Plant parasitic nematode, the hidden enemy of crops is one of the many groups of harmful organism which depend on plants for their survival. Nematode can cause damage to almost all kinds of crops, however, due to their subterranean habit, microscopic size (from 0.3 to 10 mm length), they are invisible to the naked eye. They penetrate and feed on the root of growing plants, stealing nutrients vital for plant growth and exposing the roots to attack by other soil pathogens. It has widely been recognized that plant parasitic nematodes constitute one of the most devastating pests groups and are responsible for insidious disease symptoms in different crops causing huge losses. Estimated annual yield losses in the world’s major crops due to plant parasitic nematodes is about 12.3% and it is about 14% in the developing countries (Sasser & Freckman, 1987). In India, recent estimate showed nematode is responsible for both quantitatively and qualitatively yield losses amounting about Rs.240 billion every year (Sehgal & Gaur 1999). Beside direct damage, plant parasitic nematodes serve as predisposing agents in development of disease complexes with fungi, bacteria and viruses. In many situations, plant varieties resistant to fungi, bacteria are rendered susceptible when parasitized by nematodes. There is no doubt that nematodes either alone or in combination with other pathogens constitute an important constraint to world food production. Intensive and extensive cultivation of crops particularly in irrigated crop production system has seriously aggravated nematode problems in various crops. The hidden nature of nematode causing damage out of sight of farmers, scientists and non specific disease symptoms in the above ground parts of the crops are perhaps main reasons why so little attention has been given to the hidden pest of crops.
It is one of the serious nematode pests of potato in some southern states like Tamil Nadu, Karnataka, and Kerala. The nematode is popularly known as ‘golden nematode’ and has been recognized as one of the major crop protection problems of the world. The nematodes are responsible for average losses of 9% of global potato amounting to about 40 million tons (Krishna Prasad, 1995).
In potato cyst nematode is known since 1961 when F.G. Jones detected this nematode from a field at Vijayanagaram state farm in Ootacmund of Nilgiri Hills in Tamil Nadu. Considering importance of potato cyst nematode in the country, the Government of Tamil Nadu imposed the Destructive Insect Pest Act 1919(DIP Act 1919) in 1971 to contain the nematode in the Nilgiri Hills. It is difficult to detect the disease symptoms at low infestation of nematode but the symptoms are prominent only after the build up of population in soil. The disease symptoms appears in small patches of poorly growing plants, temporary wilt of plants in day time, stunted plants, unhealthy yellowish foliage and poor root systems, reduction of number and size of tubers and production of potato yield gradually reduced over the years. The nematode is primarily confined to the family solanaceae and depends on the host root diffusates which induce the hatching of second stage juveniles from eggs.
The second stage juveniles infect the root and modify the cells as giant cell for ensuring permanent nourishment to reach adult stage. The adult females are white spherical shape which is found attached with root and after death of female turn into brown cyst. All the eggs laid by the females are retained inside the body. This cyst containing eggs are protected and remain viable for several years in soil even in the absence of potato. The pathotypes RO1 and RO5 of G. rostochiensis and Pa2 and Pa3 of G. pallida of potato cyst nematodes are known to be prevalent in India.The nematode cyst containing eggs are generally spread through soil particles adhering to tubers, farm implements, gunny bags, farmers’ feet etc. However, irrigation water or rain water running down the hill slope carry the cyst from the infested field to uninfested fields.Management options
Plant parasitic nematode, the hidden enemy of crops is one of the many groups of harmful organism which depend on plants for their survival. Nematode can cause damage to almost all kinds of crops, however, due to their subterranean habit, microscopic size (from 0.3 to 10 mm length), they are invisible to the naked eye. They penetrate and feed on the root of growing plants, stealing nutrients vital for plant growth and exposing the roots to attack by other soil pathogens. It has widely been recognized that plant parasitic nematodes constitute one of the most devastating pests groups and are responsible for insidious disease symptoms in different crops causing huge losses. Estimated annual yield losses in the world’s major crops due to plant parasitic nematodes is about 12.3% and it is about 14% in the developing countries (Sasser & Freckman, 1987). In India, recent estimate showed nematode is responsible for both quantitatively and qualitatively yield losses amounting about Rs.240 billion every year (Sehgal & Gaur 1999). Beside direct damage, plant parasitic nematodes serve as predisposing agents in development of disease complexes with fungi, bacteria and viruses. In many situations, plant varieties resistant to fungi, bacteria are rendered susceptible when parasitized by nematodes. There is no doubt that nematodes either alone or in combination with other pathogens constitute an important constraint to world food production. Intensive and extensive cultivation of crops particularly in irrigated crop production system has seriously aggravated nematode problems in various crops. The hidden nature of nematode causing damage out of sight of farmers, scientists and non specific disease symptoms in the above ground parts of the crops are perhaps main reasons why so little attention has been given to the hidden pest of crops.
