Tomato Growing Problems And How To Control Them

P1020256Tomatoes are one of my favourite foods to grow (just in case you didn’t know!) and I really look forward to the taste of my home-grown tomatoes after waiting patiently for months on end and giving them all the care and attention that they need!

Unfortunately if you dont look after your tomato plants, you are going to get all sorts of pests and diseases which could destroy all your hard work. However, there will be times when, despite you giving your tomato plants all the care and attention that they need, the weather and other environmental stresses which are out of your control, can affect the health of your plants.

There are many types of problems that may affect your tomatoes, BUT…….we can, by taking a few precautionary measures avoid them and hopefully make your growing experience of this delicious fruit a great success.

Here are some of the most common tomato problems; I hope that this will help you to diagnose what the culprit is and treat it as early as possible to prevent it from spreading to other plants.


Botrytis or Grey mould (Botrytis cinerea) can be a serious problem when you get it in on your poly tunnel or greenhouse tomato plants. Grey mould thrives under cool, wet conditions (high humidity) and often establishes itself on dead or dying plants, including the leaves, flowers, stems and unfortunately the tomatoes.  It usually attacks unhealthy (stressed) plants but it can also infect perfectly healthy specimens too.  Tomatoes which are grown too close together (overcrowded)  will also be more susceptible – GUILTY 😦

The first symptom of Botrytis is a fuzzy grey mould which can often be missed (as I did this year 😦 ) and if not spotted early  can very quickly spread to other tomato plants as well as a variety of other fruit, veg and flowers, such as strawberries, beans, cucumbers, courgettes, lettuce, ,marigolds, aubergines, blackberries, raspberries, gooseberries and many more –  too many to name.  This grey mould is made up of dry spores that are air-borne.  These spores are dispersed very easily by the wind, garden tools, particularly your pruning shears, scissors etc.  If one part of the plant is infected, ie: if a flower that is infected drops off onto a leaf, then the leaf will become infected. If a fruit that is infected touches another part of the plant, then that will become infected too –  In other words it is very very contagious and once it gets hold it is very hard to control.

Botrytis can survive/overwinter in the soil and plant debris so it is really important to NOT use the same area the following year, this is important for all garden vegetables and is called crop rotation.   It is also important to dispose of all infected debris and fruits carefully and  DO NOT put them into your compost heap.


First things first.  The MOST important thing and number one on the list is to make sure that your greenhouse/glasshouse, poly tunnel is kept clean and thoroughly disinfect it every year, moreoften if possible.

As Botrytis is caused by cool, wet conditions and high humidity, you should avoid planting your tomatoes too close together (GUILTY 😦 ).  Remove lower leaves as soon as the plant is large enough.  Avoid watering in the evenings and try not to wet the leaves, especially on cool, wet days where there is very little wind to dry them.


What was a healthy plum tomato has been infected by Botrytiis and will rot and drop off the plant.

 If you find a plant that is badly infected with botrytis, remove it and destroy it carefully.  If you find a leave, flower or fruit which is infected, then you need to remove it by cutting it away from the main plant with a scissors or pruning shears, making sure that you disinfect your tools in between each plant treatment. I use a mild bleach solution for this.  I also use a damp cloth to hold around the infected piece so as to help stop the spores from dispersing into the air and infecting surrounding plants.

This is a leaf of a healthy tomato plant with the infected Botrytis flower buds lying on top after falling from an infected part of the plant
This is a leaf of a healthy tomato plant with the infected Botrytis flower buds lying on top after falling from an infected part of the plant
This is the infected flower buds after lying on a healthy leaf for a day or two which is now also infected :(
This is the infected flower buds after lying on a healthy leaf for a day or two which is now also infected 😦
This is a tomato and stem that are both very badly infected with the Botrytis (Grey Mould) Unfortunately I didnt see the tomato until it had infected the stem as well as other parts of what was a healthy plant :(
This is a tomato and stem that are both very badly infected with the Botrytis (Grey Mould) Unfortunately I didnt see the tomato until it had infected the stem as well as other parts of what was a healthy plant 😦


I use an organic mix of baking soda, horticultural oil, ( such as neem oil) and water to try and prevent further infection.  Spray all plants  that look like they have or are likely to have been infected by being in close proximity to Botrytis.  I also use it on areas that I have pruned.  The baking soda is known to help prevent diseases.  It also kills existing fungal spores on plant leaves.  The oil is used to help the spray stick to the plants.

This is my 1st year of trying this organic mix so I will let you know how it goes!



When you see an ugly dark patch on the bottom of your tomato it is usually a sign of Blossom end rot which is caused by a calcium deficiency in the developing fruits. Don’t panic, it really doesn’t mean that all your hard work is for nothing and that with a few minor adjustments, you can hopefully have a great crop of tomatoes.

So what is this Blossom End Rot.  Well it is caused by a lack of calcium in the developing fruits, this causes the cells to collapse in the area where the fruit has the most growth – the Blossom End (named because this is the end where the flower was, just in case you were wondering 🙂  ) and this starts to rot.  Tomatoes need large amounts of calcium for healthy cell growth and when this is not available it can put the plant, especially the fruits under stress as  fruits are the last to receive adequate calcium, hence this is why it is the affected part!

