Tomato Problems: Blossom End Rot, Splitting, Blight and Wilt

First work out whether it spreads

Trouble on a tomato falls into two groups: disease, and disorder caused by uneven water or nutrients. A disorder stays on the plant it started on. A disease moves to the plant next door. Because that changes how urgently you need to act, it is the first thing to establish.

A black patch only on the bottom of the fruit is blossom end rot, a disorder. Fruit that splits is another disorder. Spreading ringed spots on the leaves, or a plant that wilts suddenly and never recovers, point to disease.

Blossom end rot: even out the water

Blossom end rot shows as a sunken black patch on the blossom end of the fruit, and it happens when calcium fails to reach the end of the fruit as it swells. Even in soil with plenty of calcium, dry spells or heavy feeding stop the plant taking it up, which is why the fix is nearly always about watering rather than about adding anything.

Affected fruit will not recover, so pick it off and concentrate on keeping the soil evenly moist. Skipping a feed helps as well. It very often appears on the first or second truss and then stops of its own accord, so there is no need to pull the plant.

1. Remove the affected fruit It will not size up, so pick it as soon as you see it and let the plant put that energy into the rest of the truss. Left on, it rots and invites disease.
2. Mulch to slow drying Straw or plastic at the base evens out soil moisture. Water the base in the morning when it dries.
3. Skip one nitrogen feed Heavy feeding blocks calcium uptake. If the leaves are curling inwards, miss the next application.

Splitting: a rain cover and early picking

Heavy rain while the fruit is coloring makes the inside swell faster than the skin can stretch. You will see either rings around the stem end or splits running out from it, and both come from a sudden change in water supply.

The most reliable fix is a rain cover. Clear plastic over the tops of the stakes cuts splitting dramatically. Without one, pick fruit that has started to color before heavy rain arrives and let it finish indoors.

1. Put a cover over the row Run a rail across the tops of the stakes and lay clear plastic over it like a roof. Leave the sides open so air still moves through.
2. Pick early ahead of rain Anything half colored can come off before a downpour and finish indoors in two or three days. The flavor is almost identical.
3. Use split fruit straight away Split tomatoes rot quickly, so pick and use them. Left on the plant they become an entry point for disease.

Blight: catch it on your weekly round

Blight arrives in cool, wet weather. It shows as dark green to brown patches spreading across the leaves and hard brown areas on the fruit. It moves fast, and can take a whole plant in a week. It starts low down, so in wet spells check the leaves near the base every week.

Take affected leaves off as soon as you see them and get them off the plot. Open up the base of the plant for air, and never water over the foliage. If it keeps spreading, use a fungicide approved for tomatoes where you live and follow the label.

1. Check the lower leaves weekly In wet weather look at the undersides of the leaves near the base. The first sign is a dark green water-soaked patch that turns brown within a day.
2. Remove and bag affected leaves Take spotted leaves off at the base and carry them away rather than dropping them. Wipe your pruners between plants.
3. Prevent with cover and airflow A rain cover keeps the leaves dry, and stripping the lower leaves lets air through. Do not crowd the plants.

Bacterial wilt: pull the plant out

Bacterial wilt is a soil-borne bacterium that enters through the roots. The plant wilts in the heat of the day and recovers by morning, repeats that for a few days, then dies while still green. Cut the stem and stand it in a glass of water and you will see a milky thread streaming out, which confirms it.

There is no chemical cure. Pull the plant out with its roots and dispose of it away from the plot, and do not grow tomatoes or their relatives in that spot for several years. Grafted plants on a resistant rootstock will prevent it almost entirely in future seasons.

1. Do the water test Cut the stem of a wilted plant at soil level and stand the cut end in clear water for a few minutes. A milky thread streaming from the cut means bacterial wilt.
2. Lift the whole plant Dig it out with the surrounding soil and dispose of it off the plot. Do not move that soil to another bed, and wash your tools before touching other plants.
3. Use grafted plants next year Choose plants grafted onto a resistant rootstock, avoid growing tomatoes in the same spot, and keep potatoes, peppers and aubergines out of it for several years too.

Soil-borne disease is all about prevention. Rotate, use grafted plants and improve drainage, and you avoid most of it.

Aphids and whitefly: find them early

Aphids on the growing tips and whitefly on the undersides of the leaves weaken the plant, but the real problem is that they carry virus diseases. There is no cure for a virus, so the whole strategy is to keep the insect numbers down.

While numbers are low you can squash them or wash them off with water. A yellow sticky trap hung at plant height catches the adults as they arrive. If an infestation takes hold, use an insecticide approved for tomatoes and make sure it reaches the undersides of the leaves.

1. Check leaf undersides weekly While you are doing the suckers, turn a few leaves over and look for small insects. Check the growing tips too.
2. Deal with them while numbers are low Squash them, lift them off with sticky tape, or wash them off with a jet of water. While they are still clustered on the tips it takes a couple of minutes.
3. Hang a yellow sticky trap Whitefly and aphid adults are drawn to yellow. Hang traps at plant height to cut down the numbers arriving.