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Tri-tropic-level interactions between herbivorous insects and their natural enemies

Tri-tropic-level interactions between herbivorous insects and their natural enemies
Tri-tropic-level interactions between herbivorous insects and their natural enemies

The ultimate objective of crop protection is to achieve high yield. To do so many control measures, including the application of harmful pesticides are used to combat pest problems, but in most cases the role of the plant itself (first trophic level), and that of the parasitoids and predators (third trophic level) are ignored. Natural enemies have a tremendous influence on herbivores (second trophic level). In this project the role of each of these trophic levels was evaluated. Prior mechanical damage to the leaves of tomato (Lycopersicon esculentum) and oilseed rape (Brassica napus) deterred herbivore (Spodoptera littoralis) feeding and affected the distribution of grazing damage between upper and lower leaves of the plants. The percentage leaf area eaten by the larvae of S.littoralis in the wounded leaves of tomato and oilseed rape in the presence of the soil-dwelling insect predator (Pterostichus melanarius) was significantly lower than that of the unwounded leaves in the absence of predators.

Rearing of the grain aphid Sitobion avenae on some spring wheat cultivars indicated that their numbers were higher at the early growth stages of the awnless cultivar Alexandria than on the awned cultivar Wembley. The distribution of aphids on different parts of wheat plants differed significantly between cultivar types. The fall-off rates of the grain aphids from the awned cultivars was also significantly higher than that on the awnless cultivars. These fall-off rates increased in the same cultivar when the awns were cut.

Natural enemies of the grain aphid (e.g. predators and parasitoids) exerted an important influence in reducing aphid populations in both the laboratory and field experiments. The presence of Coccinella septempunctata and P.melanarius reduced the grain aphid population on different cultivars of wheat.

University of Southampton
Bhuiyan, Md. Serajul Islam
Bhuiyan, Md. Serajul Islam

Bhuiyan, Md. Serajul Islam (1994) Tri-tropic-level interactions between herbivorous insects and their natural enemies. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The ultimate objective of crop protection is to achieve high yield. To do so many control measures, including the application of harmful pesticides are used to combat pest problems, but in most cases the role of the plant itself (first trophic level), and that of the parasitoids and predators (third trophic level) are ignored. Natural enemies have a tremendous influence on herbivores (second trophic level). In this project the role of each of these trophic levels was evaluated. Prior mechanical damage to the leaves of tomato (Lycopersicon esculentum) and oilseed rape (Brassica napus) deterred herbivore (Spodoptera littoralis) feeding and affected the distribution of grazing damage between upper and lower leaves of the plants. The percentage leaf area eaten by the larvae of S.littoralis in the wounded leaves of tomato and oilseed rape in the presence of the soil-dwelling insect predator (Pterostichus melanarius) was significantly lower than that of the unwounded leaves in the absence of predators.

Rearing of the grain aphid Sitobion avenae on some spring wheat cultivars indicated that their numbers were higher at the early growth stages of the awnless cultivar Alexandria than on the awned cultivar Wembley. The distribution of aphids on different parts of wheat plants differed significantly between cultivar types. The fall-off rates of the grain aphids from the awned cultivars was also significantly higher than that on the awnless cultivars. These fall-off rates increased in the same cultivar when the awns were cut.

Natural enemies of the grain aphid (e.g. predators and parasitoids) exerted an important influence in reducing aphid populations in both the laboratory and field experiments. The presence of Coccinella septempunctata and P.melanarius reduced the grain aphid population on different cultivars of wheat.

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Published date: 1994

Identifiers

Local EPrints ID: 458387
URI: http://eprints.soton.ac.uk/id/eprint/458387
PURE UUID: afdc8c2d-91e0-4a15-9402-166857b9fe3a

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Date deposited: 04 Jul 2022 16:48
Last modified: 04 Jul 2022 16:48

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Contributors

Author: Md. Serajul Islam Bhuiyan

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