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Seasonal Population Fluctuations of Cowpea Aphid Aphis Craccivora Koch and its Predatory Coccinellids

  • J. Srikanth
  • N. H. Lakkundi
Research Article

Abstract

In two study seasons, viz. summer (March to May) and “kharlf” (August to October) 1984 at Bangalore, India, populations of Aphis craccivora Koch on cowpea increased rapidly with crop growth and their peak coincided with peak pod formation. The activity of predatory coccinellids started 1 to 3 weeks after the appearance of aphids. The peak predator population more or less coincided with the peak aphid population. Highly significant positive correlations were found between weekly aphid and predator populations in the two seasons. The prey to predator ratio reached higher values 2 weeks after the incidence of the aphid, during peak pod formation stage and at the time of harvest. Amongst the predatory coccinellids, Menochilus sexmaculatus (F.) was predominant in both seasons constituting 77–88% and 83–95% of total predator population during summer and “kharif”, respectively. The study demonstrated a prey-dependent predator growth, often lagging behind that of the prey, pressing the need for alternate control methods that can be integrated into the management strategy considering the weather factors such as rainfall.

Key Words

Cowpea aphid Aphis craccivora Koch predatory coccinellids Menochilus sexmaculatus (F.) population fluctuations 

Résumé

Une etude faite en ètè (Mars-Mai) et entre les mois d’Avril et Octobre 1984 a Bangalore en Inde sur les populations d’Aphis craccivora Koch sur les pois a donné les resultats suivants. Les populations d’A. craccivora Koch augmentaient rapidement avec les cultures en croissance et que d’autre part les pics des insects coincidaient avec ceux de la formation de la cosse de cette plante. L’activité de coccinellides connu comme predateur commencait une à deux semaines après l’apparence des aphides. Le pic de la population des predateurs coincidait avec celui de la population des aphides. Des correlations significatives et positives entre les populations d’aphides et de predateurs pendant une semaine existaient durant les deux saisons. La proportion entre la proie et le predateur a atteint les valeurs maximales deux semaines après l’incidence des aphides, pendant le stage de la formation des cosses ainsi que pendant la recolte. Parmis les coccinellides predateurs-Menochilus sexmaculatus (F.) etait predominant pendant les deux saisons et constituaient respectivement 77-88% et 83-95% de la population totale des predateurs. Cette etude demontra une croissance des predateurs dependante de celle de la proie. Des strategies nouvelles sont necessaires pour lutter contre l’A. craccivora Koch parceque leur nombre croit plus vite que celui du predateur.

Mots Clefs

Aphides Aphis craccivora Koch pois coccinellides predateurs Menochilus sexmaculatus (F.) fluctuation de la population 

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Copyright information

© ICIPE-ICIPE Science Press 1990

Authors and Affiliations

  • J. Srikanth
    • 1
  • N. H. Lakkundi
    • 1
  1. 1.Department of EntomologyUniversity of Agricultural Sciences G.K.V.K.BangaloreIndia

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