Starting with tomatoes – Part 4

Bill Kerr tells us how to take the crop through to maturity.

Starting with tomatoes – Part 4
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One of your first tasks as a tomato grower is to make sure cutworms are not a threat to your transplants. Spray a suitable insecticide, such as a pyrethroid, down the rows using a knapsack sprayer, a day or two before planting. If you are in an area where curly stunt virus occurs, treat the plants with imidaclorprid before planting. This will kill off any whitefly, the vector for
the disease.

There are resistant tomato varieties, but there will still be some damage if the disease occurs – the resistent genes ensure reduced damage, not immunity. Rather inspect the plants often for any insect presence rather than spraying extensively. Most pests can be seen at a very early stage when they can be easily controlled.

To control caterpillars when young, use Bacillus thuringiensis (DiPel), which will not harm beneficial insects. You can completely control leaf miner by sparing the parasitic wasps that feed on this pest. Many other beneficial insects are a great help if you don’t use harsh crop chemicals.

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Bollworm, which can do enormous damage, is often a sporadic pest. When the conditions are right, the night-flying moths lay their eggs on the young growth. Their damage can be seen soon after hatching and they can easily be killed. However, a single caterpillar can do much damage as it eats into fruit after fruit, rendering each fruit unmarketable. Caterpillars will also eat flowers and very young fruit and can even bore into the stem.

The message is clear: inspect the crop often and thoroughly.

Prune to keep diseases away
Pruning is an individual choice and requires labour, but it will benefit your crop. Lead staked tomatoes up between two wires or twine spaced at intervals of 30cm up the poles. Spaced about 3m apart in the row. If you lead up determinate (short-growing) varieties, prune side-shoots up to the first fork of the stem and no further. This keeps leaves off the ground, where they can become diseased.

Prune tall-growing (indeterminate) varieties to one or two stems and remove all the side shoots. This opens the plant up to more air movement, lessening the risk of fungal disease. It makes it easier to spray more effectively and you’ll use less fungicide with fewer leaves to wet. The yield will be about the same because the individual trusses become larger after pruning and the fruit is slightly larger.

Irrigation
Be careful with irrigation. If the plants suffer from lack of water, they become vulnerable to blossom end rot, where the blossom end section dies and becomes blackened. The damage will be worse if the calcium content of the soil is too low. In addition, keep the moisture content of the soil constant.

More reading
This series on tomatoes was intended as a beginner’s guide. Many books have been written on growing this crop and will provide more details.The most important rules are: don’t take short cuts, thinking this will save you money, and inspect you crop frequently – daily, if possible.