Burrowing nematode or Banana-root nematode (Radopholus similis) is an important parasite of fruit, vegetable, and other crops. It is an especially important pest of banana

Banana

Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

s and citrus

Citrus

Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...

, but it will also attack coconut

Coconut

The coconut palm, Cocos nucifera, is a member of the family Arecaceae . It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word...

, avocado

Avocado

The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...

, coffee

Coffea arabica

Coffea arabica is a species of Coffea originally indigenous to the mountains of Yemen in the Arabian Peninsula, hence its name, and also from the southwestern highlands of Ethiopia and southeastern Sudan. It is also known as the "coffee shrub of Arabia", "mountain coffee" or "arabica coffee"...

, sugarcane

Sugarcane

Sugarcane refers to any of six to 37 species of tall perennial grasses of the genus Saccharum . Native to the warm temperate to tropical regions of South Asia, they have stout, jointed, fibrous stalks that are rich in sugar, and measure two to six metres tall...

, and assorted other types of grasses

Poaceae

The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...

 and ornamentals

Ornamental plant

Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

. It is a migratory endoparasite of root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s. The nematode causes a lesion on the plant's root that forms a canker

Canker

Canker and anthracnose are general terms for a large number of different plant diseases, characterised by broadly similar symptoms including the appearance of small areas of dead tissue, which grow slowly, often over a period of years. Some are of only minor consequence, but others are ultimately...

, and the plant suffers from malnutrition

Malnutrition

Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....

while the nematode completes its life cycle within the root.

History and significance

First described by Nathan A. Cobb in necrotic tissue of the roots of Musa sp in 1891, Radopholus similis (Burrowing nematode) is one of the most important root pathogens attacking bananas ^[1]. This nematode is widespread and can cause yield losses of up to 30-60% in many countries ^[2].

Distribution

Widespread in most banana-growing regions of the world and present in glasshouses in temperate areas such as: Asia, Africa, North America, Central America and Caribbean, South America and Oceania ^[1].

Morphology

All nematode stages are vermiform. Adult males and females are different in appearance (sexual dimorphism), the males having poorly developed stylets and a knob-like head caused by an elevated, constricted lip region. Both males and females have long, tapered tails with rounded or indented ends. The male has a sharp, curved spicule enclosed in a bursa, or sac. Females are between 550 and 880 µm (0.55 to 0.88 mm) in length and about 24 µm in diameter, with well-developed stylets 16 to 21 µm (average 18 µm) long. Males are smaller than females, 500 to 600 µm in length ^[5].

Life cycle

Radopholus similis is a migratory endoparasitic nematode which completes its life-cycle in about 21 days at 25ºC in the root corm tissues ^[4]. Females and juvenile stages both attack and enter host roots, especially near the tip of the roots. Males with their weak stylets do not feed. Females lays an average of four to 2-6 eggs each day ^[5].

Host parasite relationship

The disease caused by R. similis is called toppling or blackhead disease ^[3]. As the nematodes feed they destroy anchor roots and make banana plants susceptible to toppling. Furthermore, roots damaged by nematodes cannot supply plants with needed water and nutrients, resulting in reduction of plant growth and development ^[4].

Management

Management of R. similis consist in reduce nematode populations in the soil before planting, for example using soil fumigation, removing host and doing rotation with non-host crops and also planting cover crops such as Crotalaria or Tagetes. Furthermore, before planting pared the rhizomes in order to remove dark spots (infections), then soak them in hot water (125ºF) for 20 minutes. Although those practices can reduce nematodes population, plants from tissue culture raised in a disease-free nursery are the best option ^[4].

External links

• Info about Radopholus similis on Musapedia