The grasshopper Euprepocnemis plorans plorans caused a considerable damage to crops of the Nile Delta, Egypt. The present study was conducted aiming to assess the insecticidal and anti-hormonal effects of Precocene II on this grasshopper. The newly moulted 2 nd or 4 th (penultimate) instar nymphs were exposed to a series of doses: 60, 40, 20 and 10 µg/cm 2. Exposure of 2 nd instar nymphs to the higher two doses resulted in complete mortality of nymphs within 24 h. At the lower two doses, PII exhibited a considerably extended low toxicity on the subsequently moulted instars and emerged adults. LD50 was calculated as 0.388 µg/cm 2. After exposure of the 4 th instar nymphs to PII, no complete mortality was observed, but various mortality percentages among the treated nymphs, 5 th instar nymphs and adults. LD50 was calculated as 17.022 µg/cm 2. PII exerted a slight inhibitory action on the nymphal growth of both 4 th and 5 th instars, after treatment of 2 nd instar nymphs, regardless the dose level, but the growth rate was remarkably regressed after treatment of 4 th instar nymphs with 40 and 20 µg/cm 2. Exposure of 2 nd instar nymphs to PII led to 3.33% precociously moulted nymphs into 4 th instar, skipping off the 3 rd instar (only at the lowest dose). After exposure of 4 th instar nymphs to PII, some treated nymphs precociously metamorphosed into adultoids, omitting the 5 th instar, only at the higher tow doses. Another noticeable feature of the deranged development was 'permanent nymphs' which induced in 2 nd instar nymphs (3.85%) after exposure only to 20 µg/cm 2. Also, similar permanent nymphs were induced during the 4 th instar. No permanent nymphs had been induced after exposure of 4 th instar nymphs to PII.
The objective of the current investigation was to assess the food deterrence property of chromafenozide and its impact on different food metabolic parameters of the 5 th instar nymphs of the desert locust Schistocerca gregaria. For this purpose, three doses (10, 100 and 150 µg/nymph) were topically applied (once) onto the newly molted last (5 th ) instar nymphs. chromafenozide exhibited contradictory effects on the feeding since it acted as a weak antifeedant against female nymphs only at the lowest dose but acted as phagostimulant against their congeners at the higher two doses. Furthermore, the compound exerted a general phagostimulant action on the male nymphs, regardless the dose. The food intake by the last nymphal instar females was slightly reduced only at only the lowest dose but remarkably increased at the higher doses. The male nymphs had been promoted to consume more food amount. Treated nymphs of both sexes attained slightly or significantly increasing relative weight gain and discharged more frass pellets. The treated nymphs of both sexes achieved slightly increasing approximate digestibility (AD), with two exceptions for the male nymphs which had a slightly decreased AD at the medium dose and unaffected AD at the highest dose. Both the efficiency of conversion of ingested food into biomass (ECI) and efficiency of conversion of digested food into biomass (ECD) of the female nymphs slightly increased. ECI of male nymphs was enhanced but ECD was slightly inhibited. Depending on the present results, Chromafenozide cannot be recommended as a promising agent for controlling S. gregaria.
http://eajbsa.journals.ekb.eg/ Disturbance of the Acetylcholinesterase Activity in Haemolymph and Fat Bodies of The Desert Locust, Schistocerca gregaria (Orthoptera: Acrididae) by Margosan-O ® (0.3% Azadirachtin)
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