The black-kneed capsid bug, Blepharidopterus angulatus(Fallen) is an important colonizer of orchards in late summer. Capsids develop on alder windbreaks feeding on the aphid Pterocallis alni(Degeer). When the aphid population declines adult bugs move to nearby orchards where they feed on pest species. The biology and ecology of P. alni has been examined in order that predator populations may be manipulated. Aphid populations increase rapidly to a peak, then suddenly decline. A high initial population results in a peak in mid July, low initial numbers result in a peak in early August. Pruning of the windbreaks can alter the population cycles of the aphid. P. alni is polymorphic and crowding results in the production of winged individuals. The crowding stimulus acts pre and post natally. Flight is stimulated by crowding and emigrating alatae colonize other alder trees. Sexual forms of the aphid are produced as a response to a shortening of the daylength in autumn. In field conditions adult aphids produce a reproductive sequence of virginoparae, males and finally oviparae. Egg laying and distribution were examined and winter mortality monitored. Arthropod predators are the main cause of egg loss and greatest mortality occurs in early winter. The food quality of alder leaves for the aphids deteriorates in early summer. Poorer food, rising temperatures and increased crowding result in smaller aphids which are less fecund. Recruitment to the population falls and numbers collapse when emigration exceeds recruitment. The emigration of B. angulatus from alder is closely synchronized with the abundance of P. alni. The key mortality factor in bug populations is theloss of reproductive females. However, female capsids tend to remain on the windbreak unless their prey disappears completely. If this occurs, both sexes will migrate to the orchard. Capsid numbers and movements are indirectly affected by cultural practices of the alder resulting-in changes in aphid abundance
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:540759 |
| Date | January 1985 |
| Creators | Gange, Alan Christopher |
| Publisher | King's College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://kclpure.kcl.ac.uk/portal/en/theses/the-ecology-of-the-alder-aphid-pterocallis-alni-degeer-and-its-role-in-integrated-orchard-pest-management(20ddfb21-20f5-48d9-8e0e-db9d338a182b).html |
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