Individual and combined use of inert and plant dusts against the rice weevil (Sitophilus oryzae) adults on wheat and corn grains

Abstract: Laboratory research was performed to evaluate efficacy of inert dusts and plant
powders against rice weevil (Sitophilus oryzae) adults. Efficacy was performed on two different grain varieties, wheat grain and corn. We have tested the efficacy of zeolites, quartzs sand, wood ashes and diatomaceous earth of Slovenian origin. Product SilicoSec served as positive control. Inert dust was applied at two different concentrations, 450 and 900 ppm, when applied as a single application and 300 ppm, when we have applied mixtures of inert dusts and plant powders. We have used crushed dried leaves of Solidago gigantea and Solidago canadensis as plant powders. Experiment was performed at four different temperatures (15, 20, 25 and 30 °C) and two different relative humidity values (55 and 75 % RH). Mortality was evaluated 7th, 14th and 21st day after exposure. The highest efficacy of treatments was recorded on wheat grain (26 % dead individuals) in comparison to corn, where only 11 % individuals were dead. The highest mortality was detected in treatments, which included product SilicoSec at 450 ppm and 900 ppm (100 % mortality was recorded after 21st of exposure on wheat grain). 50 % of individuals were dead after the 21st day, when diatomaceous earth of Slovenian origin was applied on wheat grain. When plant powders were applied, less than 10 % of individuals were dead. Our study has proven high efficacy of inert dusts, when applied as single products and negligible efficacy of plant powders from invasive species.