VOLATILE PLANT CHEMICALS AND THEIR EFFECT ON HOST PLANT FINDING BY THE CABBAGE ROOT FLY (DELIA BRASSICAE)

Abstract

Volatile plant chemicals are generally credited with a major role in host plant location by many phytophagous insects. Mixtures of volatiles are produced in cruciferous plants mainly by the hydrolysis of non-volatile glucosinolates to volatile isothiocyanates, thiocyanates and nitriles. The cabbage root fly attacks a wide range of cruciferous plants, with differing odours, implying that several volatile chemicals are probably involved in attracting the flies and in stimulating them to lay. Oviposition by the cabbage root fly was studied, therefore, on a large range of wild and cultivated plants to determine the most preferred species. The volatile chemicals in these species were identified in the hope that some of them may prove more useful as attractants for luring cabbage root flies to field traps. Similar volatile chemicals were released from both intact and macerated plants. It was deduced that any one, or combinations, of eleven chemicals may probably be involved in attraction and host plant selection by this fly. The concentrations of these chemicals change during the life of the plant, however, and an initially attractive chemical can become so concentrated that eventually it repels the insect. Difficulties encountered in experiments on olfaction and possible ways in which they can be overcome are discussed. This paper describes how certain host plant chemicals affect cabbage root fly, Delia brassicae (Wiedemann), behaviour and how they can be used in traps either to monitor or reduce populations of this pest. The cabbage root fly was chosen for the initial study because it can be mass-reared easily in the laboratory (Finch & Coaker, 1969), because its peak of activity can be readily determined in the field, and because its larvae damage the roots of crucifers throughout much of the northern hemisphere, including the whole of the British Isles. This root damage prevents uptake of water and nutrients causing the plants to wilt and, in severe infestations, to die. Methods of host erop findingAgronomic practices associated with vegetable production create large ecological disturbances and the insects that become pests of vegetables are usually well adapted to such disturbances (Southwood, 1962). They tend to be highly mobile and so are capable of finding easily new host crop plantings. Host-finding appears to depend in part on the insect reacting to characteristic chemical odours produced by their host plants.

Spatial distribution of cabbage root maggot (Delia radicum) and clubroot (Plasmodiophora brassicae) in winter oilseed rape crops in the Czech Republic

“…According to Dosdall et al (1995) (Traynier 1967;Finch 1978;Hawkes & Coaker 1979;Nottingham 1988). The role of visual stimuli is also very important, especially in the phase before landing (Prokopy et al 1983;Košťál 1991).…”

Development of bisexual attractants for diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae) based on sex pheromone and host volatiles

“…The composition of volatiles found in cabbage plants consists of fatty acid derivatives, terpenoids, benzenoids and a few sulfur-containing compounds, such as methyl isothiocyanate (Finch, 1978;Visser et al, 1979;Tollsten and Bergström, 1988;Reddy and Guerrero, 2004). In this study, the electrophysiological responses of DBM males and females to volatile components from Brassicaceae were tested in the laboratory.…”

The processing of a complex food odor by antennal olfactory receptors ofPeriplaneta ameriana

“…In behavioral experiments mixtures of odor components as well as single compounds were shown to be the attractive constituents of some foodstuffs (Werner 1972;Visser and Av6 1978;Finch 1978;Saxena and Goya 1978;Hardman and Ellis 1978;Wallbank and Wheatley 1979). In electrophysiological investigations mainly chemically purified constituents of foodstuffs were demonstrated to be effective stimuli, but no attempt was made to apply them in their natural concentrations (Mustaparta 1975;van der Pets 1978;Den Otter etal.…”