Pest:Pea Aphid

Aphis craccivora

Aphididae

Amaranthus aphid adults are shiny greenish black while nymphs are slightly grey. The appendages are usually whitish with black tips. Aphid lives throughout the year without producing sexual forms. They are either apterous or winged ones and parthenogenetic. It is a polyphagous species infesting cow pea, other pulses and leguminous crops. Life cycle is completed within eight days. The reproductive phase of the aphid lasts for seven days. During this period 14-17 off springs are produced per female.

A dry spell following heavy rain is favourable for rapid build up of aphid population. The pest population and its predators are high from September to April. In the field population of the aphid is governed by the interaction of climate and natural enemies.

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Symptoms

  • The aphid infestation in a field is typically patchy.
  • The adults and nymphs suck sap from different parts of the plant namely underside of leaves, terminal shoots, stem and branches, flower stalks and pods.
  • The Cow pea aphid inject a powerful toxin in to the plant while feeding. Feeding damage is expressed as yellowish hue on the infested leaves.
  • Adult prefer to feed on the dorsal surface of the leaves by scraping linear streaks.They also feed on the ventral leaf surfaces rarely.
  • The growth of the plant is greatly retarded resulting in stunting of the plant.
  • The pods become malformed.The aphids produce considerable amount of honeydew upon which sooty mould fungus grows affecting the photosynthetic ability of the plant.
  • More honey dew excretion make the surface sticky. The aphid transmit Amaranthus mosaic virus.

Procedure for Observation

Select five plants at random and assess the total number of Aphds in 5 cm length of the affected portion. Take the average. Less than 5 mild 5-10 moderate,more than 10 severe.

ETL

  • 5 Aphids.

    • Control Measures

  • Hyptis suaveolens (Vilai thulasi/Nattapoochedi/Chadayan) extract (One litre leaf extract plus 60 g ordinary soap diluted in half liter of water) This stock solution is to be diluted with 15 liters of water before spraying.
  • Spray tobacco decoction (one liter of the prepared decoction to be diluted in six liters of water) or neem seed kernel extract 5% or 2% neem seed oil emulsion plus garlic extract.
  • Encourage predatory lady bird beetles such as Scymnus nubilus, Pseudaspidimerus circumflexa, Micraspis crocea,Menochilus sexmaculatus, the Syrphids such as Parargus serratus, Ascarina sp and Ichiodon scutellaris and an Hemerobiid .
  • Spray insecticides such as 0.1% malathion or 0.05% quinalphos . Since harvesting of Amaranthus is done usually once in two days spraying insecticides should be avoided when the crop reaches fruiting stage.
  • Spray Verticillium lecanii to manage residual population (5 ml or 20 g /L).