Disorders usually indicate that something is wrong the growing environment, watering or nutrition of the crop.
Diseases of tomatoes
Late (potato) blight
Late blight (Phytophthora infestans) affects both tomatoes and potatoes. The disease survives over winter on volunteer potatoes (plants growing from tubers left in the ground). Spores can also blow in from nearby infected crops. In warm, wet seasons the disease spreads rapidly – it’s less of a problem in fine weather. Commercial potato growers use ‘Smith periods’ to predict when their crops are at risk (two successive days with temperatures above 10°C and relative humidity above 90% for more than 11 hours each day). You can see when these are forecast here: Blightwatch. The only materials available to gardeners for the control of blight contain copper and are ‘protectants’ which means they have to be applied before the plants are infected, with coverage of all surfaces. Copper is toxic to aquatic organisms and it accumulates in the soil so we don’t use it in our garden.
If you are in a high-risk area, choose some blight-tolerant varieties; we have selected six of the best for our Blight-tolerant Outdoor Tomato Collection.
Other leaf diseases
Many modern F1 varieties e.g. Shirley F1 are resistant to the most common leaf diseases such as Leaf Mould (Cladosporium) and Tomato Mosaic Virus (TMV) (Gardener’s Delight is NOT resistant to TMV). Powdery mildew can also be a problem in some years.
Root diseases
If you have a small greenhouse and always grow your tomatoes in the same place, then there can be a build up of soil-borne diseases such as Fusarium (wilt; crown and root rot), Verticillium wilt and Corky root rot. You can get round this either by not growing in the soil or by using grafted plants.
Pests, diseases and disorders of tomatoes
Pests, diseases and disorders of tomatoes
If you can’t find the answer to your problem here, tweet your veg gardening woes to me and I’ll advise/sympathise @AgonyPlant, or if you’re not on twitter, email agonyplant@delfland.co.uk
Pests, diseases and disorders
If you can’t find the answer to your problem here, tweet your veg gardening woes to me and I’ll advise/sympathise @AgonyPlant, or if you’re not on twitter, email agonyplant@delfland.co.uk.
There are 3 key areas:
Tomato Variety Choice
Firstly, decide what sort of tomato you want to grow. Cherry varieties get ready before larger types and have a more concentrated flavour. Large varieties such as plum and beefsteak are trickier for beginners. I recommend:
Shirley F1 AGM: very early, short-jointed variety suitable for heated or cold glass/polytunnels; heavy yields of top class fruits; resistant to TMV, Cladosporium and Fusarium.
Sungold F1 AGM: golden-orange cherry – good yield of attractive round fruit; good flavour
Sweet Million F1 AGM: red cherry – long trusses of sweet fruit; good yield
Tumbler F1: early bush variety for baskets & tubs; red cherry-sized fruits with excellent flavour
I have grown all of the above varieties outdoors in East Anglia.
Blossom-end rot
Disorders of tomatoes – page discussing disorders – Blossom-end rot
Blossom-end rot
Blossom-end rot (BER) is due to a lack of calcium in the distal end of the fruit (the end where the flower dropped off) opposite the calyx (where it is joined to the plant). Sometimes there is an internal black rot with little or no external signs. It is seldom due to an actual deficiency of calcium in the growing medium or soil. Calcium is taken up passively and carried in the ‘transpiration stream’. It can only be absorbed by actively growing root tips. All this means that there can be several underlying causes:
- erratic watering, especially in peat bags
- sudden transition to low humidity after a period of dull weather
- root damage
- surge in vegetative growth due to high Nitrogen liquid feed or fertilizer, particularly if there is a high proportion of ammonium rather than nitrate-N
- excessive fertilizer or feeding
Take off all the affected fruit (it tastes bitter). Try to maintain an even amount of moisture in the soil or growing medium. Feed with a high potash feed once the fruit start to swell, according to the instructions on the packet. If the plants are growing in a greenhouse, don’t keep the vents closed during humid weather, leave slightly open. Plum and beefsteak tomatoes are much more prone to this disorder than cherry varieties.
Diseases of tomatoes
Diseases for tomatoes
Late blight (Phytophthora infestans) affects both tomatoes and potatoes.
Diseases for tomatoes
Key diseases for tomatoes:
Planting & spacing tomatoes
Spacing
Tomatoes need about 0.4 sq m (4 square feet) per plant, so you can plant them 60cm X 60cm (2ft X 2ft) or 46cm (18 inches) between in the row and 87cm (21/2 ft) between rows.
Planting
By the time conditions are suitable for planting, you may be able to see the first truss in bud or just opening. Your plants may need a small cane to support them if they start to flop over. It is very important to remove the first truss shoot early so that you get a strong first truss. This is a side-shoot that grows in the axil below the first truss. For details of how to remove side-shoots see our helpful video on YouTube: Twisting Tomatoes – (training and side-shooting tomatoes).
Make a hole with a trowel, and plant as deep as possible without burying any of the leaves, or covering the graft union (if your plants are grafted).
Soil preparation for planting tomatoes
Soil preparation for the tomatoes
Tomatoes prefer a well-drained soil or growing medium which encourages a deep and healthy root system. Organic matter is essential to develop and maintain good soil structure – well-made garden compost is ideal.
Soil preparation
Tomatoes prefer a well-drained soil or growing medium which encourages a deep and healthy root system. Organic matter is essential to develop and maintain good soil structure – well-made garden compost is ideal. The best way to find out the nutrient status of your soil is to have it analysed – The RHS offers a soil analysis service. Tomatoes prefer a soil pH in the range 6.0 – 6.5 i.e. slightly acid, but this is a bit too low for some crops such as lettuce and brassicas, so you might need to aim at between 6.5 and 7.0. However don’t apply lime immediately before planting tomatoes unless the pH is below 6.0.
You should aim to apply all of the Phosphorus and Magnesium needed for the whole season, part of the Potassium (also known as potash) but little or no Nitrogen, or else you will get lots of lush growth and your flowers won’t ‘set’ fruit. Don’t forget that your garden compost should contain a lot of nutrients. In the absence of a soil analysis, apply a high-potash fertilizer e.g. Chase Animal-Free Tomato Fertiliser according to the recommendations on the packet; fork in the fertilizer or compost to a depth of about 20cm.
To graft or not to graft tomatoes?
To graft or not graft for tomato growing?
To graft or not graft?
My advice is that grafted plants are worthwhile if you are growing tomatoes in the same soil year after year (usually in a greenhouse). You are unlikely to see a benefit from the disease-resistant rootstock if you are growing in grow-bags or containers using fresh growing media. You may still benefit from the extra vigour resulting in an earlier first pick or an extended harvest period at the end of the season. If you buy grafted seedlings, make sure the graft is above the surface of the compost when you pot them up or plant them. If you don’t, the scion may produce adventitious roots and you will lose the benefit of the rootstock.
Grow bags and containers
If you are using grow bags make sure they are placed on a firm surface, slightly sloping away from your path. If you’re using pots or other containers, the bigger the better, not less than 12 litres per plant; fill them with a good quality peat-free growing medium recommended for containers such as Fertile Fibre Multipurpose Compost or Melcourt Sylvagrow (peat-free, but not organic), both Gardening Which Best Buys.