Insecticidal effect of diatomaceous earth, powder and extract of princess tree (Paulownia tomentosa) against lesser grain borer (Rhyzopertha dominica)

Provedeno je istraživanje insekticidnog utjecaja dijatomejske zemlje, prašiva i ekstrakta carske paulovnije na žitnog kukuljičara. Primjenjeni su u tretmanima prašiva lista carske paulovnije, dijatomejska zemlja Celatom Mn-51® i SilicoSec®, te ekstrakti u različitim dozama nakon 7. i 14. dana ekspozicije. Od ekstrakata je korišten: vodeni ekstrakt carske paulovnije; kombinacija vodenog i alkoholnog ekstrakta carske paulovnije pri omjeru 1:1; te alkoholni ekstrakt (2-propanol) carske paulovnije. Insekticidna učinkovitost je ovisila o dozi i ekspoziciji. Najlošije se pokazalo prašivo carske paulovnije koje nakon 7. dana ekspozicije nije postiglo mortalitet. Dijatomejska zemlja (DZ) se pokazala najvišu insekticidnu učinkovitost. Povećanjem doze se i mortalitet povećavao te je najviša doza od 750 mg kg-1 postigla najviši mortalitet. DZ SilicoSec® je postigla viši mortalitet u odnosu na Celatom MN-51®. Od ekstrakata lista carske paulovnije najbolje je djelovao ekstrakt 3 (alkoholni ekstrakt), zatim kombinacija alkoholnog i vodenog ekstrakta carske paulovnije (ekstrakt 2), dok je najniži mortalitet postigao vodeni ekstrakt (ekstrakt 1) carske paulovnije.This research was conducted with the aim to test the insecticidal efficacy of diatomaceous earth, powder and extract of empress tree against lesser grain borer. Treatments with leaf powder of empress tree, diatomaceous earths Celatom Mn-51® and SilicoSec®, as well as extracts in different doses were applied in two different exposures (7 and 14 days). The following extracts were used: aqueous extract; combination of aqueous and alcoholic extract in 1:1 ratio; and alcoholic extract (2-propanol) of the empress tree. The insecticidal influence depended on the dose and exposure. The least effective was the powder of empress tree which on the seventh day of exposure has not achieved any mortality. Diatomaceous earth proved to have the highest insecticidal properties. As the doses were raised the mortality rate was higer. The highest dose (750 mg kg-1) achieved the highest mortality. Diatomaceous earth SilicoSec® achieved a higher mortality rate than Celatom Mn-51®. The most effective extract has proved to be extract 3 (alcoholic extract), followed by the combination of alcoholic and aqueous extract of (extract 2), while the lowest mortality rate was achieved by the aqueous extract (extract 1) of empress tree