Insects, Pests and Disease Control : Pineapple

Pineapples rarely suffer from pests and diseases when good growth conditions have been cared for. The following diseases and pests occur especially in systems which lack diversification.

7.1 Pineapple Mealybug Wilt-associated closterovirus (PMWaV)

1. Symptoms:

• Infected plants become yellowish-red to bright red at the leaf tips, this coloration spreading down the leaf with time.
• Soon other leaves turn colour and also show signs of wilting.
• The inner heart leaves remain normal.
• Severely infected plants become stunted and produce small, under-grade and immature fruits.

• The first effect of the disease usually appears in the roots, which stop growing, collapse and then rot; this results in leaves symptoms similar to the effect of drought.
• The disease is probably introduced in planting material, which may not show obvious disease symptoms. Once established, it is spread by mealybugs, sedentary insects, which are moved from plant to plant by attendant ants.

1. Management:

• Use planting material from wilt-free areas.
• Heating pineapple crowns in a large water bath at 50°C for 30 minutes enables 100% plant survival and renders 100% of the plants free of pineapple wilt-associated virus.
• Growth of the heat-treated plants is more rapid than in non-heat-treated plants.
•  Plant resistant varieties if available. Some varieties of pineapple are more resistant to the virus than others, the variety Cayenne (and 'Masmerah') being highly susceptible. ‘Spanish’ shows some resistance.

7.2. Pineapple mealybug (Dysmicoccus brevipes)

1. Symptoms:

• The mealybugs are oval, pink in color, up to 3 mm long, covered with a whitish waxy secretion, which develops into waxy filaments around the body.
• This mealybug is the most serious pest of pineapples, because it is a vector of the Mealybug or Pineapple Wilt Virus.
• The mealybug is common on the roots of pineapple and large colonies develop on the stems just above ground level.
• The mealybugs may spread upwards to feed in the floral cavities, on both small and mature fruit, and on the crown leaves.
• Heavy infestations are conspicuous because of the white waxy adults, which often occur at the growing points, around the stem nodes, on the undersides of leaves, on the fruit and on the roots.

Picture showing severe infestation of pineapple mealybug on the fruit

1. Management:

• Control ants to give a chance to natural enemies to keep mealybugs under control.
• See also what to do by pineapple wilt virus, specified above.

1. Yellow spot virus:
2. Syptoms:

• The yellow spot virus has been shown to be identical to the tomato spotted wilt virus.
• It infects over a 100 species of plants including peppers, tomato, tobacco, eggplant, potato, broad bean, spinach, chicory and peas.
• A number of wild plants, including some common weeds such as the black jack (Bidens pilosa) and Datura stramonium, are also host of this virus. Thrips are vectors of this virus.
• When host plants of the virus are grown near to pineapple plants, the incidence of the yellow spot virus is considerable enhanced due to thrips migrating into the pineapple field.
• Wind carries thrips long distances and thus also plays an important role in the transmission of the virus.
• Symptoms in the fruit is a blackened, dry cavity in the side of the fruit due to one or more "eyes" having died.
• Thrips feeding on the crown of fruits results in concentric ring patterns developing on crown leaves

1. Management:

• Control weeds in and around pineapple fields. This is very important for disease control because the presence of certain weeds leads to increased number of thrips.
• Cut off the fruits showing early symptoms of infection. This will prevent the spread of infections into the fruits.
• Where this disease is a problem avoid planting near host plants of the thrips and the virus.
• Even if thrips are not strongly inclined to migrate from their favored host plants, they will do so if disturbed, for instance by human passing, animals or machinery.
• Control thrips.

1.  Thrips (Thrips tabaci and Frankliniella schultzei)
2. Symptoms:

• The blossom thrips feeds mainly on flowers and its feeding results in the development of "dead-eye" in the fruit.
• Thrips feeding on the crown of fruits results in concentric ring patterns developing on crown leaves.

1. Management:

• Control weeds in and around pineapple as certain weeds leads to increased number of thrips.
• Remove heavily infested plant material.
• Control thrips in the early stages, in particular immature thrips; adult thrips are unable to pick the virus from infected plants.  Once the immature thrips are infected with the virus they remain vectors for the rest of their lives.
• Spray with insecticide (Lambda-Cyhalothrin,... (1ml/1L of water).
• Also a garlic bulb extract can be sprayed thoroughly on the whole plant, preferably early in the morning. Spraying should be particularly directed to the neck area of the plant for good penetration into the plant.

7.5. Pineapple top and root rot

1. symptoms :

• The leaf edges curve back and leaves are easily pulled out from the plant.
• Internally, the stem and leaf bases become soft, rotten and have an unpleasant smell.
• The growing point of the stem has a cheese-like appearance.
• It is common in young plants of 3-8 months. 
• Splashing rain, irrigation water and biting insects act as agents to spread disease.

1. Management:

• Do not plant pineapples in soils prone to waterlogging.
• Ensure good drainage.
• Improve soil by selective fruit rotations and application of organic compost material.
• Avoid overhead irrigation.
• Control insect pests.
• Planting materials can be dipped in copper fungicides before planting or use resistant plants.
• Fungicides can be used to control any fungal complications.

7.6. Black rot of pineapple (Ceratocystis paradoxa)

1. Syptoms:

• White leaf spots are yellow to brown and several cm long.
•  Later they dry to become papery and straw colored.
• 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 colored mycelium develops.

1. Management:

• 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 two hours).
• Avoid extremely wet or dry soil conditions.
• Do not plant freshly cut pineapples 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.