The Effect of Mixtures of Bacillus Thuringiensis and Growth Regulators on the Physiological State of the Caterpillars

1991

S. 533-542

9 Lit. Ang.

Unselbständiges Werk

200062015

Lesnictvi 1991 ; 37(7), S. 533-542

Laboratory trials were conducted to test the effect of the promising mixtures of the biopreparation based on Bacillus thuringiensis var. kurstaki with sublethal doses of the growth regulators diflubenzuron and teflubenzuron in the control of the caterpillars of Lymantria dispar. The effect of the different experimental treatments on the viability and physiological state of the caterpillars was evaluated on the basis of determination of the levels of reserve substances in the bodies of the caterpillars after the tests were finished. Under field conditions the tested variants of the preparations were experimentally applied during the aerial control of Tortrix viridana in oak stands. In the laboratory, the strongest effect in the control of L. dispar caterpillars was recorded in the mixture of Bathurin 82 (100g per ha) and Nomolt 15SC (100mg of active ingredient per ha ): the effectiveness of this treatment, compared with that using pure biopreparation, was higher by 37.3% after five days. No such favourable effect was demonstrated in the case of mixture of Bathurin 82 with Dimilin 48SC. As the effectiveness of Bathurin 82 applied at a rate of 100g per hectare was comparatively high, it appears suitable in further tests with combined treatments to reduce the Bathurin 82 dose to 50g per hectare. As demonstrated by the analysis of the caterpillars that had died during the tests, the lipid levels varied greatly and were both higher and lower in the different treatments, compared with the control. an increase in lipid levels was recorded after the application of the growth regulators alone (+12.99%, +9.39% in comparison with control) and after the application of the mixture of Bathurin with Dimilin 48SC (+8.05%). On the other hand, a decline in the content of lipids was recorded after the application of a mixture of Bathurin 82 with Nomolt 15SC. The content of glycogen in the bodies of the caterpillars declined in all variants of treatment (-10.6 to 18.7mg per 1kg, compared with the control). Considering the influence on the viability of the experimental caterpillars, the mixture of Bathurin 82 with Nomolt 15SC had the strongest physiologicial effect: the caterpillars had the lowest level of reserve substances after application of this mixture. Aerial application of the biopreparation Bathurin 82 at rates of 1 and 2kg per ha (16 and 32 BIU) had an effectiveness of 73 and 85% in the control of Tortrix viridana caterpillars. The application of a mixture of Bathurin 82 (1kg per ha) with Dimilin 48SC (3 and 6g of active ingredient of diflubenzuron per ha) had an effectiveness of 90 and 93%, i.e. 17 to 20% more in comparison with the pure biopreparation.