Diseases

A. Category : Bacterial

1. a) Bacterial heart rot and fruit collapse: Erwinia chrysanthemi

Symptoms

• Water-soaked lesions on the white basal sections of leaves in the central whorl which may spread to all leaves in the central whorl; midportions of leaves become olive green in color with a bloated appearance; infected fruits exude juices and the shell becomes olive green; cavities form within the fruit

Cause

• Bacterium

Comments

• Disease is thought to be spread from the juices of infected fruits; bacteria in the juice can enter leaves through wounds; ants acts as vectors for the bacteria

Management

• Remove and destroy infected fruits; avoid the use of infected crowns for seed material to prevent spread of the disease; planting to avoid flowering when adjacent field is fruiting can reduce disease development; use of miticides and control of ants can significantly reduce disease incidence

B. Category : Fungal

a) Butt rot, Black rot & White leaf spot Chalara paradoxa

Symptoms

• Soft black rot which begins at the area where the seed piece detaches from the mother plant; entire seed piece may be rotted; black rot of fruit causes a soft, watery rot which darkens with time; small brown, wet spots develop on leaves; leaf spots enlarge and turn gray-brown with light brown margins

Cause

• Fungus

Comments

• Fungus survives in soil and pineapple residue; infects plants through fresh wounds

Management

• Seed material should be stored on mother plants during dry weather and with good air circulation; freshly removed seed material should be dipped in an appropriate fungicide within 12 hours of removal from the mother plant; avoiding bruising and wounding of fruit during harvest helps to reduce black rot; harvested fruit should be dipped in an appropriate fungicide within 6-12 hours of harvest to prevent disease development during shipping

C.  Category : Other

a) Marbling Acetobacter spp.

b) Erwinia herbicola

Symptoms

• Yellow to red or very dark brown discoloration of fruit flesh; infected tissues develop a granular texture with woody consistency and speckled color; single or multiple fruitlets may be affected; vascular system may appear speckled right down to core of fruit; symptoms develop during the last month of fruit maturation

Cause

• Bacteria

Comments

• Emergence of the disease is favored by warm, wet weather

Management

• There are currently no methods of controlling the disease; the pineapple variety Smooth Cayenne appears to be moderately resistant to the disease

D. Category : Viral

a) Mealybug wilt Pineapple wilt virus (PWV)

Symptoms

• Leaves turning red; tips of leaves become withered and turn brown; plants can be easily removed from the soil

Cause

• Virus

Comments

• Virus is transmitted by mealybugs; ants protect mealybug populations from predators and parasites and can allow mealybugs populations to reach very damaging levels if left uncontrolled

Management

• Ants should be controlled with an appropriate insecticide

E. Category : Oomycete

a) Phytophthora heart and root rot Phytophthora spp.

b) Pineapple heart rot

Symptoms

• Young leaves failing to elongate and turning chlorotic; heart leaves wilting and turning brown; terminal whorl can be easily pulled from mother plant; water-soaked tissue at base of leaves; foul smell; leaves may be turning red and yellow with necrotic leaf margins and leaf tips; plants can easily be pulled out of the ground; fruits color prematurely

Cause

• Oomycete

Comments

• Fungi can survive in soil and plant debris for many years

Management

• Planting in raised beds helps to drain the soil and reduces incidence of the disease; mulch from pineapple debris should be avoided; pre-planting dips and foliar applications of Fosetyl Al are very effective at controlling the disease