a PH range of 5.5 to 7.5 for tomatoes. I am therefore towards the acidic end of this range, but still within parameters.

(2) Check that the root growth is OK. My tomatoes are planted in purpose made plastic rings (the retail version of a large pot without a base), sited on the top of the larger growing pots. I checked the roots within the plastic rings and the larger pots. I was amazed. There is a massive, dense, healthy looking root system that goes down to at least 6" below the plastic rings (as far as I could get down into the pot), with no sign of water saturation.

Following all this advice (thank you all!), my plan of action is to follow Italophile's (a), (b) and (d) - the greenhouse is already in the sunniest spot, so not (c) - as well as his excellent watering advice, plus persevere with the epsom salts, and of course next year, not to use my own potting mix.

I will keep you up to date with the progress.

With all this talk of possible fungal infection, I forgot to ask, what do you do at the start of the season to limit the likelyhood of such an infection in the greenhouse?

Many thanks once again.

09/07/2012 at 14:36

Gard, a pH of 6 is ideal for toms. They prefer it slightly acid. A homemade mix might well explain some nutrient deficiencies, but I haven't seen those sorts of lesions before as a result of, especially, magnesium deficiency.

In terms of limiting the chances of fungal problems - if you don't want to spray, you just have to adopt all the housekeeping practices mentioned above. And, in a greenhouse, most of all, great ventilation.

You will never escape fungal spores. They're airborne, they're everywhere, and effectively invisible. All you can do is create an environment that gives them the least sympathetic conditions.


09/07/2012 at 15:24

Thank you once again Italophile.

Great news re the PH level.

I guess I'm hedging my bets with my 'plan of action', i.e. using your advice to treat a possible fungal infection (esp re ventilation), and the epsom salts for the suggested magnesium deficiency - hopefully, it can't hurt?

 Re spraying for fungal infections, what do you spray with, when, how etc, etc?

09/07/2012 at 15:49

Looked and sounded like a magnesium deficiency to me, with a secondary problem once the leaves were damaged by the deficiency - but it is very hard to tell definitively from photographs.

09/07/2012 at 15:58

No, spraying for the deficiency won't hurt. I think it's about 20g ES per litre of water. Spray in the mornings to let the foliage dry out during the day.

Spraying against fungal problems has become a tad controversial these days. Most of the common fungicides are chemicals and many are reluctant to use them and with good reason. They poison foraging insects amongst other things.

The most common organic treatment is a copper sulphate spray. Very popular here in Italy. You see tom plants everywhere with bright blue leaves. But, while it's organic, it's also a metal, it can eventually build up in the soil, and doesn't do foraging insects much good either. I don't use it because I don't like metal building up in the soil.

The very best treatment I ever came across - and used when I was back in Australia - was a chlorothalonil-based spray. It comes under various brand names - Daconil, Bravo, etc. It's synthetic, a chemical, but harmless to foraging insects. It will kill fish if you pour it into a fish pond. So I didn't pour it into any fish ponds. It's very widely used in the US - the home of heirloom tomato growing - and even by many organic growers. They acknowledge that it's not organic, but (a) it doesn't harm the garden wildlife; and (b) it's stunningly effective.

Problem is, it's hard to come by outside the States for domestic use. In fact, in Australia, it was only available in bulk for farm use. So a group of us tomato growers all chipped in, bought a container, and divided it up. It worked brilliantly.

A week or so ago someone posted in this forum about spraying with milk against fungal problems. Some people do, and swear by it, but there's no scientific evidence that it works. At best, it's thought that the milk might amend the pH of the leaf surface to a figure less sympathetic to the spores.

The principle of spraying against fungal problems isn't that you kill the spores. You can't. You spray preventively - before the spores arrive - and coat the leaves (on both sides) efectively stopping the spores getting a grip. Normally you would start spraying just after planting out and about once a week thereafter. If it rains, obviously, you have to respray. It's not always failsafe - though I found the chlorothalonil was - but it's the best you can do in terms of taking positive action.

I don't spray here in Italy but only because I can't get chlorothalonil here. I just do all the basic housework and hope for the best. I get Early Blight and Septoria Leaf Spot - the two most common fungal problems in the home garden, and they're pretty inevitable - but nipping off affected leaves as soon as the symptoms appear keeps things under control.



09/07/2012 at 22:25
Thanks once again for the advice.

I was just flicking through the June 2012 issue of 'another large gardening organisation's magazine' - (I don't know if mentioning the name of the organisation/ magazine is an infringement of some kind, so I had better not use them) and on page 2x there is a picture of a tomato leaf affected by magnesium deficiency. It is identical to the leaves on my tomato plants during one stage of this progressive problem. So thankfully, I at least know for sure what the problem is.
10/07/2012 at 06:02

It's been a fascinating couple of days, Gard. A good garden mystery is always fun - except when you're on the receiving end!

10/07/2012 at 09:26
Hi Italophile. There is still a mystery! My outdoor tomato plants (identical plants, compost, pots, watering, feeding etc, etc) don't have this problem - Why?

The article I mentioned above talks about using Epsom Salts to the soil, and later, as a foliar feed - doesn't mention if you can/should use both at the same time. Any ideas?

For soil treatment it mentions the amount of ES, but not if this is applied dry to the soil & then watered in, or applied as a liquid solution - if the latter, it doesn't mention what the mix ratio should be. Any Idea?
10/07/2012 at 09:42

That's why I think the problem has been as much disease as deficiency. Or in fact more disease than deficiency. If it were more deficiency, all the plants in the same compost should suffer the same problem.

Out of interest, could you post that recipe you used for the home-made mix?

ES is usually applied as a foliar spray. The leaves absorb the ES, a faster-acting process than going via the roots, whereby the roots first have to absorb the product before distributing it. Mix up 20g ES/litre of water and spray once a day for a week or 10 days and see how things look.

10/07/2012 at 10:10
Hi Italophile. Thank you once again for the info.

The compost mix, using a 1.5 litre pot, is in the following ratio:

2 x J. Arthur Bower's multi purpose compost.
2 x sifted garden compost (a mix of garden and food waste [potato peelings etc] fully organic - I don't use anything on the garden except on my pots - Miracle Grow, or Tomorite, used as per instructions).
2 x sifted basket compost (last years).
2 x perlite.

I also add in 2 scoops (about a teaspoon per scoop) of water retaining crystals.

I have used exactly the same mix on all of my pots & baskets (whether flowers or veg) and with the exception of the greenhouse tomatoes, I don't have a problem.

Just going out to spray the leaves.
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