Welcome to my blog

I was born in Guernsey (but now live in Brittany) and our main industry was growing tomatoes although that industry has now virtually disappeared. Growing tomatoes to a Guernseyman is like wine to a Frenchman, it's in our blood! I do not profess to be an expert, but I have picked up a few tips and techniques which work for me.

Saturday, 15 May 2010

Tomato diseases, pests and disorders

This subject is so vast and varied, so I have added some links to the best sites that I have found. 
I will also add some of my own pictures and some from people who have sent me specific queries.

I have also added my own comments next to the links.

Sometimes, it is very difficult to diagnose a problem from just a picture, and other factors should be taken into account as some diseases look very similar to the untrained eye.

At the start of the season, most problems are caused by over or under watering, and too low a temperature. This leads to deficiencies showing in the leaves, which can sometimes look like a disease.

Organic Sprays

Ontario Crop IPM. With a great test your knowledge section.

Tomato leaf disorders.                HGIC Plant diagnostic web site

 BACTERIAL CANKER  Often confused with blight, another devastating disease, which can spread rapidly throughout your crop.

 BLIGHT (early)  Blight is probably the worst problem you could have, it is very difficult to control. Cut out all effected plant tissue and burn. Wash you hands before touching the plants again.
Early blight on tomato leaf. Leaf spots of early blight are circular, up to 1.2cm in diameter, brown, and often show a circular pattern, which distinguishes this disease from other leaf spots on tomato.

 BLIGHT (late)  I have controlled blight by spraying with a Bordeaux mix. Its is not a cure, but a good prevention measure.

 BLOSSOM END ROT   Usually brought on by underwateing.


This fluffy mould affects most soft fruit and is more prevalent during wet summers. Remove any plant material that is affected and ensure that the plants are sprayed with a fungicide as a precaution.


This disease is extremely common on most seedlings and causes the small plants to rot off at soil level. It is usually caused by a combination of any, or all, of the following reasons - crowding of seedlings, over watering, lack of air circulation, dirty containers and contaminated soil or contaminated water. Always sow seeds thinly in fresh sterilised compost in clean pots. Water sparingly with fresh tap water, and ensure adequate ventilation.

FROST DAMAGE at worse could kill your plants, but sometimes you get away with damage to the tenderest leaves. Unfortunatly, this is usually the head of the plant and if it has not been burnt too badly and  does not die, you can hopefully continue by growing up a side shoot.
The picture here from Vegetable Heaven blogspot shows  frost damage on a tomato in the greenhouse. The plants were all covered with fleece,  you can still see the bubble wrap that surrounded them. Two nights of -4 was a shock in May, but I am sure that this plant will recover, especially with the tender care that this particular person shows towards her plants.


The plants wither in hot weather and pick up at night. Leaves turn yellow and brown streaks run through the stems. Spray the plants and soil with a fungicide and mulch around the stems so that new roots can form. Avoid growing tomatoes in the same soil for at least 2 years.

LEAF ROLL/CURL There are a number of reasons why this occurs and I will try to outline most of them.
You have to take into account growing conditions, colour of the leaves, and time of year to analyse our problem correctly. Usually dark green curling leaves are not as bad as lighter ones.

Physiological Leaf Curl in Tomatoes.
When tomato plants grow vigorously in mild, spring weather, the top growth often exceeds the root development. When the first few days of warm, dry summer weather hit, the plant 'realises' it has a problem and needs to increase root development. The plant tries to reduce it's leaf area by rolling leaves. The leaves curl along the length of the leaf (leaflet) in an upward fashion. It is often accompanied by a thickening of the leaf giving it a leathery texture. Interestingly, leaf roll is worse on some varieties than others.

This is just a simple case of slight overwatering, nothing to worry about, if you just ease off on the watering a little.

