Medium Tomato Problems: Blossom End Rot, Splitting, Blight and Pests

Does it spread, or is it only this plant?

Every problem on a medium tomato falls into one of two boxes and you should decide which before doing anything else. Disorders come from uneven water, feeding mistakes or heat. They stay on the plant that has them, they are your own doing, and you have days to correct them. Diseases and insects move down the row, and with late blight in particular a week of hesitation costs you every plant you have.

Medium tomatoes are hit harder than cherries by the whole disorder group, because each fruit spends two months on the plant depending on a steady water supply. They are hit slightly less hard than cherries by splitting, and about the same by everything fungal. The single most common thing you will see is blossom end rot on the first two trusses.

Blossom end rot is a watering problem

This is the defining problem of medium and large tomatoes. A dry, sunken, leathery black patch appears on the blossom end of the fruit, usually while it is still sizing up, and it does not heal. The cause is a failure to deliver calcium into a rapidly expanding fruit, and calcium only travels in moving water, so it is a watering problem in nearly every garden rather than a soil deficiency.

Remove affected fruit as soon as you see it, since it will not recover and the plant keeps spending on it. Then even out the water: mulch, water before the soil goes hard, and never let a container dry to the point where the compost pulls away from the sides. Skip the next nitrogen feed too, because lush leaf growth outcompetes fruit for calcium. Watch the truss above. A clean truss means you have fixed it.

1. Take marked fruit off immediately It will not size up and it rots on the plant, drawing in fruit flies and mold that then move to sound fruit.
2. Mulch and water on a rhythm Two inches of mulch and a soak every four or five days, not a heavy drenching after a dry fortnight. Consistency is the entire cure.
3. Skip the next nitrogen feed Excess nitrogen drives leaf growth that outcompetes the fruit for calcium. Move to a high-potassium feed instead.
4. Stop hoeing inside the canopy Cutting feeding roots close to the plant produces sudden onset across every truss. Mulch to suppress weeds rather than cultivating.

One or two affected fruit on the very first truss and nothing afterwards is normal on a medium tomato. That is a plant settling into its root system, and it corrects itself without any action from you.

Leaf spot and early blight climb from the bottom

Brown spots the size of a pencil eraser, with faint concentric rings inside them and a yellow halo around, appearing on the lowest leaves first, are early blight or one of the leaf spots. The spores live in the soil and reach the plant when rain splashes soil onto the lower foliage, so the disease always starts at the base and works upwards. It is manageable rather than fatal, but a medium tomato stripped of leaves in late summer cannot finish the fruit it is carrying, and that is a two-month investment lost.

Remove affected leaves the day you see them and carry them off the plot. Keep two inches of mulch on the soil as a splash barrier, strip the leaves below the truss you are currently picking, and never water over the top of the foliage. If it keeps climbing despite all that, a fungicide labeled for tomatoes where you live will hold it back for the rest of the season.

1. Inspect the bottom foot weekly While you do the suckers, check the lowest leaves including the undersides. Spots with rings inside them are the sign to act on.
2. Snap off and bag, never drop Take affected leaves off at the base and carry them away. Dropped on the bed they reinfect the plant from below at the next rain.
3. Keep the mulch as a splash barrier The mulch is doing two jobs at once here: evening out soil moisture and physically stopping spores reaching the leaves.

Late blight moves in days

Late blight is the one that ends a season. Gray-green, water-soaked patches appear on the leaves and turn brown and papery within a day, often with a fine white bloom on the undersides in humid weather. On the fruit it shows as hard, brown, marbled patches, and on a medium tomato those patches spread across a fruit you have waited two months for. It arrives in cool, wet, still spells and can take a healthy plant to dead in under a week.

There is no cure once it is into the stems. Catch it on a few leaves and you can remove them, bag them, and open up the canopy. Once brown lesions appear on the main stem the plant is finished: pull it whole and take it off the plot to protect its neighbors. Pick and use any sound fruit at once, because blighted fruit rots in storage and will not ripen indoors. Do not compost the plants and do not grow tomatoes or potatoes in that ground next season.

