Diseases & pests

Drought stress (water shortage)

Wassermangel

Drought stress arises when plants cannot take up enough water over a longer period, usually during persistent heat with no rain. Typical signs are wilted, drooping leaves that no longer recover during the day, along with brown, crispy leaf margins. Shallow rooters such as hydrangea and rhododendron react particularly quickly, because their roots barely reach any reserves in the deeper soil. Left untreated, leaf drop and flower drop follow, and on vegetables such as tomato and cucumber blossom end rot and small, hard fruits.

Flower-end rot

Calcium-Mangel

Flower-end rot is not a disease caused by a pathogen, but a deficiency symptom. Growing fruits lack calcium at the fruit tip. A watery spot forms there, sinks in, and becomes leather‑like brown‑black. Often there is not too little lime in the soil; rather, the plant cannot transport calcium to the fruit under drought stress or overfertilisation.

Iron deficiency chlorosis

Eisen-Mangel

In iron chlorosis, the newest leaves turn yellow while the veins stay green, a clear net pattern. Usually the soil does not lack iron, but it is unavailable to the plant at too high a pH. Blueberries and raspberries, as acid-loving plants, react especially sensitively, for example when the soil is too lime-rich or when you water with hard water.

Magnesium deficiency

Magnesium-Mangel

With magnesium deficiency, the leaf tissue between the veins lightens, while the veins remain green. Unlike iron deficiency, it begins on the older, lower leaves because the plant relocates mobile magnesium from old leaves to new growth. Tomatoes on light soils and apple trees with heavy fruit loads show this particularly in mid-summer.

Manganese deficiency

Mangan-Mangel

Manganese deficiency shows itself as a net like chlorosis: the leaf veins stay green while the areas between them fade to light green or yellow. The damage appears first on the younger and middle leaves in the upper part of the shoot and at first glance resembles iron deficiency, but differs through fine brown dots in the paled tissue. Affected above all are ericaceous plants such as blueberry, rhododendron and azalea, as well as grapevines, usually on soils with too high a pH. Where the shortage is stronger the shoot stays weak and leaves drop early.

Nitrogen deficiency

Stickstoff-Mangel

Nitrogen deficiency arises when plants cannot take up enough plant available nitrogen from the soil, usually on exhausted or sandy ground. Because nitrogen is mobile within the plant, it moves the nutrient from old leaves into young ones, so the typical damage shows first on the lower, older leaves: an even, light green to yellow discolouration while the leaf veins mostly still stay green. Affected plants grow more weakly overall, stay smaller and yield less than healthy specimens. Where the shortage is severe the problem is especially quick to spot on cabbage, courgette or squash, in the form of pale, listless foliage.

Potassium deficiency

Kalium-Mangel

You will notice potassium deficiency first on older, lower leaves: the edges turn yellow, brown and roll upward, while the veins stay green. In tomato the fruit at the stem base often remains hard and green (green collar), in potato and apple the leaves appear prematurely burnt and brittle. Because potassium is important for water balance and cell stability, affected plants wilt faster even on moist soil and react more sensitively to drought stress and frost.