INSECT PESTS OF CRUCIFEROUS CROPS

INSECT PESTS OF CRUCIFEROUS CROPS

1. Diamondback moth, Plutella xylostella (Yponomeutidae : Lepidoptera)

Distribution:
Cosmopolitan

Hosts: All cruciferous crops, also reported from Solanaceous and Liliaceous plants.

Nature of damage:
  • Young caterpillars scrap epidermal leaf tissue, producing typical white patches.
  • Older larvae bite holes on the leaves.
  • The infestation is more severe in dry season, when it causes growth retardation (under sized heads).

6.1

Identification:
  • Egg: Yellowish white with greenish tinge.
  • Larva: Full grown larvae are 8-12 mm long, green in colour
  • Pupa: pupate in silken cocoon which is about 20 mm
  • Adult: 8-10 mm, grayish brown having pale white narrow wings with inner margins yellow. 3 pale white triangular markings on hind margins of each fore wing which appears as three diamond shaped spots when at rest

6.2

Life cycle:
  • Incubation period 3-8 days
  • Larval period 10-30 days
  • Pupal period 7-14 days
  • Total life cycle 4-5 weeks.
  • Adult longevity 16-18 days.
  • There are 8-10 generations in a year.
Salient features:
  • Lay eggs singly or in clusters of 2-40 glued to the ventral surface of the leaf.
  • Each female lays 20-300 eggs
  • Pest is active during winter in plains, where as in hills it is active from March-April to October- November.
  • Moths hide under the remnants of plants during winter.
Management:
  • Indian mustard as trap crop
  • Removal and destruction of plant debris after harvest and ploughing
  • Intercropping with tomato or carrot reduces the incidence.
  • NSKE @ 4.0 per cent and Bt formulation (Halt/ Dipel) @ 500g/ ha are also effective against the DBM.
  • Periodic releases of Trichogramma brassicae @ 100000/ha
  • Larval parasitoid, Diadegma semiclausm in nature.
  • Need based use of insecticides like fenvalerate (0.01%) or cypermethrin (0.0075%) or deltamethrin (0.0028%) can also be used if population persists.
Last modified: Wednesday, 7 March 2012, 6:22 AM