SINIGRIN AS A FEEDING DETERRENT IN 2 CRUCIFER-FEEDING, POLYPHAGOUS LEPIDOPTEROUS SPECIES AND THE EFFECTS OF FEEDING STIMULANT MIXTURES ON DETERRENCY

The glucosinolate, sinigrin (allyl- or 2-propenyl glucosinolate), pres ent in several Cruciferae, was incorporated in varying concentrations into four different diet background mixtures to study the behavioural reactions of Mamestra configurata and Trichoplusia ni. Sinigrin concen trations were chosen to mimic normal levels in naturally occurring cru ciferous plants, or to represent a plant during a particular stage in its growth cycle. One diet background mixture contained potassium chlo ride (KCl) and no stimulatory sugar or sugar alcohol, two backgrounds contained KCl and a single sugar or sugar alcohol (sucrose or inositol , respectively), and the fourth background contained KCl and both suga r and sugar alcohol (sucrose and inositol, respectively). Sinigrin act ed primarily to reduce (deter) feeding in all backgrounds, although th e effect varied with sinigrin concentration, background and species. W hen inositol or sucrose was included in the mixture, the deterrent eff ect of sinigrin was decreased in both species. When inositol and sucro se were present, suppression of the deterrent effect of sinigrin was g reatest for M. configurata. The effects of mixtures were not predictab le from a knowledge of the action of individual components. Difference s observed between species may reflect different sensory capabilities.