Dual effect of the antibiotic Cycloheximide on desert locust Schistocerca gregaria forskal (Orthoptera: Acrididae)
Muhammad Tanani
The desert locust Schistocerca gregaria is a dangerous pest devastating agricultural productions and pastures in different countries. The objective of the present study was to assess the dual effect of cycloheximide (RNA and protein synthesis inhibitor), JH-like activity and anti-JH activity, against this pest. Five doses (200, 100, 30, 20 and 10 µg/nymph) were topically applied onto the sternites of newly penultimate (4th) instar nymphs S. gregaria in Faculty of Science, Al-Azhar University, Cairo, Egypt.Cycloheximide exhibited a toxic effect on nymphs and adults. LD50 was 8.53 µg/nymph. It exerted a potent suppressing action on nymphal growth and developmental rate. As a symptom of the suspended development, some of the treated 4th instar nymphs failed to moult into the next instar but remained as permanent nymphs and died after 4-fold period of the control nymphs. The successfully moulted 5th instar nymphs suffered an impairing action of cycloheximide; since malformed nymphs were produced and died after a few days. Some of the treated nymphs precociously metamorphosed into adultoids, skipping off the 5th instar. These precocious adultoids spent more than one month and eventually died with mating. In addition, cycloheximide induced solitary tendency in the treated 5th instar nymphs, at the lower two doses.