Time, concentration and temperature relationships for phosphine activity in tests on diapausing larvae ofEphestia elutella(Hübner) (Lepidoptera: Pyralidae)

摘要

AbstractThe activity of phosphine against diapausing larvae ofEphestia elutellawas shown to depend on several different interactions of duration of exposure, temperature and gas concentration. Using the model proposed by Knight, (CC0) × (tt0) = k, a constant for mortality, the minimum effective concentration C0was raised and the minimum effective exposure t0extended as temperatures were increased. The effect of temperature on these thresholds was reduced at higher mortality levels. A range of concentration levels, influenced by temperature, elicited an increase in tolerance at the LD99level over that evident at higher or lower concentrations. These concentration ranges were 0.9–2‐1 mg litre‐1at 25°C,0.7–2.3 mg litre‐1at 20°C and 0.1–1.5 mg litre‐1at 15°C.A mathematical model was fitted to relate concentration and time thresholds, mortality and temperature. At the LD50level, values for t0ranged from 2.5 h at 15°C to 5.0 h at 25°C. C0values increased from about 0.6 to 7.0 μg litre‐1over this temperature range. At the LD99level, t0values ranged from 21 to 28 h and C0values from 11 to 19 μg litre‐1. Phosphine appeared most effective at each temperature at concentrations from