Common fig

On leaves, shoots and fruit a black, soot-like coating forms that can be partly wiped off with a finger. These fungi do not infect the plant tissue – they grow on the sweet, sticky honeydew excreted by aphids, whiteflies, mealybugs, psyllids and scale insects. The coating therefore appears exactly where these pests feed, and its main harm is that it masks the leaf blade, reduces photosynthesis and disfigures the plants. The symptom is often seen on citrus, lime, maple and on houseplants and greenhouse plants. The coating may be thin and cobweb-like or thick, crusty and dull black — depending on the fungus species and the amount of honeydew; on evergreen plants it can persist through the whole winter. A key identifying feature: after the blade is wiped, healthy green tissue emerges from beneath the black layer — sooty mould leaves no spots, necrosis or pitting, because it does not penetrate the leaf. The extent of the symptom is also characteristic: the soot settles where the sticky honeydew drips, so it appears not only on leaves but also on objects beneath the plant — the pavement, garden furniture, a windowsill or car bodywork — which in itself reveals pests feeding higher up. The sooty mould fungi themselves are dark-pigmented (melanised) saprotrophs, which is why the layer is deeply black. Direct damage to the plant is usually moderate — weakening through leaf shading, loss of vigour, poorer appearance and reduced market value of fruit or ornamental plants — but a dense, long-lasting coating on many leaves genuinely limits assimilation and growth. Sooty mould is best treated as a visible signal that a colony of sap-sucking insects is developing higher up on the plant (or on a tree above it).

Tiny (0.3–0.5 mm) arachnids, hard to spot with the naked eye, feeding on the underside of leaves. Symptoms: fine, pale speckling (feeding punctures); over time the leaves turn grey, yellow and dry out. Under heavy infestation a fine webbing becomes visible. Warm, dry air favours their development — a common problem for houseplants in winter near radiators. Spider mites are not insects but mites of the family Tetranychidae — adults have 8 legs (larvae only 6). The most common in cultivation is the two-spotted spider mite (Tetranychus urticae): yellowish-green females carry two dark spots on the sides of the body, while overwintering females turn orange-red. In orchards the fruit tree red spider mite (Panonychus ulmi) is frequent, whose red eggs overwinter in clusters on the bark of the shoots. Feeding mechanism: the mites puncture the cells of the epidermis and mesophyll on the underside of the leaf and suck out their contents, and the emptied cells fill with air — hence the characteristic, silvery-grey, fine speckling visible from the upper side of the blade (resembling a mosaic discolouration). At high numbers the leaves turn brown, curl and drop prematurely, and the whole plant weakens and loses its growth. Dense webbing spun between the leaves and shoot tips appears only under an advanced attack and is a sign of the risk of the pest spreading to neighbouring plants. The development cycle is very fast in warmth and drought — at a temperature of 25–30°C a single generation can be completed in 1–2 weeks, hence the numerous generations per season and the rapid, exponential build-up of the population. Females lay spherical, transparent eggs on the underside of the leaves. Fertilised females overwinter (in bark crevices, leaf litter and plant debris) or — in the fruit tree red spider mite — the eggs on the bark. Early infestation is easy to miss; diagnosis is helped by shaking a leaf over a white sheet of paper (moving specks become visible) or examining the underside of the leaf with a magnifying glass.

