black spots on my tomato leaves

[Martin G]

Hi just joined this forum I'm a prodigious poster on fishing forums.

I've recently got back into veg growing this year after years of not bothering mostly the summer crops I'm far too impatient to wait for winter stuff. I haven't done any scientific soil tests but just dug over my old patch and weeded and chucked a few hand fulls of that chicken poo fertilizer around, as far as I can tell it's not bad stuff with London clay underneath about a spades depth down. I will put more effort into fertility and soil structure in the future. My concern so far this is year my tomatoes (four different kinds raised from seed on the windowsill) have blackish and some have yellow spots on the lower leaves although they are growing away now. I assumed in my impatience I had put them out too early and what with cold wet weather since that was the problem but I'm not so sure.
I have Googled for an answer but nothing seems to fit exactly, does it sound like an incurable lurgy to you ?

[TPeers]

Yellow spots isn't good! Could be leaf mould - in which case remove the affected leaves and destroy - do NOT compost!

When you water make sure you avoid the leaves and try to keep the humidity down.

Don't over feed - you only need to start feeding after the first truss has set.

[Martin G]

Thanks for the reply TPeers, I am mostly referring to the ones I put out in the garden during that very warm spell a couple of weeks ago perhaps a bit too early so they have had quite a cool wet deluge on them in the past week/ten days even the ones in grow bags nearby are pretty wet, certainly when the sun does come out they perk up. I didn't know that about keeping the leaves dry.
Some that are in pots (Tumbling Tom) that I've been bringing in and out of indoors look fine so far.

[Lesley Jay]

Martin is there any chance of a photo? It would certainly help us identitfy what it might be.

[Martin G]

Can you tell anything from that Lesley ?

[Lesley Jay]

Martin you say some leaves have yellow marks on them and as it is between the veins I would go for magnesium deficiency. This can cause dark marks on leaves as well as yellowing.

[Martin G]

Is there anything specific I can do to treat that Lesley?

I have had a lot of bonfires over the years on more or less the the area where most of my tomato plants are now, isn't that good for potash ?

[Lesley Jay]

Yes, ash from fires is good for potash / potassium but high levels of potassium can cause magnesium deficiency in plants. The clay soil will be holding it rather than letting it get washed away with the rain.

If it is magnesium deficiency then you treat it with epsom salts mixed with water as a foliar spray every two weeks. I'm pretty sure you can buy epsom salts from the garden centre now and the dilution will be on the pack.

[TPeers]

Interesting that what ever it is is absent on the veins.....

So the problem is on the top surface of the leaves, not the bottom?

Can you rub the marks off with a finger? It doesn't look like scorching or blight - sooty mould? Could you have an aphid problem?

Are the dark patches dry or wet? Doesn't rellly look like a leaf miner but anything is possible!

Never seen that effect with magnesium deficiency - that's when the top surface between the veins turns yellow.

It looks almost like chocolate spot - but I didn't think tomatos got that..... it's a pea and bean problem.

Terry

[Lesley Jay]

Agreed Terry, I always associated magnesium deficiency with yellowing of the leaves but I have read that the leaves can also be a dark purple or brown and it is always between the veins. Martin did say that some leaves had yellow on them so I've had a look and the RHS has this photo of magnesium deficiency.

Royal Horticultural Society - Advice: Tomato Problems

I'm probably wrong though!!

[malcolmx]

i suggest this is sap from aphids it does not seem to be mag def have any flowers set and how many trusses so far

[Martin G]

I think Lesley that your link to the RHS tomato link shows a picture so exactly like my photo that it just has to be as you say magnesium deficiency I'll be out looking for the Epsom salts soon as I can.

Funny the yellow/gold spotting is on the lower leaves of the yellow Tumbling Tom in the grow bags whilst not on the ones in individual pots.

I have other tomatoes in grow bags as well, Marmande and F1 Incas that have the slight yellowing that are the same varieties as the ones with black spots in open veg plot, perhaps some grow bags need supplements as well.
They all are growing OK otherwise as far as I can tell and if they all produce I will have far too many, fortunately I do like tomatoes.

No trusses yet Malcolm.

[malcolmx]

all compost leaches nutriments to the water and air i take yellowing as the first signs of feed loss it can be too much water but usually its feed

if the marks on your leaves feel sticky then it is aphid goo if not then mag is probably correct . the goo and mag cling to or manifest themselves in or on the fleshier or higher parts of the leaf but a good feed of epsom salts and tommorite will buck them up
f1 incas are not an outdoor variety i think (check with dobies )and will need some protection ,not against late frosts but against temperature drop

i hope this is of use

[Martin G]

Originally Posted by malcolmx

all compost leaches nutriments to the water and air i take yellowing as the first signs of feed loss it can be too much water but usually its feed

if the marks on your leaves feel sticky then it is aphid goo if not then mag is probably correct . the goo and mag cling to or manifest themselves in or on the fleshier or higher parts of the leaf but a good feed of epsom salts and tommorite will buck them up
f1 incas are not an outdoor variety i think (check with dobies )and will need some protection ,not against late frosts but against temperature drop

i hope this is of use

OK thanks Malcolm I am a bit more reassured now, there are few aphids about because I can see them but not many yet.
One of my problems is I'm self employed (violin/restorer/maker since I left school.....1966 ) working at home in my workshop and overlooking the garden and it's so hard to resist going out there and pottering about.
It's bad enough having my pc in my workshop and spending my time on pike fishing forums and now here as well I'll never get anything done.....really I should be retired by now.

According to the seed packet my variety of incas is an outdoor kind (Suttons) anyway time will tell.

[malcolmx]

if you are as keen as i am on pike fishing try the carp society pike and predator festival in feb 09 we could meet up

work and gardening dont mix give up work

[Martin G]

I've become a total lure angler Malcolm and never fish for carp I'm afraid, I'll be at the PAC conference in September ...you?

Your right gardening and work don't mix I can easily imagine a life of gardening interspersed with pike fishing.

[malcolmx]

on the carp soc pike and predator weekend we only fish for pike a lot with lures and a lot on the fly mike brown instructs during the weekend lots of 20+ caught generaly i dont have time to attend these conferences but we have the pac people at our week end

[Martin G]

My tomatoes are looking pretty good now the cure seems to have worked and they are beginning to flower and I am optimistic.

[Lesley Jay]

That is brilliant Martin!!

[smithyveg]

Judging from the photo I really don't think you have anything to worry about.

Magnesium deficiency is a yellowing of the leaves as has already been said and I don't think it's a virus.

I've had similar markings on my indoor toms like that for many years and it never seems to affect the plant or the subsequent crop, and I think it could just be that they got a slight chill not long after planting, especially if they were growing outside. Alternatively, it could just be the way the plant grows as I find it tends to be more prevalent on the lower, older leaves.

As you say they appear to be growing well not so hopefully the 'problem' has been solved.

Regards
Simon


The vegetable grower