Pest :Coreid bug (Nut crinkler)

Paradasynus rostratus Coreidae

The pest appears in different intensities causing severe damage in some pockets. Adult is a large coreid bug.It can be identified with its reddish brown body above and pale beneath.Male is smaller than female.Eggs are usually laid in lines in young nuts, inflorescence, spathe and sometimes on leaves.The bug lays about 40-60 eggs. Eggs hatch in 8-10 days.Emerging nymphs are ant like and can be identified by its piercing mouth parts. Nymphs are reddish brown.Young nymphs on emergence rest in groups in young nuts. Nymphs after moulting reach second stage and they also rest in nuts in groups.

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Symptoms

  • The bugs and their nymphs feed from the inflorescence, young nuts and tender coconut by piercing and sucking the juice.
  • The damage to nuts varies depending upon the point at which the insect pierces for feeding.
  • If the feeding point is just below the perianth such nuts fall down in due course.
  • During feeding, the bug injects a toxin due to which the cells of the nut get damaged resulting in nut fall.
  • When such fallen nut is examined after removing the perianth development of cracks can be seen due to feeding injury.
  • If the feeding point is just below the perianth such nuts do not fall and develop in to mature nuts and in such cases the developing nuts remain crinkled.
  • These damaged areas exhibit furrows with gummosis.
  • The damaged nuts which are retained on the tree will develop in to under sized or barren nuts.
  • The husk of the crinkled nuts become hardened and cause difficulty in dehusking.
  • The copra content is also reduced which in turn affects the market value. If the attack is severe the % of barren nuts will increase.

Procedure for Observation

The population of coreid bugs start during June and reaches its peak during September-October and then decline.Select 20 trees at random from a plot and collect the fallen nuts and look for the symptoms of damage after removing the perianth. Record the average damaged nuts per tree. Less than 5 damaged nut : mild, 5-10 moderate and > 10 severe.

ETL

10 damaged nuts.

Control Measures

  • Chrysochacissa oviceps (Torymidae) and Grayon homoeceri (Scelionidae) are egg parasites of the bugs.
  • Guava, neem, cocoa are alternate hosts of the pests, hence measures adopted to control pests in coconut palms should also be carried out on the alternate hosts.
  • Apply 0.1% carbaryl 50 WP or quinalphos 25 EC 0.05% on the entire crown, excluding the newly opened inflorescence, the leaves and old bunches.
  • Spraying may be carried out three times in a year during the beginning of June, September-October and also during November on need base.
  • Spraying insecticides should be done during evening to avoid disturbances to honey bees.