Efficacy of some plant oils against two stored product insects

Abstract EN

To investigate the insecticidal activity of marjoram, caraway and worm wood oils against the adults of Sitophilus oryzae (L.) (Curculionidae, Coleoptera) and the active and diapausing larvae of khapera beetle Trogoderema granarium (Everts) laboratory bioassay tests were conducted, at four to five concentrations of each plant oil, of 21days under 30 and 20 ±1°C.

The results indicated that the mortality of tested insects increased with increasing the plant oil concentration, exposure period and temperature, where the complete mortality of S.

oryzae adults was obtained at 1.5 and 1% (v/w) of the three tested oils, after 21 days exposure periods at 30°C.

Data also revealed that at 20°C, the worm wood oil was the most toxic for the studied insects, and it gave LC50s of 2.41, 2.90 and 0.21% for active and diapausing larvae of T.

granarium (after 14 days exposure period) and for the adults of S.

oryzae (after 3 days exposure period), respectively.

Caraway oil was the most toxic at 30ºC against the active and diapausing larvae of T.

granarium.

The adults of S.

oryzae were more sensitive to investigated plant oils than active and diapausing larvae of T granarium.

It can be concluded that marjoram, caraway and worm wood oils have a toxic activity against the two stored-product insects, S.

oryzae and T.

granarium.