Tomato

Dry, sunken, tan or dark patches on the blossom end of developing peppers, often on the first fruits or during heat and drought.

Remove affected fruit and fix the watering rhythm - subsequent fruit will be clean. Calcium sprays are largely cosmetic theater.

Even, consistent watering plus mulch to buffer swings; the soil almost always has enough calcium, so delivery, not supply, is the problem.

Not a disease: a calcium-delivery failure caused by uneven soil moisture, appearing as a sunken tan-to-black leathery patch on the fruit's bottom.

Wilting, yellowing, and browning of plants (often in patches), stunting, and death, worse where flax has grown before ('flax sick' ground).

No cure for infected plants - remove them, and rotate away from flax for several years; resistant varieties and rotation are the real controls.

Grow resistant varieties; rotate away from okra (and related mallows) for several years; ensure good drainage; control root-knot nematodes, which open the door to wilt.

A soil-borne fungus (Fusarium oxysporum f. lini) that infects flax roots and clogs the water-conducting tissue, causing wilting, yellowing, stunting, and death, and persisting in the soil for years - the classic 'flax sick' soil problem.

Numerous small brown-to-tan spots, sometimes with darker margins, spreading on the foliage after wet spells.

Remove and trash affected leaves promptly; improve airflow; copper can protect new growth if pressure is high.

Space for airflow, water at the base, use disease-free seed, and rotate away from Apiaceae beds.

Fungal disease (Septoria petroselini) that spots parsley foliage with small tan-centered lesions in wet, humid weather, disfiguring the leaves.

This is the V in a VFN-resistant tomato variety, and choosing one is the simplest control there is. Verticillium is the cool-soil counterpart to fusarium wilt and produces the same vessel-clogging pattern; the V-shaped yellow lesions on the lower leaves are the tell.

One branch, one limb or one side of a plant wilting, yellowing and browning in summer while the rest carries on normally - the lopsided pattern is the tell - and leaves that wilt and then hang on rather than dropping cleanly. Cut into affected wood and look for olive-green, grey or brown streaking along the grain; in a cut vegetable stem it shows as a ring of discolored dots. On vegetables, lower leaves yellow in a wedge from the margin inward, and the plant wilts at midday but recovers overnight in the early stages.

There is no cure and nothing to spray. On a tree or shrub the aim is to keep it alive long enough to compartmentalize the fungus, which many plants manage for years: prune out dead and wilting branches well below the discolored wood, sanitize the pruners between cuts, water deeply through dry spells, mulch, and feed lightly rather than pushing it with a heavy feed. On vegetables, pull and bin affected plants rather than composting them, and move that crop to clean ground or to containers of fresh mix. Do not replant the same species where one has died.

There is no way to sterilize garden soil of it, so prevention is plant choice and plant vigor. Do not replant a susceptible species where one has already died of it. Grasses, conifers, ginkgo, hawthorn, hornbeam, honeylocust, oak and beech do not get it, and many vegetable varieties carry bred-in resistance - the V in a VFN code on the seed packet. Rotate susceptible vegetables on a long cycle and keep them off ground where the disease has shown. Buy clean stock, avoid wounding roots with spades and machinery, and keep woody plants steadily watered, mulched and only lightly fed, because a vigorous plant walls the fungus off far better than a stressed one.

A soil fungus (Verticillium dahliae and relatives) that enters through the roots and grows upward inside the water-conducting tissue, plugging it from within. The plant is not being eaten or rotted, it is being cut off from its own water supply, which is why the signature symptom is one branch or one side wilting and browning while the rest looks perfectly healthy. Cut into affected wood or stem and the tissue is streaked olive-green, grey or brown. The host range is enormous - maples, redbud, olive, tomato, potato, pepper, eggplant, strawberry and many more - and the fungus survives in soil for years as tough resting structures, so infected ground stays infected. Grasses and conifers do not get it.