|
| << previous | next >> |
Journal description
All volumes of the corresponding journal
All issues of the corresponding volume
All articles of the corresponding issues
Details for article 14 of 16 found articles
| Title: |
Natural Control of Helicoverpa armigera in Sunflower: Assessment of the Role of Predation |
| Author: |
Van Denberg, H. Cock, M. J. W. Oduor, G. I. |
| Appeared in: |
Biocontrol science and technology |
| Paging: | Volume 7 (1997) nr. 4 pages 613-630 |
| Year: |
1997-12-01 |
| Contents: |
In three field experiments in Kenya , the seasonal population trend of Helicoverpa armigera (Hubner) (= Heliothis armigera) in sunflower was followed in plots from which predators were excluded and in plots from which predators were not excluded . In experiment 1 , complete exclusion of crawling predators (predominantly Pheidole spp . of ants occurring at densities of 25 per plant) resulted in H. armigera densities 3 - 5 times higher than in plots where ants were not excluded . Pheidole sp . had more impact on young H. armigera larvae (instars 2 - 3) than on older larvae (instars 4 - 6) . The results of experiment 2 were less striking , because H. armigera infestation was low , and ant densities were moderate . Here , Myrmicaria spp . and Camponotus spp . were the predominant ants . Exclusion of ants resulted in a 1 . 8 - fold increase in densities of large H. armigera instars . In experiment 3 , the impact of predators on H. armigera was studied under three conditions: exclusion of crawling predators , exclusion of both crawling and flying predators , and the control where no predators were excluded . To evaluate the role of predation in total mortality , the recruitment of H. armigera larvae was determined with Southwood and Jepson ' s graphical method , and recruitment of newly laid eggs was directly measured on trap plants . Because it was difficult to detect older eggs due to colour change , the direct measurement of egg recruitment was superior to the graphical method . Ants and Anthocoridae were the dominant predators . M ortality from egg to older larvae (instars 4 - 6) was 73 - 78% . Exclusion of ants and anthocorids did not affect the densities of H. armigera larvae . Anthocorid predators increased only after the main oviposi tion peak of H. armigera and , therefore , their exclusion had little impact on the pest . Ant density was considerably lower than in experiment 1 , and did not significantly suppress H. armigera. |
| Publisher: |
Taylor & Francis |
| Source file: |
Elektronische Wetenschappelijke Tijdschriften |
Details for article 14 of 16 found articles
| << previous | next >> |