Blight Resistant Tomatoes
Monday, 2 December 2019 | SimplySeed
What is Tomato Blight?
Tomato Blight, which is also known as potato blight or late blight is a fungal disease (Phytophthora infestans) that can devastate outdoor tomato crops very quickly. The fungal organism can spread rapidly throughout the foliage and fruit of tomatoes, killing off leaves and causing tomatoes to rot on the plants. Affected leaves and stems will display brown spots or patches, which quickly spread and will very often give rise to areas of white fungal growth on the underside of leaves.
The disease is much more prevalent during long spells of warm, damp and humid weather. The fungal spores can be spread by the wind and carried up to 30 miles or more, which makes the disease difficult to avoid if conditions allow, such as a typical, long wet British summer.
How to avoid Tomato Blight
If previous crops of outdoor tomatoes have suffered due to blight then it’s not advisable to plant tomatoes in the same plot as spores can over-winter in the soil. For the same reason, it’s also not advisable to grow outdoor tomatoes on ground that has been previously used to grow potatoes. If you are planning to grow a small crop of tomatoes then containers or growbags might be a safer option.
Otherwise a warm, dry and sunny position is best suited rather than partial shade. Water plants at the base only and avoid planting tomatoes too close together. As a precaution water in the morning rather than leaving plants wet throughout night. Also, be vigilant. Remove any leaves that show signs of yellowing or brown patches immediately and burn if possible. Tomatoes grown under glass or in polytunnels are less likely to become infected.
Controlling Tomato Blight
It’s always best to try and avoid creating conditions, for which Tomato Blight will thrive rather than try to deal with the problem afterwards. For example, don’t feed tomato plants with fertilisers that are high in Nitrogen content. This will encourage more leaf growth and therefore produce more surface areas for infection. Also, a very leafy plant can affect adequate air circulation.
However, if plants do begin to show signs of blight infection then remove infected leaves immediately and incinerate if possible. The application of an organic fungicide can help in the early stages of infection but will offer little protection once the fungus has gained a hold. It is highly recommended that you do not plant tomatoes in soil that has previously been host to infected plants, no matter how minor the degree of infection. Ensure planted areas are kept weed free at all times.
Tomato Blight resistant seeds
Over recent years much work has been carried out in an effort to produce blight resistant tomato seeds. However, in some severe cases of infection, even plants grown from resistant seeds can partly succumb to the disease but are able to carry on growing and produce healthy fruits. Blight resistant seed has been genetically modified to ensure the plants can fight infection, whereas some tomato varieties are simply listed as blight tolerant, which is not the same. When you consider that Tomato Blight can totally destroy an outdoor crop of plants within a week then the need for a blight resistant strain has become a necessity.
These specific strains are best known as F1 hybrids, where the resulting plants will be the first generation, which have been bred from 2 different parent plants with desirable characteristics. F1 hybrids are generally quite vigorous growers and despite their hybrid qualities, there is no compromise on yield or taste.
Advantages of Tomato Blight resistant seeds
The main advantages of growing tomatoes from blight resistant seeds is you are able to grow plants outdoors in damp conditions and throughout wet summers, which seems to have become a normal feature of the British weather. Blight resistant seeds also allows you to grow and plant in areas of the garden or allotment that have previously been infected by the fungus.
For those who are unwilling to use chemical sprays on tomato plants, blight resistant seed is the obvious choice. However, it should be remembered that these specially produced F1 hybrid seeds offer a strong resistance to blight and not total immunity. The Tomato Blight fungus, like any other organism has the ability to mutate and spread at any time, if conditions allow.
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