Tomato

Tomato blight

What you will see

Watery brown leaves that quickly collapse and shrivel, with white growth on the undersides in humid weather; brown lesions on the stems, watery brown patches on green fruit, ripe fruit rots quickly.

The source says: it can be a very serious disease on outdoor tomatoes.

How to protect

1. Prevention

   • Grow resistant cultivars; even these are not completely immune.
   • Rotate outdoor tomatoes (ideally at least 4 years) and do not grow potatoes in that soil during that time either — they suffer from the same blight.
   • Keep the leaves of greenhouse tomatoes as dry as possible.
   • Do not reuse soil or compost from affected plants.
2. By hand when symptoms appearRemoving a few affected leaves only slows the spread. Use fruit from affected plants as soon as possible (unripe fruit e.g. for chutney). Bury the debris deeply or put it in the green-waste bin, do not compost it; disinfect plant supports before reusing them.

Glasshouse whitefly

What you will see

Sticky honeydew on leaves, black sooty mold and tiny white winged insects.

The source says: it is among the crops highly susceptible to whiteflies.

How to protect

1. Prevention

   • Inspect new plants and, if possible, quarantine them.
   • Get rid of unneeded plants from the greenhouse so the whitefly has fewer hosts.
2. By hand throughout the growing seasonYellow sticky traps are for monitoring, not a major control measure.
3. Biological early, before a heavy infestationParasitic wasps (from a biological control supplier) attack whitefly larvae; release them early, before plants are heavily infested. Parasitised larvae turn black.

Blossom end rot

What you will see

A circular patch forms at the end of the fruit (opposite the stalk), greenish-brown to black, ½–1 in, which becomes sunken. It is not a pest or a disease: calcium does not reach the fruit because of uneven water flow.

The source says: large-fruited vegetables like this one are particularly susceptible.

How to protect

1. Prevention

   • Keep the compost constantly moist. In hot weather water twice a day or more often in smaller amounts.
   • In pots and grow bags the risk is greatest: use a larger container, automatic watering or border soil.
   • From late fall to late winter, put at least 2 in of mulch on the bed so the soil holds moisture.
   • Apply liquid feed only to moist soil; feeding dry soil makes the problem worse.
   • Ventilate the greenhouse well during the day.
   • Spraying calcium on the leaves does not help and is not recommended. Soil usually contains calcium; what matters is steady watering and nutrition.
2. By hand as soon as it is foundYou cannot save an affected fruit. Remove it and focus on even watering so the problem does not recur on later fruit.

Gray mold

What you will see

Soft, rotting parts covered in a fuzzy gray coating.

The source says: gray mold is common on this plant.

How to protect

1. Prevention

   • Keep things clean: remove dead and diseased parts.
   • Ventilate polytunnels and greenhouses.
2. By hand as soon as it appearsCarefully remove affected parts into a bag (spores spread easily) and dispose of them.

Tomato fruit splitting and cracking

What you will see

Fruits crack in rings or lengthwise; the cracks can cork over and gray mold enters through them. The cause is uneven water and temperature swings, not a pathogen.

How to protect

1. Prevention

   • Water as evenly as possible, especially in containers; border soil smooths out swings in moisture.
   • In the greenhouse, regulate temperature with ventilation and shading.
   • Feed regularly with a tomato fertilizer higher in potassium.
   • From the start of ripening, feed with an emphasis on potassium and magnesium.
2. By hand at harvestPick split fruit as soon as possible to avoid losses. Late in the season, ripen them indoors in a warm, dark place and watch for gray mold in the cracks.