Organization: Instituto Tecnologico de Veracruz (http://www.itver.edu.mx)
Authors: J. De La Cruz Medina and H.S. García
Edited by: Danilo Mejía, PhD - Agricultural and Food Engineering Technologies Service (AGST)
CHAPTER XXXIII: Pineapple post-harvest operations
DISEASES AND PLAGUES
Rotting caused by the cottony wood-louse is the most widely spread and harmful disease in pineapple culture mainly for the cultivar “Smooth Cayenne”. A quick expansion occurs from the initial infestation point. As soon as symptoms appear the insects invade healthy plants. Roots stop growing, then collapse and rot, causing plant fading. The plague starts at the tips of the leaves (Fig. 32), which develop a yellow-red color. Control of cottony wood-louse is essential but it can only be achieved if the related ants are eliminated, for which periodical insecticide (Parathion) spraying. The “Smooth Cayenne” cultivar is very susceptible to fading, although some resistant clones have appeared. Cultivars “Red Spanish” and “Singapore Spanish” are used for genetic improvement due to their resistance. The actual cause of the disease appears to be a virus, but nobody has proven it yet. The yellow spot has been associated with a transmitted virus. The inoculum is an adventitious of the family of weed Emilia sonchifolia. The only way of control is by suppression of the weed. Nematodes may be found in excess of 100.000/cm3 of soil and are one of pineapples worst enemies. Nematodes infect roots producing tonsils (Meloidogyne) and lesions (Pratylenchus), or can penetrate directly the roots (Rotylenchus). Other genera have also been found to be involved. Nematodes usually prefer light soils, although they may also be found in common and clay-type soils. In the first 3-4 months after ground clean up and planting, the count of nematodes is low, but then populations raise steeply, and growth of Ananas plants are severily hindered, with the appearance of chlorotic leaves. Then, the number of nematodes drops abruptly in a similar way as in drought conditions. This oscillating trend is more marked in short cycles as those of export. All vegetative material capable of hosting nematodes shall be destroyed before planting. (Infoagro.com. 2002).
Two weeks prior to planting, soil may be fumigated with D-D (300 L/Ha), but this compound is too toxic for the plant. EDB (ethylene dibromide) when applied at 100 kg/Ha, decrease phytotoxicity problems. Fumigation may increase crop yield from 3 % to 32 %, depending on the abundance of nematodes at the moment. It is advisable to fumigate only when strictly necessary, since is an expensive and dangerous procedure. Another promising nematocide is Oxamilo, which can be ground and unlike the other active compounds it is transported donwards from leaves to roots. Nevertheless before a product is applied one has to make sure that its use has been approved and be aware of potential problems caused by its residues. It is recommended to allow the soil to rest for six months so that nematodes may be eliminated. This is a very expensive method and can hardly be considered. Sinfilides are miriapodes that may turn disastrous in pineapple plantations. They are ca. 4 mm long and feed on roots. As a reaction to the invasion, roots turn into a broom shape, their radicular system is downsized and becomes prone to fungal attack and the plant stops its growth. The above mentioned fumigants are active against this plague, but the use of Lindane (2 kg active compound/Ha) acts as reinforcer. Fenamifos and Etoprofos can be used too. Other plagues affecting pineapple culture are mites (Fig. 33), fruit flies, the moth Castnia licus (same as in bananas) and the butterfly Thecla basilides. The latter can only be controlled after hormonal treatment. The heart rot is caused by Phytophthora cinnamomi and by P. parasitica in warm regions. Their zoospores are chemically transferred to the trichomes and penetrate the cells of young leaves. In order to control the disease the vegetative material can be immersed in Difolatan, although other authors prefer Metalaxil and Aliette. It is also recommended ground Captafol at a rate of 2 % on 3.500 L/Ha, applied immediately after planting, one months later and one week after the treatment for flowering induction. Thielaviopsis paradoxa causes rotting of plant material for planting and of fruits post-harvest. Prevention is done by immersion of the stem in benzoic acid, Shirlan or Imazalil. Fruit gomosis is produced “Red Spanish” cultivar, while cultivar “Smooth Cayenne” is resistant. It seems to be caused by caterpillar feeding and can be controlled by ground insecticide application (Infoagro.com. 2002).
Brown spot
Fig. 32 Pests and diseases in pineapple plant and fruit (SARH, 1994)
Fig. 33 pineapple plague (SARH, 1994