Blossom End Rot :(
Blossom End Rot 😦


Blossom End Rot is usually caused by the plant being under water stress.  This occurs when the plants soil is allowed to dry out and is then watered.  Even if calcium is present in the soil it will not move through the plant properly unless adequate watering is applied.  Too much or too little water will put the tomato plant under stress and the leaves will receive the water and calcium before the fruit which is where the problem begins 😦    Always remember that over watering can be equally as bad as under watering.

Another cause of Blossom End Rot is over-fertilization.  This is due to using the wrong fertilizer where the nitrogen content is too high.  This will stimulate lots of green foliage for your plant, but will take away the important nutrients including calcium which is needed for developing fruits  This is another reason for always using a good organic tomato fertilizer which has the correct amount of nitrogen for growing healthy plants.



Over watering after the soil has dried out can often cause split fruit
Over watering after the soil has dried out can often cause split fruit

This is something that I get on a regular basis, every year I have some lovely ripe tomatoes that split.  WHY you ask.  Well its usually because of fluctuations in the amount of water they get.  This is harder when you are growing outside as you cannot control the amount of water that nature throws at them, but it does happen under cover as well.  When a tomato gets a ‘glut’ of water in one go, it swells so fast that the outer skin (usually ripe) cracks.  The main reason is that the outer skin becomes more fragile as the fruit begins to ripen.

The best….and only way to solve this problem is water regularly and pick fruits that are ripe rather than leave them on the vine, as just one more day can cause the fruit to crack.



Some of my tomatoes infected by blight a couple of years ago!
Some of my tomatoes infected by blight a couple of years ago!

Tomato blight is another nasty disease that affects tomatoes, along with many other plants and can be disastrous if it gets hold.  Once again, dont panic as there are things we can do to prevent it and also treat it if it does show its ugly head.

Blight is most common in tomatoes and potatoes and is usually caused by very wet weather, cool nights and warm days.  It is a fungus which spreads really fast over the whole plant including the fruits or tubers, thus causing them to decay.  This is a common problem in tomatoes grown outside as you cannot control the amount of water the plant is getting, it does however also affect tomatoes grown under cover, especially when there is long periods of damp, wet conditions enveloping the outside of the poly tunnel.


Blight usually starts on the leaves of the plants but can very quickly effect the growing fruits which will quickly turn into a blackish brown hard rough surface.


Leaf of a tomato which has blight
Leaf of a tomato which has blight

Similar to Botrytis, Blight can remain in the soil for a very long period of time.  For this reason I always rotate the crop and never plant my tomatoes in the same place more than once every couple of years.  Always remove any leaves that look suspicious, ie: any that are yellow, have dark brown spots or even a fungus (spores). Remove all fruits and leaves that are infected and also any fallen leaves that may be lying on the soil as these will only prolong and spread the disease further.

Water only at the base of the plant and avoid splashing water which will only spread the spores.  Water in the morning, never in the evening as the wet cool conditions are ideal for blight to grow.

Use Bordeaux mixture which is a copper based spray and is perfectly OK to use if your an organic gardener.  It is used to protect healthy plants but once blight is present it will not cure them.  It is only used as a preventative measure rather than a cure!!

Alternatively you could try a baking soda spray similar to the one I used for Botrytis.

I do hope that this information will help you to recognize the symptoms of some of the nasty problems that can occur.   I have over the years, had all of these problems, sometimes all of them together.  With some diligent hard work I have managed to control them and still get great yields.  This year its Botrytis and it really has taken hold 😦 I do blame myself for overcrowding the tomato tunnel.  I have probably provoked the situation by not being able to open one of the doors for a couple of months.  This has restricted the air flow on top of some really damp wet days and therefore the leaves on the tomato plants remained wet longer than they should have.

Please feel free to ask questions which I hope to answer for you and please watch the video which shows you the Botrytis in a little more detail.

Please don’t forget to subscribe to my you tube channel by clicking on the link below the video.

Happy Gardening


6 thoughts on “Tomato Growing Problems And How To Control Them

  1. Your post was very interesting and informative! I have been lucky this year to have such a healthy crop of tomatoes! My deck garden has done wonderful this year producing cucumbers, several varieties of tomatoes, green beans, lettuce, and strawberries which are still blooming and giving me strawberries on a daily basis. As this was my first time using a strawberry container I think I did very and am doing very well. I will do a few things different next year such as lining up my tomato containers near the deck railing so that they can be tied to the deck railing on windy days which is important since they have grown past their tomato cages. However, it has been a great experience and one that I will continue next year!


  2. I seem to have something munching the leaves of all my tomato plants, I don’t see any insects or tomato worms, can I save the plants? I hope you can help. Thanks for your excellent blog, you have some very good information on here.


  3. I wish I had come across your post sooner. Was told that I had botrytis cinerea on my tomatoes but it could well be blight – or both! In any case, I am very sad that my plants have been so afflicted. Let’s hope for better things next year 🙂


  4. Thanks for the great info. Great to actually see the problems on video, but the sound seems very low even when I turn it up full. Looking forward to reading more from your blog, as we live in the same general area of south Ireland….Cheers from Catherine x


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