	SSP 1994 project summary:

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Host Plant Selection by Turnip Root Flies

Turnip root flies are plant feeding insects. The adult fly is highly mobile and oviposits, lays eggs, at the base of host plants, the eggs hatch and the larvae then feed on the roots of the brassica plants concerned. The host selection process is quite complex, the adult lands on the leaf of the potential host plant and then proceeds to examine the surface of the leaf, stem and base of the plant prior to laying eggs if the plant is suitable. If the host plant appears unsuitable at any stage in the host selection process the female fly rejects the plant and flies off to find another plant.

In addition to the suitability of the plant, the physiological status of the fly is of great importance. Throughout their reproductive life, the female flies produce a number of eggs each day. It is an excepted facet of host plant selection that as the period since the fly last oviposited increases, the female fly becomes more likely to lay eggs at any given encounter. Consequently, both the susceptibility of a plant to oviposition and the distribution of plants within an environment influence the extent to which eggs are laid upon them. The applied element of this from a biological viewpoint is that a valuable crop may be protected from an insect pest with a strip of highly susceptible host plants. Eggs are laid in the band of susceptible plants that are then destroyed, killing the pest.

By modelling the behaviour of a series of individuals it may be possible to assess how the relative proporation of resistant and susceptible plants affact the damage sustained by a crop during the course of a growing season.

Deborah Bellotti worked on this project.

Compressed PostScript of Deborah's final report is available here (250051 bytes) .

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