Insect Pests of Fruit, Plantation, Medicinal & Aromatic Crops (2+1)

2. Root lesion nematode

• Plant parasitic nematodes are microscopic ‘round worms’ attacking almost every crop.
• The root lesion nematode is highly distractive to Arabica coffee.
• Robusta is tolerant to Arabica coffee. Robusta is tolerant to nematodes.
Life History

• The nematode lays eggs in the root-lesions. Development from egg to adult takes about a month.
• All stages of the nematodes are attracted to the young and vigorously growing roots but only the second stage juveniles enter the roots at the piliferous zone.
• Robusta exhibits tolerance to the nematodes at all stages, and the nematode takes more time to complete its life cycle in robusta than in Arabica.
• The nematode spreads to other areas through estate implements, rain water, plants taken from the infested nurseries and soils taken from infested blocks.
• The pest is persistent in the soil and roots all round the year. Higher population is noticed during the months of July, August and September when there is heavy rainfall and increased root activity.
• The population declines from December to March.
• Damage and symptoms of attack
• Nematodes feed and destroy the tap root, secondary roots and feeder roots.
• Affected plants put forth adventitious roots at the collar region during rainy season.
• Such plants have loose anchorage and could be easily dislodged.
• Affected old plants lack secondary and tertiary roots.
• Affected young plants become unhealthy with lean and lanky stem.
• Older leaves become yellow and drop, leaving very few undersized, chlorite and crinkled leaves at the tip of the main stem giving a ‘tufted’ appearance.
• Affected bearing plants show thinner main stem and have inadequate foliage to support the crop.
• Fresh leaves produced during pre-monsoon period are smaller, crinkled, chlorotic and leathery, but the leaves produced during monsoon are normal and healthy.
• Death of leaves will continue till December, leaving one or two pairs of leaves at the tip during next summer or producing a ‘goose-neck’ after the receipt of rains.
Control Measures

• In The Nursery
• Dig up the nursery site and expose the soil to the sun during summer.
• Sieve and dry jungle soil and farmyard manure thoroughly before use.
• Avoid obtaining nursery plants from infested areas.
• In The Filed
• Uproot and burn the affected plants.
• Dig up pits and expose the soil to the sun for at least one summer
• Take care to keep the pits free from weeds.
• Plant the area with Robusta (if suitable) or Arabica – Robusta grafted plants (Arabica scion grafted on to Robusta root stock at ‘topee’ stage)