Abstract
Over the past half century, killing of agricultural pests or insect by synthetic chemical pesticides in the field or post-harvest the crops cause insect resistance and health hazards to man and pollute the environments. There is a great need for developing alternative approaches to control harmful insect pests. Essential oils (EOs) and their nanoemulsions (NEs) have broad insecticidal activity against some bests. This study was conducted to investigate toxicological effects of some EOs and their nanoemulsions on the early life stage (24 hr post-hatch nauplii) of brine shrimp Artemia salina. Oil of four plants (Neem, Eucalyptus, Clove and Basil) were collected and their NEs either alone or mixed with Neem were prepared and characterized. The diameter of the nano- particles were 200.1, 211.9, 218,7 and 288.7 nm for Neem, Clove, Basil and Eucalyptus, respectively. All the particles had negative charge. The average diameters were 266.2, 425.1, and 316.1 for Neem+Clove, Neem +Basil and Neem +Eucalyptus, respectively and all the prepared nanoemulsion particles have negative charge. It was found that increasing concentrations of essential oil increased mortality percentage up to 100 %. Moreover, increasing time increased percentage of mortality. The mortality levels were 100 at concentrations of 24, 20 and 16 % after 24, 48 and 72 hr, respectively. The lethal concentration 50 (LC50) of these oils and NEs on Artemia salina nauplii was determined after 24 hours of exposure The LD50 of the tested neem oil was calculated at 50% mortality level. Similarly, effect of different concentrations of neem oil nanoemulsion on percentage of mortality of Artemia salina nauplii after 24, 48 and 72 hr were determined and compared and increasing concentration of neem oil nanoemulsion increased percentage of mortality and increasing time increased also the percentage of mortality. From the previous results, LD50 doses for neem oil nanoemulsion were 12, 10 and 8 % after 24, 48 and 72 hr. LD50 was calculated after 24 hr for each oil or nanoemulsion prepared from single or mixed oils. LD50 values were ranged from 16-46 % for the tested oil and from 12-41% for nanoemulsion of essential oils. Neem oil showed the greatest activities against the tested larva. In conclusion, essential oils of Neem, Eucalyptus, Clove and Basil, applied singly or mixed with neem and their prepared nanoemulsions have broad insecticidal activity and can be used safely against some insect bests.