Insecticidal Effect of Pătârlagele Diatomaceous Earth Against Acanthoscelides Obtectus Adults

In the present study there are presented the results obtained in laboratory tests to evaluate the efficacy of the Romanian diatomaceous earth from Pătârlagele deposit in Buzău County (DE PatRom) against adults of three population of the bean weevil Acanthoscelides obtectus L. (one maintained in laboratory conditions at the Plant Protection Institute Bucharest and the others two came from fields bean from Buzău and Bacău) compared with two commercial formulations (SilicoSec® and PyriSec® ). The DE PatRom was applied at four doses 100, 300, 500 and 900 ppm while SilicoSec® and PyriSec® at the doses registered in common practice. Tests were carried out at 25±2°C and at 70± 5% relative humidity (RH). Adult mortality was assessed 3, 7 and 14 days after treatment. The PyriSec DE was the most effective reaching a total mortality of adults for all three insect populations tested even after 3 days, followed by SilicoSec DE which caused mortality between 74 and 99% after 3 days and 100% after 7 days. The mortality levels of A. obtectus adults reached by Romanian DE PatRom varied depending on dose, period after treatment and insect population. The mortality of bean weevil increased with increasing dose and period after treatment. The highest mortality (of 93, 96 and 98.5% to adults in Buzău, Bucharest and Bacău population, respectively) was recorded in bean treated with 900 ppm after 7 days. The results in experiments showed that the A. obtectus adults of Bacău population were more susceptible and those of Buzău population were more tolerant to all DEs tested.