Marks on tom leaves - advice welcome

[StephenH]

My greenhouse tomatoes (not the outdoor ones) have rusty-coloured marks on some of the lower, older leaves - speckling and veining, not solid areas of discolouration. Otherwise, the plants seem healthy, and the fruit are starting to swell. Should I be worried? I've been spraying them with a 50-50 milk and water mix weekly as a specific against blight, on the advice of Alys Fowler in the 'Grauniad' Weekend magazine. Could it be a side-effect of that? Mind you, I've also been spraying the outdoor ones, and they're not showing the markings.

[rustylady]

I wouldn't worry about the markings on the leaves, I think it's just old age. The spraying with milk and water is a new one on me - I've never used it, and having seen what happens to milk if you leave it in the fridge for too long I'm not sure I want to.

[teakdesk]

Milk is a natural fungicide and works well for me against the spread of botrytis.

It has not stopped blight though and I doubt it will unless there are just very few blight spores - the blight we have had in recent years just overcomes milk.

Your speckling sounds like a bacterial infection (such as bacterial speck or similar) and I use milk against it but it doesn't seem to stop it. However, bacterial speck is not serious so I am just more careful with my watering and ventilation and ignore it. I do remove lower leaves if they are badly infected but try not to remove leaves above the lowest fruit if I can avoid it.

[gojiberry]

A diluted milk spray is fine to use but make sure it is skimmed milk. If you use full fat milk you get a build up of fat which will then go rancid.

Ian

[MalUK]

It might be an idea to reduce the milk to 20 or 25% of the mixture. Milk may have anti fungal qualities, but it's also a food source that can attract other diseases.

There's lots of other anti-fungal alternatives to milk, for example, bicarbonate of soda is one of the more potent options, but you have to be careful because it can damage certain types of plant leaves due to its alkaline nature. So, they normally recommend trying it on a small area of the leaf first and waiting a few days.

[StephenH]

Thanks for the advice, chaps. I might try bicarb instead of milk, as suggested.