Some responses of cabbage root fly (Delia brassicae) to ally I isothiocyanate and other volatile constituents of crucifers

Abstract

SUMMARYVapour components emanating from disrupted cauliflower, turnip, radish, wallflower and brown mustard tissue were assessed for their effects on the cabbage root fly (Delia brassicae). Of about 20 vapour components detected and separated by gas chromatography, six elicited sufficiently large electroantennal responses to warrant further testing, but of these only allyl isothiocyanate and hexyl acetate markedly affected the behaviour of gravid flies in an olfactometer. In wind‐tunnel tests at a wind speed of 1–2‐1‐7 m/s, the numbers of females caught was increased when allyl isothiocyanate vapour was released at 32–130 mg/h but decreased at higher evaporation rates. The only effect of hexyl acetate vapour released at 40–140 mg/h was a reduction in the numbers caught at the highest concentration.In a cabbage crop, yellow water traps fitted with allyl isothiocyanate sources, each evaporating 2–3 g/day, caught 11 times as many female and seven times as many male flies as unmodified traps during the early period of the third generation but the improvement in trap efficiency later diminished. Trap efficiency was slightly reduced when the rate of evaporation of allyl isothiocyanate from a trap was decreased from 2–3 to 0–51 g/day. On fallow ground, allyl isothiocyanate improved trap performance in catching female flies by about seven‐fold, but along a hedgerow adjacent to Brussels sprouts the improvement was barely two‐fold. Hexyl acetate did not improve the performance of traps in a cabbage crop.

The potential of flower odours for use in population monitoring of Western flower thripsFrankliniella occidentalisPerg. (Thysanoptera: Thripidae)

“…Alternatively, the higher concentrations used may have been repellent to F. occidentalis. Odour attractiveness usually shows a concentration-dependent optimum above which compounds that usually attract insects exert repellency (Soni & Finch, 1979;Wallbank & Wheatley, 1979). This may explain why only one of the concentrations used on Chrysanthemum was attractive and not the lower nor the higher ones.…”

Discrimination by the Potato Leafhopper (Hemiptera: Cicadellidae) of Host Volatiles from Resistant and Susceptible Alfalfa,Medicago sativaL.

“…Increased preference of leafhoppers for the solvent control over 1-octen-3-ol and (Z)-3-hexenyl acetate may be caused by a concentration effect. Olfactory orientation can be disrupted if a volatile component is too concentrated, resulting in compounds that normally act as attractants becoming repellents (Visser and Avé 1978, Soni and Finch 1979, Wallbank and Wheatley 1979, Visser 1986). …”

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.…”