White leaf spot (Ceratocystis paradoxa, Thielaviopsis paradoxa)
The fungus Ceratocystis paradoxa causes white leaf spot, black rot, base or but rot and soft rot or water blisters. White leaf spots are yellow to brown and several centimetres long. Later they dry to become papery and straw coloured.
Base or but rot of pineapple is a common disease of crowns, slips and suckers used for establishing new plantings. Rot of planting material occurs when they are not dried and are packed with little aeration. The fungus also destroys older plants by entering through wounds caused in the collar region while weeding or other field operations. In severe conditions the entire plant may turn dark and rot within 2 or 3 days.
Black rot is a post-harvest disease occurring only on injured pineapple fruit. Only freshly cut or injured tissue is infected, and a soft black rot with dark coloured mycelium develops. Water blisters consist of a soft, watery rot of the fruit flesh with overlying skin glassy, water-soaked and brittle. Eventually, the skin, flesh and core disintegrate and the fruit dries out, leaving an empty fruit carcass containing a few, black vascular fibres. The fungus enters the fruit through wounds and the crevices between individual fruits.
- Use healthy sets of an appropriate physiological age to ensure rapid germination.
- Choose sets with at least 3 nodes to increase the likelihood that the buds towards the centre will germinate before the fungus invades all the tissues.
- Use crop management practices that promote germination and rooting. In disease prone areas, if possible, plant varieties that are quick to germinate. Varieties that are slow to germinate should be treated in hot water (50 °C for 2 hours).
- Avoid extremely wet or dry soil conditions.
- Do not plant freshly cut planting material unless dried out.
- To prevent the spread of the pathogen, avoid wounds to tissue and remove infected pineapple plants.
- Improve soil drainage and avoid planting during wet weather.