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Tomatoes are mostly trouble free if given proper care and attention.
Listed below are various problems that may occur.
Note; The are listed in alphabetical order rather than seriousness.
Blight;
Tomatoes are related to the potato both being members of the solanaceae group of plants, and as such are vulnerable to similar pests & diseases.
Potato blight is the main fungal disease of tomatoes and is caused by spores that are dispersed by the wind in wet conditions, and should be sprayed with an approved fungicide before symptoms occur.
The infection is seen as brown, rapidly spreading lesions on leaves and stems, and patches of rot on the fruit.
Crops grown under cover are less prone to the disease but as a preventative measure they should be sprayed with an
suitable fungicide at the same time as 'outdoor' cultivars are being sprayed.
Note; Spraying will not prevent infection, but may slow it and save the crop
Blossom end rot;
Blossom end rot is caused by lack of, or irregular watering, and appears as a brown spot at the base of the fruit, this develops into a hard, sunken ring, caused by insufficient calcium flow.
The problem generally occurs at the early part of the season when the plants are rapidly producing fruit and there moisture and calcium needs are at their highest.
Plants may need watering both morning and evening to prevent this becoming a problem.
Avoid high temperatures as this will increase the plant's transpiration rate
If plants are allowed to dry out, this will inhibit root function, which in turn impairs nutrient uptake, therefore plants in containers and grow bags are especially prone.
Over-application of high-potassium tomato fertiliser inhibits calcium uptake thus contributing to the problem.
Foliar feeds of calcium will not help and can scorch foliage.
Cracking and splitting;
Splitting of the skin of a tomato is caused by a sudden burst in growth due to fluctuating temperature or moisture levels.
Avoid this by watering regularly and ventilating adequately.
Splitting of the skin of a tomato is caused by a sudden burst in growth due to fluctuating temperature and or moisture levels.
Avoid this by watering regularly and ventilating adequately.
Plants grown in containers or growbags may need more frequent watering.
Flowering problems;
Wrong treatment can result in lack of flowers for example; it is normal practice to remove sideshoots from 'indeterminate' (vines) to form a cordon, to do so from 'determinate' plants (bushes) would result in no flowers.
Failure of flowers to pollinate, or dry set, can be due to a lack of humidity in a greenhouse/tunnel, causing pollen to desiccate before it has a chance to fertilise the flower, or excessively high temperatures e.g. above 38°C (100°F).
Conversely; low temperatures below 10°C (50° F) may result in poor pollination, this is more probable with outdoor culture.
Damping down greenhouse / tunnel floors should produce enough air movement to fertilise the flowers and reduce high temperatures.
Leaving greenhouse /tunnel doors open in warm weather will allow pollinating insects to enter, and the movement of plants by air currents should be enough to ensure fertilisation.
Prior to planting out; avoid plants becoming overcrowded in storage trays, always allow plenty of space between plants, locate them where they get maximum light, ensure that they are regulary watered (but not over watered), and fedat all times.
Leaf problems;
The most common leaf problem is; magnesium deficiency seen as yellowing between the leaf veins, and is often more noticeable on the lower leaves.
It is most likely to occur in tomatoes grown on sandy or acid soils, or where high-potassium feeds have been over-applied.
In severe cases premature defoliation can occur, but mild cases are unlikely to affect yield or quality.
Control this problem by applying fortnightly foliar sprays of 50g Epsom salts mixed with 5litres (1gall) of water.
If the leaves become both mottled and distorted they should be removed as these may indicate viral infection.
Mottling of older leaves is often due to nutritional factors and is not a cause for concern.
Leaf curl;
Tomato cultivars often curl up their leaves in a response to cool night temperatures.
This is perfectly natural and in itself not a problem.
However, it can be an indication that night temperatures are falling too low, and consideration to supplementary overnight heating should be considered.
On other occasion, leaves may become twisted / and distorted due to contamination by hormone-based weedkillers, such as lawn herbicides.
Avoid this situation by keeping a separate watering can for herbicide application, not spraying on windy days, and not composting the first grass clippings after lawn herbicide application (if using your own compost).
Tomato ripening;
Ripening depends on sufficient light and warmth: slow ripening at the end of summer might be helped by reducing shading.
Gradually de-leafing tomatoes growing under glass will improve the amount of sunlight and air getting to the fruits.
Greenback - distinct green, hard areas on the fruit shoulder, visible before ripening.
This is usually as a result of heat and/or insufficient potassium.
Choosing greenback resistant cultivars along with good ventilation, shading, and regular use of tomato fertilisers will help to avoid this.Blotches & Whitewall; this is where the skin of ripened fruit develops irregular yellow patches, with hard, white patches inside.
Avoiding overuse of nitrogen fertiliser will help prevent these.
Temperature related disorders;
Outdoor tomatoes are subject to holes and scab like scars, this is due to fluctuating temperatures during flower set, and tends to occur early in the season.
Tomatoes need warmth and will not thrive at temperatures below 12°C (55° F) hence the reason for most tomatoes in the UK being grown under cover.
Placing horticultural fleece over the plants in the early part of the season may hewlp to alleviate this problem.
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