Potential of some chemicals to increase the effectiveness of Bacillus thuringiensis Berl. against Spodoptera littoralis (Boisd.)

Abstract

Biochemical approaches have been adopted to increase the potency of Bacillus thuringiensis var. entomocidus against the cotton leafworm Spodoptera littoralis. Chemicals of various groups were assessed with respect to their effect in increasing the potency of the endotoxin. Results indicate that some lipid emulsifying agents, protein solubilizing agents, and some of the non‐toxic nitrogenous compounds tested increased the potency of the endotoxin in varying degrees (2.7–21.7 fold increase). Sodium benzoate as a representative of aromatic compounds also enhanced the endotoxin potency (2.5 fold increase), while the chelating agent EDTA had an antagonistic effect. Calcium, zinc, and copper salts remarkably potentiated the effectiveness of the endotoxin; the factors of increase were 24 and 19 as shown with zinc sulphate and calcium oxide salts. In the light of the results obtained, the mode of action of these chemicals has been discussed. So, B. thuringiensis may perform with high potency at lower concentrations if it is combined with some of these active and low cost chemicals and thus adding to the feasibilities of use. Zusammenfassung Möglichkeiten zur Steigerung der Wirkung von Bacillus thuringiensis Berl. gegenüber Spodoptera littoralis (Boisd.) mit Hilfe einiger Chemikalien Es wurden biochemische Versuche unternommen, um die Wirkung von B. thuringiensis var. entomocidus gegen die Raupen der Baumwolleule, S. littoralis, zu erhöhen. Dabei wurden chemische Verbindungen verschiedener Gruppen im Hinblick auf eine Steigerung der Endotoxin‐Wirkung betrachtet. Die Ergebnisse zeigen, daß einige Fett‐emulgierende und Protein‐lösende Substanzen sowie einige nicht‐giftige Stickstoffverbindungen die Endotoxin‐Wirkung in verschiedenem Maße (2,7‐21,7fache Steigerung) erhöhten. Auch Natriumbenzoat als eine repräsentative aromatische Verbindung führte zur Wirkungssteigerung (2,5fach). Dagegen zeigte der Chelatbildner EDTA einen antagonistischen Effekt. Kalzium‐, Zink‐ und Kupfersalze vergrößerten die Wirksamkeit des Endotoxins erheblich (Zinksulfat 24fach, Kalziumoxyd 19fach). Im Lichte dieser Ergebnisse wird der Wirkungsmechanismus der getesteten Chemikalien erörtert. Demnach könnte B. thuringiensis bei niedrigerer Konzentration eine höhere Wirkung erlangen, wenn es mit einem dieser aktiven, billigen und unschädlichen chemischen Verbindungen kombiniert wird.

Evaluation of alternativePlutella xylostellacontrol by twoIsaria fumosoroseaconidial formulations - oil-based formulation and wettable powder - combined withBacillus thuringiensis

“…Morris et al . and Salama et al . reported that surfactants could enhance the insecticidal activity of B. Thuringiensis .…”

“…reported that surfactants could enhance the insecticidal activity of B. Thuringiensis . Salama et al . hypothesised that surfactants disrupt the insect gut epithelium, increasing permeability to bacterial toxins.…”

“…Burges 68 demonstrated that formulation ingredients widely used in modern biopesticide formulations may synergise the activity of entomopathogenic fungi. Morris et al 69 and Salama et al 70 reported that surfactants could enhance the insecticidal activity of B. Thuringiensis. Salama et al 70 hypothesised that surfactants disrupt the insect gut epithelium, increasing permeability to bacterial toxins.…”

Repellent and Insecticidal Activities of Melia azedarach L. against Cotton Leafworm, Spodoptera littoralis (Boisd.)

“…The Egyptian cotton leafworm S. littoralis is considered as the major pest in a wide range of cultivation including cotton, corn, soybeans, peanuts, and vegetables. This pest is not only widely spread in Egypt but also in other Middle East countries in addition to temperate zones in Asia and Africa (Salama et al, 1990).…”

Disruptive Effects of Some Novel Chitin Synthesis Inhibitors on the Transaminase Activity in Larval Tissues of Spodoptera littoralis (Lepidoptera: Noctuidae)

“…It is a serious or major pest of cultivated crops primarily in tropical and subtropical regions, in Africa, Southern Europe, Middle East and Asia Minor [83] and the Mediterranean area [84][85][86][87][88][89]. Objective of the present study was to investigate the effects of novel CSIs, viz.…”