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Wageningen Universiteit (1993)

Natural control of Helicoverpa armigera in smallholder crops in East Africa

Berg, H. van den

Titre : Natural control of Helicoverpa armigera in smallholder crops in East Africa

Auteur : Berg, H. van den

Université de soutenance  : Wageningen Universiteit

Grade : PhD thesis 1993

Présentation
The African bollworm, Helicoverpa (=Heliothis) armigera , is one of the worst agricultural pests in Africa, attacking a variety of food and cash crops. For development of sustainable pest management, it is essential to study the ecology and natural mortality factors of the pest, and recently, the need for the assessment of the role of natural enemies, through life table studies, has been stressed in a number of workshops that focussed on the pest.
Information available on the natural enemies of H.armigera, in Africa is reviewed, using published, unpublished and museum sources (Chapter 3). A large variety of natural enemies is represented in almost 300 host records, including 83 parasitoids identified to species and 93 identified only to genus. The taxonomy, distribution, biology, alternative hosts or prey, host plant associations and secondary natural enemies are detailed for all recorded natural enemies, and the different aspects are summarized and evaluated for the total natural enemy complex.
During the three-year research programme reported here, H.armigera was studied in four crops commonly grown in smallholdings in Kenya : cotton, sunflower, maize and sorghum. The incidence of the pest varied widely between seven experimental sites in different agricultural zones of Kenya (Fig. 4.1). H. armigera , only occasionally reached damaging levels. A number of parasitoids was recorded, but their impact on H. armigera was generally low ; Trichogrammatoidea spp. egg parasitoids and Linnaemya longirostris, a tachinid late-larval parasitoid, were the most common species. Two groups of predators were predominant throughout Kenya : Anthocoridae (mainly Orius spp.) and ants ( Pheidole spp., Myrmicaria spp. and Camponotus spp.), but their abundance fluctuated widely between sites (Fig. 4.3). Pathogens were scarce and did not play a significant role.

Mots clés : insects / plant pests / noctuidae / plant protection / biological control / animals / population density / population ecology / mortality / population growth / east africa / helicoverpa armigera / helicoverpa

Résumé de la thèse

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