Highbush blueberry

A grey-brown, fluffy coating of mycelium on flowers, fruit, leaves and shoots, preceded by watery, rotting spots. It attacks weakened and damaged tissue and develops rapidly in humidity and cool conditions and where air circulation is poor. Common on strawberries, begonias, peonies and roses. The coating is characteristically 'mousy' — fluffy and ashy grey, and when the infected tissue is knocked a visible cloud of spores (conidia) puffs up, which is a diagnostic feature of this disease. Infection usually starts in the weakest tissues: fading petals, wounds, hail marks or pest feeding damage, as well as pollen residue settled on the petals. Small, brown, watery spots appear on the flowers and quickly engulf the whole bloom ('flower blight'); from the infected flower the fungus often grows down into the shoot, causing it to constrict and die back. On soft fruit (strawberry, raspberry, grapes, tomato) a watery, browning rot develops, covered with a thick layer of grey, fluffy felt — the berry softens and 'dissolves'. On seedlings and cuttings Botrytis causes basal stem rot and the sudden collapse of plants. In older, dying mycelium and on plant debris hard, black, irregular lumps form — sclerotia (resting bodies), by which the pathogen overwinters in the soil and in plant debris. The disease also shows up after harvest, as a rapidly advancing storage rot of fruit and vegetables.

The symptom affects acid-loving plants — hydrangea, rose, rhododendron, blueberry and others — grown on alkaline or calcareous soils. The leaf blade turns yellow while the veins remain distinctly green, producing the characteristic interveinal chlorosis. The symptoms appear first on the youngest leaves at the shoot tips, because iron is not very mobile within the plant and is not translocated into new growth. In extreme cases the leaves are almost white and their margins dry out. Crucially, the cause is usually not a lack of iron in the soil but too high a pH, which blocks its uptake by the roots. It is worth noting that not all susceptible plants are equally acid-loving — the rose prefers a slightly acidic to neutral reaction (about pH 6–7) and also develops iron chlorosis on strongly alkaline, calcareous soils, although it is not acid-loving in the way rhododendron or blueberry is. The pattern of yellowing is very regular: not only the main vein stays green but the whole fine network of veins, so that the leaf looks like green lace on a yellow-green background — this is the most reliable diagnostic feature, distinguishing interveinal chlorosis from the uniform, whole-surface yellowing typical of nitrogen deficiency. The symptoms intensify with each successive flush: older leaves at the base of the shoot may still be green or only slightly paled, and the younger the leaf, the paler it is, up to almost white, lemon-yellow tips. Under a long-lasting deficiency the margins and tips of the youngest leaves turn brown and necrotic, shoots grow more weakly and become smaller, and in blueberry the yield and fruit quality decline. Iron chlorosis is not contagious — it does not spread from plant to plant but appears simultaneously in all specimens growing on the same, overly alkaline site, which also helps to distinguish it from infectious diseases. Its severity can vary through the season: cold, wet and compacted soil, poor root aeration, excess calcium, a high bicarbonate content in the watering water, and over-fertilization with phosphorus additionally hinder iron uptake and aggravate the symptoms even when the element is not lacking in the soil.

Weevils 8-12 mm long, black or dark brown, with a short, broad snout, flightless and active at night. Their larvae are white, legless, C-shaped, with a brown head, and live in the soil. Symptoms: the adult beetles notch characteristic semicircular bites into leaf margins at night (box, rhododendron, bergenia, strawberry, houseplants), while the larvae gnaw at roots, bulbs and the base of shoots, causing the plant to wilt suddenly and die. The most common is the black vine weevil (Otiorhynchus sulcatus), more rarely the strawberry root weevil (O. ovatus) and related species. A key factor behind their numbers is parthenogenetic reproduction (virgin birth): populations consist almost exclusively of females, and a single female lays several hundred eggs into the soil without a male, so an outbreak builds up quickly. Life cycle: the beetles overwinter mainly as larvae (some as adults) in the soil; the adults emerge in late spring and early summer and for about 3-4 weeks carry out maturation feeding on the leaves before they begin to lay eggs, while the larvae feed on roots from summer through autumn and again in early spring. The larval stage is the most dangerous - the larvae chew the roots and gnaw the root collar at the base of the shoot (girdling), causing the plant to wilt suddenly despite moist soil and to lift easily out of the substrate; adult feeding (semicircular notches on leaf margins) mainly disfigures the plant and rarely kills it. Plants in containers are particularly at risk, where the limited root ball is quickly destroyed. The beetles are flightless, so they spread by walking across the substrate and - above all - with infested plants and substrate, which makes newly bought potted plants the main route of introduction.