1. Inspect daily in cool, wet, still weather Those are the conditions the disease needs. Through a dry summer you may never see it at all.
2. Cut out early lesions the same day Remove the affected leaf plus the one either side of it, bag them, and wipe your blades before touching the next plant.
3. Pull any plant with stem lesions Brown patches on the main stem mean it is over. Take the plant out whole rather than trying to prune around it.
4. Use sound fruit immediately Fruit from an infected plant that looks clean should be eaten or cooked at once. It will not keep and it will not ripen indoors.

Airflow is the best defense available. Single-stem training, 20 to 30 inches (50 to 75 cm) between plants, lower leaves stripped and a roof over the row keeps the canopy dry enough that blight struggles to establish.

Catfacing, zippering and flower drop

Medium tomatoes show two cosmetic fruit faults that cherries almost never do, both set at flowering. Catfacing is the puckered, scarred, sometimes hollow blossom end that follows cold nights below 55F (13C) while the flower was forming. Zippering is a thin brown scar line running from the calyx down the fruit, left where an anther stuck to the developing skin. Neither spreads, neither affects flavor, and neither can be fixed after the fact, so cut the marks out and eat the fruit.

Flower drop is the other flowering-stage problem and it is temperature-driven at both ends. Sustained heat above 90F (32C), or nights above 75F (24C), sterilizes the pollen. Cold nights below 55F (13C) stop it releasing at all. Still, humid air stops it shaking loose. The plant will set again as soon as conditions return, so change nothing permanent: shade the row through the hottest hours, hold off nitrogen, and tap the stake sharply mid-morning to release pollen.

Hornworms, aphids and the things that find your fruit

A stem stripped of leaves overnight, with dark green-black pellets of frass on the leaves below, means hornworms. They are large green caterpillars that match the stem color so exactly that you will not see them by scanning. Find the frass and look directly upwards from it instead. One caterpillar strips a stem in two nights, and hand-picking is completely effective. Leave any covered in small white rice-like cocoons alone; those have been parasitised by wasps, have stopped feeding, and are producing more wasps for you.

Aphids cluster on growing tips and whitefly sit under the leaves. Neither kills a vigorous plant but both spread virus, so knock them off with a jet of water in the morning and hang yellow sticky traps at plant height. Birds and squirrels are a bigger nuisance at this fruit size than at cherry size, since a medium tomato is worth their effort: netting over the row from the breaker stage onwards is the only thing that reliably works, and picking at breaker rather than fully ripe takes the temptation away entirely.

1. Follow the frass upwards Dark pellets on a leaf mean a hornworm is directly above that spot. Search the stems at that height rather than the whole plant.
2. Wash aphids off the tips weekly A firm jet of water on the growing tips knocks them down while numbers are small. Do it in the morning so the plant dries out.
3. Net the row once fruit starts coloring Birds go for the first fruit to show color. Netting from the breaker stage onwards protects fruit through its most vulnerable week.
4. Clear fallen and split fruit every visit Rotting fruit under the plants brings fruit flies, slugs and mold. Pick it up whenever you harvest.

Keep a note of what appeared and when

Write down the date you first saw each problem, which plant had it and where that plant was standing. Problems on tomatoes are strongly seasonal and strongly positional: blight arrives in the same week of weather each year, blossom end rot shows on the same containers, and wilt takes out whichever plant is standing in one particular patch of ground.

Two or three seasons of those notes turn vague impressions into decisions you can act on. It is the difference between thinking you have bad luck with tomatoes and knowing that the third position in the row has killed a plant three years running, so nothing goes there next spring.

1. Record the first sighting date, not the bad one The week you first noticed a few spots is far more useful than the week the plant collapsed, because that is when you could have acted.
2. Note the position, not just the plant Soil-borne problems belong to the ground rather than the plant. Only a positional record will reveal that pattern.