|Authors: ||J. Pumnuan, T. Sannongmueang, T. Inyod, A. Insung|
|Keywords: ||oral toxicity, inhibiting growth, anti-feedant, leaf dipping method|
Diamondback moth (DBM), Plutella xylostella is the major insect pest of cruciferous vegetables in Thailand.
When chemicals are wildly used to control this insect pest, it results in an impact on farmer, consumers, environment, and also induces insecticide resistance.
The application of plant extracts is an alternatively effective method to fulfill IPM program.
This study aimed to evaluate the effects of different extracts from leaves and ripe fruit of bastard oleaster (Elaeagnus latifolia), a wild edible plant in Thailand, as water extracts by decoction method, ethanol and hexane extracts by percolation and Soxhlet methods against larvae of DBM. The experiment of insecticidal properties; killing activity, inhibiting growth and anti-feedant by oral test, were investigated on third instar larvae.
The leaf dipping method by using various concentrations of extracts, 0.0 (5% tween-20 in water), 1, 2, 3, 4 and 5% (w/v) was applied, and then compared with fipronil, prothiofos, deltamethrin and abamectin insecticides.
The larval mortality was checked at 24 and 48 h, where the percentages of anti-feedant activity were observed at 24 h.
The surviving larvae are feeded with the treated remains until they develop to the mature and adult stages.
The result showed that ethanol extract from leave of bastard oleaster by percolation and Soxhlet methods were highly effective in killing the larvae of DBM with the LC50 at 24 and 48 h for 4.94-5.47% and 3.42-3.63%, respectively.
Both extracts also showed moderate effectiveness in anti-feedant with >45.0% within 24 h.
Ethanol extracts from leave and fruit by percolation and Soxhlet methods presented the best inhibiting growth of DBM when the concentration at 5% caused 67-87% adult mortality.
Whereas, all selected insecticides tended to be low toxic to this insect with no difference compared to the ethanol extract of bastard oleaster leave.
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