Immobile, brown or yellowish shields (1-4 mm) attached to stems and the underside of leaves, especially along the veins. Easily mistaken for growths on the plant. They suck sap, causing yellowing and weakening, and excrete sticky honeydew. Common on figs, orchids and plants with tough leaves. The collective name covers two groups with different biology. Armoured scales (Diaspididae) have a hard waxy shield separate from the body, which can be prised off - beneath it emerges a tiny, legless and wingless female; they do not excrete honeydew. Soft scales (Coccidae) have a convex, cup-shaped cover fused with the body, and it is they that excrete it abundantly. Sticky honeydew - the domain of soft scales and other honeydew-producing scale insects, not of armoured scales - settles on the leaves and attracts sooty mould fungi (sooty mould, sooty blotch) as well as ants, which defend the colony against predators. The only mobile feeding stage is the crawler - a flat, tiny larva which, after hatching from beneath the mother's shield, disperses over the plant, then settles, inserts its stylet into the conducting tissues and loses the ability to move; adult females remain immobile for the rest of their lives. Males pupate and, as tiny, winged, short-lived insects, do not feed. In heated interiors the pest breeds all year round, producing several overlapping generations; outdoors usually 1-3 generations, and fertilised females or eggs hidden beneath the shield overwinter. Feeding symptoms are yellowing and premature leaf drop, dieback of shoots, stunting and weakening of the plant, and secondarily a black coating of sooty mould on leaves covered with honeydew. On fruit trees infested by San Jose scale (Comstockaspis perniciosa), reddish discolouration appears around the feeding sites, and heavily colonised branches die back. Because the shields are immobile and their colour blends into the bark and veins, an infestation is easily overlooked until honeydew appears or the plant is noticeably weakened - which is why regular inspection of the leaf undersides and shoot axils is key.

Insects covered in a white, cottony, waxy coating, gathering in leaf axils, at the base of shoots and on the underside of leaf blades. They look like tufts of cotton wool. They suck sap, weaken the plant and excrete sticky honeydew, on which black sooty mould develops. A common pest of houseplants and succulents. Adult females are oval, soft-bodied insects about 2-5 mm long, with a pinkish or grey body hidden under wax, often bearing waxy filaments along the sides and at the tip of the abdomen. Males are tiny, winged and do not feed. In most species eggs are laid in white, cottony ovisacs (cocoons), from which mobile larvae (crawlers) hatch and spread across the plant, carrying the infestation to neighbouring specimens; some mealybugs (e.g. Pseudococcus longispinus), however, are ovoviviparous and give birth to live crawlers without a distinct ovisac. In the warm, dry conditions of homes and glasshouses mealybugs develop all year round, in several overlapping generations - which is why a single treatment is rarely enough. Feeding symptoms are stunted growth, yellowing, deformation and premature leaf drop, and under heavy infestation dieback of shoots; the black sooty mould on the honeydew further reduces photosynthesis and disfigures the plant. A separate form is the root mealybug (Rhizoecus), forming white, waxy clusters on the roots and inside the root ball - the plant weakens and wilts with no visible pest on the above-ground parts. Mealybugs are often attended by ants, which eat the honeydew and protect the colonies from natural enemies.

A soft scale whose females form brown, dome-shaped, strongly convex "cups" (3–6 mm) sitting motionless on shoots, twigs and leaf bases. They suck sap, weakening the plants, and excrete abundant honeydew on which black sooty mould develops, disfiguring leaves and fruit. It feeds on fruit trees (plum, peach), grapevine, ornamental shrubs and houseplants. It belongs to the soft scales (Coccidae), not to the true armoured scales — its brown shield is the sclerotized body of the female and cannot be separated from her. In the Polish climate it usually develops one generation per year. It overwinters as an immature larva (second instar) attached to shoots and twigs, in bark crevices and near the buds. In spring the larvae resume feeding and the females grow quickly, turning into the characteristic, hardening "cups". Beneath its shield the mature female lays numerous eggs — often from several hundred to over a thousand. The crawling larvae (so-called crawlers) that hatch from them, usually at the turn of June and July, spread out onto the leaves and young shoots, where they attach and feed; before leaf fall they return to the shoots to overwinter. Symptoms of infestation are weakened growth and dieback of twigs under heavy attack, sticky, glossy honeydew on the leaves and beneath the plant, a black sooty coating that hampers photosynthesis, and numerous ants feeding on the honeydew. The larvae and females cluster in the forks of twigs, on the undersides of shoots, at the base of the leaves and along the veins and leaf stalks.