Thirty bacterial isolates were isolated from the gut contents of diseased/dead locust. Their pathogenicity was tested against 4th instar nymphs of desert locust, Schistocerca gregaria Forskål (Orthoptera: Acrididae). Two isolates, designated DL2 and DL6, out of thirty showed the highest insecticidal activities against locust nymphs in preliminary bracketing. They were bioassayed via leaf dip and per os techniques and toxicity was determined using SAS program. The insecticidal activity of DL6 was more than DL2, whereas LC 50 's values of 35 × 10 6 and 13 × 10 6 cfu's/ml were determined for DL2 and DL6, respectively, after 48 h of leaf-dip treatment. However, LD 50 's value of 53 × 10 6 and 26 × 10 6 cfu's/ml was determined for DL2 and DL6, respectively, after 24 h of per os treatment. The relative potencies of DL6 to DL2 were (2.6 and 2.03) folds in leaf-dip and per os treatments, respectively. Biochemical characterization was conducted, using GEN III MicroPlate™ Biolog identification system and confirmed with molecular identification via 16S rDNA gene sequencing. Nucleotide sequencing of each was submitted to a gene bank and an accession number was generated for each isolate. Obtained bacterial strains DL2 and DL6 were identified as Bacillus weihenstephanensis (KY630645) and Pseudomonas sp. (KY630649), with a similarity of 100 and 75% to B. weihenstephanensis strain PHCDB9 (NR_024697) and Pseudomonas sp. strain DSM11821 (KF417541), respectively. The tested strains proved their potential to be bio-pesticide agents involved in controlling desert locust nymphs.

Thirty bacterial strains were successfully isolated from dead/diseased nymphs of the desert locust Schistocerca gregaria Forskal (Orthoptera: Acrididae) occurred in rearing cages at Egypt. Among them, two isolates, DL3 and DL4, showed a high biocidal activity against locust at preliminary bracketing bioassay. Molecular identification of the two bacterial isolates was carried out by sequencing the 16S rRNA gene and nucleotide blast of international GenBank, and the results showed that DL3 isolate was Bacillus cereus (KY630646) and DL4 isolate was Bacillus cereus (KY630647) with a 100% similarity with Bacillus cereus strain SZAN-2 (GU222440) and Bacillus cereus strain KPRR3 (KY556439), respectively. The insecticidal activity of both isolates against locust nymphs using leaf dipping and per os techniques proved that DL4 isolate was more efficient than DL3 and both of them have the potential to be successful biocidal agents to control desert locust.

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Examination was done at preliminary bracketing bioassay on one old 4 th nymphal instar of desert locust. Results showed that two isolates, namely NDL1 and NDL2 were having highly potentiality as entomopathogenic bioagents. Thirty isolates were isolated from dead/ infected nymphs of desert locust occurred in raring cages at Depart-