Know Your Enemy - A closer look at Whiteflies

Whiteflies are moth-like insects belonging to the family Aleyrodidae . Whiteflies are not true flies but belong to the order Hemiptera (true bugs ). Together [...] cabbage, potato and citrus. Life Cycle Adult females live up to six weeks, and can produce up to 200 eggs, usually laying them on new plant growth on the [...] is also referred to as a 'pupa.' Whitefly species are most easily distinguished at the pupal stage. The adult whitefly emerges from the hardened cuticle

Early blight

blight From the primary infection of leaves, Alternaria solani can spread to the flowers (especially dangerous in crops for seed production) and to the crown [...] specific symptoms. Damage symptoms Alternaria solani causes small green to dark brown spots to occur on leaves. Those spots then turn into dark brown angular lesions [...] crown. Sporulation of Alternaria occurs at temperatures from 2-4 °C up to 28-30 °C (optimum temperatures lie between 15 and 28 °C) and at a relative humidity

Damping-off

easy stripping of the skin from the root cortex with a finger nail. Life cycle and appearance of Damping-off Pythium belongs to the Oomycetes, a separate [...] which are resistant to unfavourable conditions, especially dehydration. Germination of the oospores is stimulated by exudates from roots of a susceptible [...] so-called sporangia from which subsequently zoospores are produced. Zoospores are spores with flagellae, which enable the spores to move through water.

Bacterial wilt, brown rot

potato, it is tuber-borne. Spread from plant to plant results from bacteria moving from the roots of infected plants to neighbouring plants. The bacteria [...] and when the stem is cut, bacterial slime oozes from the wound. This is the way to distinguish it from Verticillium or Fusarium wilts. Life cycle and [...] vascular browning is common with bacterial slime oozing from the cut. When the bacteria transfers to young plants through infected tubers, the wilting and

Broad mite

emus latus) are not a serious problem, as they are unable to overwinter. Mites belonging to the family of tarsonemids ( Tarsonemidae ) display a greater [...] mainly concentrated on the underside near the leaf stalk, which tends to cause the leaf to turn brown and curl up. A typical indication of an attack of broad [...] of legs in both males and females is different to the others and not used for walking. After moulting to the third larval stage the larvae stay in their

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Downy mildew of rose

nutrients from the living plant cells. The pathogens continue to grow inside the leaves and after a while new spore-bearing structures are protruding from the [...] sporulation of the pathogens extruding from the stomata. In lettuce, the foot is infected first and this causes the plant to fall over. In cabbage the stem is [...] fruits die and shrivel. Later infections cause the berries to split and one or both parts to possibly shrivel. Life cycle and appearance of Downy mildew

Phytophthora blight

enable them to move through water. Infection is usually from the root to the foot, but direct infection of the foot also occurs. Exudates leaking from growing [...] required. Dispersal is by wind and rain causes the pathogen to be returned to the soil from infected plants. Dispersal in the soil happens via water, since [...] (thick-walled mycelium cells which are resistant to desiccation) or mycelium. Zoospores are formed from the overwintering structures which infect the host

Plant health

Bacterial soft rot, bacterial stem rot

lesions first are small and sunken, water-soaked and light to dark brown. They are adjacent to wounds and natural openings at the stem end. Later the fruit [...] has also been found in the gut of insects, possibly spreading from decaying vegetation to the growing crop that way. Erwinia carotovora subsp. carotovora [...] healthy green leaves, but can grow in senescent leaves and from there grow through the petiole to the main stem through the xylem vessels. High humidity is