Co-Authors:
Navon, A.
Wysoki, M.
Keren, S., Div. of Entomology, ARO, The Volcani Center, Bet Dagan, Israel
Abstract:
The potency of two new Bacillus thuringiensis (B.t.) preparations (coded ABG 6104 and ABG 6105) and of Dipel (B. thuringiensis var. kurstaki) was determined against Spodoptera littoralis (Boisd.) 5th-instar larvae on a calcium-alginate diet. With this bioassay, the new B.t. products were more than twice as potent as Dipel. They were also 2-3 times more active than Dipel on alfalfa and cotton leaves in the laboratory. When applied in an alfalfa field at the rate of 312 mg/m2, ABG 6104 and ABG 6105 caused 40% mortality of 5th-instar larvae and reduced the weight of the survivors to 30-40% of the control; only half of this activity was obtained with Dipel. On cotton, the activity of all the B. t. products was low. Neonate S. littoralis larvae were effectively controlled on avocado seedlings; however, there was high mortality also in the untreated controls. All three B. t. preparations had a similar effect on Boarmia (Ascotis) selenaria Schiff. on avocado leaves in the laboratory. Addition of a chitinase enzyme did not increase the pathogenicity of the microbial preparations in the latter tests. © 1983 Springer Science + Business Media B.V.