Laboratory experiments were carried out to assess the insecticidal
effect of the diatomaceous earth formulation SilicoSec against larvae of
Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), in stored wheat
(Triticum durum Desf.). Larvae were exposed to wheat treated with
SilicoSec at 400 and 800 ppm and held at 20, 25, and 30 degrees C and 55
and 75% RH. Larval mortality was assessed after 24 h, 48 h, 7 d, and 14
d of exposure in the treated wheat. At both dose rates, mortality
increased with temperature, but this increase varied with the exposure
interval. At short (<= 48-h) exposures, larval mortality was
significantly higher at 30 degrees C than at the other two temperatures.
In contrast, no significant differences were noted between 20 and 25
degrees C. At longer exposures (>= 7 d), the increase of temperature
increased mortality at 800 ppm, but no significant differences were
noted between 25 and 30 degrees C at 400 ppm. Furthermore, significant
differences in larval mortality were noted between the two humidity
levels, but only at exposures :7 d. After 14 h of exposure, at both dose
rates examined, the increase of temperature significantly decreased
mortality. The results of the current study indicate that E. kuehniella
is susceptible to SilicoSec, but temperature and relative humidity
should be taken into consideration