Tomatoes can be a very rewarding crop, but they require careful management. Last week, we discussed the importance of applying nitrogen correctly to achieve the right balance between fruit set and leaf growth. This week, we’ll look at the most effective ways of controlling pests and diseases.
Most viral diseases can be eliminated, or at least the damage reduced, by using tomato varieties with resistant genes for the diseases that occur in your area. Fungal and bacterial diseases require spraying. It is very important to wet all surfaces of the plant, especially both sides of each leaf, to treat the disease properly.
As the plants get older, they are more likely to become diseased. At the same time, there are more leaves at this stage, so you should be especially thorough when spraying.
Getting it wet all over
Even with staked plants, spraying is not as easy as it seems, because the leaves hang down and prevent the spray from reaching the plant behind them. It is also difficult to wet the underside of such leaves. Small operators should rather use a motorised knapsack for this.
The finer droplets and high velocity of the air stream makes spraying more effective. You should also use an attachment that allows you to direct the spray upward to penetrate the canopy. Spray a few plants, then inspect them to make sure all surfaces are wet. Adjust your sprayer if necessary before proceeding.
I have often visited farmers who think they are doing a thorough job of their spraying, and have shown me how the chemical is dripping off the leaves. I have then turned the leaves over and shown them how dry it is on the inside.
What sprays to use
A dithiocarbamate, such as Dithane M45 and Bravo, is usually used to protect the foliage from fungal diseases. Alternating with a copper-containing product will help against bacterial diseases. You can also mix the two products into one spray – discuss this with your crop protection representative.
Effective spraying is perhaps the most important consideration when growing tomatoes. If you are not equipped to do this correctly, don’t even attempt to grow the crop.
Get them before they start