2 research outputs found
Influence of Temperature and Humidity on the Efficacy of Spinosad Against Four Stored-Grain Beetle Species
In the present work, we examined the insecticidal effect of spinosad, against adults of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) on wheat and the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) on maize. The dose rates used were 0.01, 0.1, 0.5 and 1 ppm. The bioassays were carried out at three temperatures, 20, 25 and 30°C and two relative humidity levels, 55 and 75%. Mortality of R. dominica and S. oryzae was high even at 0.01 ppm of spinosad, reaching 100% at 55% relative humidity and 30° after 21 days of exposure. Generally, mortality of R. dominica, increased with temperature while for S. oryzae mortality increased with temperature and with the decrease of relative humidity. Moreover, for S. oryzae, mortality was low at 20°C. In the case of T. confusum, mortality was low at doses between 0.01 and 0.5 ppm even after 21 days of exposure. At 1 ppm, mortality exceeded 90% only at 30°C and only after 21 days of exposure. Mortality of P. truncatus was low on maize treated with 0.01 ppm, but increasing the dose to 0.1 ppm resulted in > 87% mortality after 14 days of exposure. In several combinations tested, spinosad efficacy notably varied according to the temperature and humidity regimes. Of the species tested, R. dominica and P. truncatus were very susceptible to spinosad, followed by S. oryzae, while T. confusum was the least susceptible
Effect of temperature and humidity on insecticidal effect of SilicoSec against Ephestia kuehniella (Lepidoptera : Pyralidae) larvae
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