This problem usually applies to tomatoes. Unlike potatoes, the curling does not indicate a disease. Inward rolling of young tomato leaves is usually taken as a good sign if the leaves are dark green. The rolling of older leaves is a sign that too much foliage has been removed from the plant or a wide variation of temperatures. The plant shown here looks like it has taken up excessive nutrients, which could be in the compost. It will settle down and should grow out of this.

 Example of unhealthy tomato leaves curling inwards, affected by contaminated manure or spray drift. Notice the very tight curly head, which is a sure sign. More Info

 Tomato (Tobacco) Mosaic Virus (TMV) Common strains cause light and dark green mottled areas on the leaves. Some strains may cause a bright yellow mottling. Plants infected in an early stage of growth are usually stunted and have a yellowish cast. Leaves become curled, reduced in size, and malformed. The foliage may have a prominent upward leaf roll. Infected fruit may show browning, internally and/or within the wall.


Magnesium is one of the major constituents of chlorophyll. Signs are a paling of the leaf between the veins, which eventually turn brown and die. It most often occurs in very acid or very limey soils. Check pH and rectify. An application of Epsom salts applied at the rate of 2oz per gallon of water and sprayed on the foliage at fortnightly intervals will also help.

This causes yellow speckles on the leaves, which may tend to turn up. Very sandy and very alkaline soils may be deficient in Manganese. In severe cases apply a foliar feed of Manganese Sulphate at the rate of 2oz per 5 gallons of water.

 RED SPIDER MITE These are normally only a problem in dry times. The mites are not visible (they are too small), but the leaves become mottled and yellowing. The solution is to spray the plants with a fine mist of water as often as possible - red spider mites hate moist conditions.

SCORCH can be caused by the sun on wet leaves, but I do find in the early part of the season that it is usually a root problem, and the plant cannot get enough water on hot days.

WATERING PROBLEMS It is common for over-watered tomato plants to have lighter green foliage compared to normal. The lower leaves will start to yellow. Reduce watering if this is the case.

 WHITE FLY Glasshouse whitefly is a sap-sucking insect pest that excretes a sticky, sugary substance called honeydew on the leaves, stems and fruits of its host plants.
The best organic way to keep them at bay is to plant marigolds near them, this really works, especially in a greenhouse. Also Basil is a good deterrent.

Other friendly ways of controlling aphids include rubbing them off with your fingers, spray them off with water and the use of insecticidal soap (a potassium-salt soap available at most garden centres). Many people have success by spraying weekly with very diluted washing up liquid - about one teaspoon of Fairy Liquid to a couple of litres of water.
Aphids breathe through their skin. Spraying with diluted washing up liquid clogs up their skin and causes them to literally suffocate. Their brains are unable to detect pain according to the majority of research, so don't worry unduly about any pain this may cause!


  1. Can u help me please?
    I've found a pic of what is happening to one of my tomato plants - but unfortunately the blurb does not say that the pic is of.
    The pic is alongside the blurb about deficiencies and is of some leaves.

    Thank You

  2. Hi Jaahda
    That leaf looks like is has the symptoms stated here in the blurb.
    'Phosphorus deficiency, Stunted plant growth and delay in plant development, purple tinged coloration on leaves, and small leaves that feel fibrous. Fruit set delayed.'
    With the dark purple on the leaf. This does ofter occour on old lower leaves, which is not really a problem. All tomato feeds contain phosphorus,in a balanced form for the plant.
    Hence on the feed you have N nitrogen P phosphorous K potash.
    Trace elements are also found in feed, and an inbalance in the plant can effect the uptake of other chemicals, so it is not always a matter of adding extra od what the deficiency is.
    If you are feeding with a good tomato feed the plant should right itself, unless there is a residue of something else, or you have not been feeding.
    It depends on how old the plant it, and if ithas been over watered, which can leach out some chemicals.
    If you can put a picture on your plant on the forum, that would help me a lot more.


  3. I think that thanks for the information and insights you have so provided here.
    I think that thanks for the information and insights you have so provided here.


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