Exploitation of Eri – Mulberry Silkworm Degumming Solution for Cultivation of Entomopathogenic Bacteria and Its Efficiency to Control Beet Armyworm

Abstract

The degumming waste water of eri and mulberry silkworm was studied on the exploitation by using as a medium for cultivation of a major bacteria as an insect biopesticide, Bacillus thuringiensis var. kurstaki (Btk) and B. thuringiensis var. israelensis (Bti). Distilled water
and sodium carbonate (Na₂CO₃) solution were used as degumming treatment. Degumming water using distilled water or Na₂CO₃ solution was mixed with nutrient broth (NB) or direct use as the cultured media. The result showed that in case of using distilled water and comparing to NB, the Btk and Bti grew the best on NB (2.95×10⁹ and 1.18×10⁹ cfu/ml), respectively. The subordinate
treatment for Btk was NB + eri degumming water (EDW) + mulberry degumming water (MDW) (2.63×10⁹ cfu/ml), which was not significantly different to NB. However, for Bti the following treatment was NB + EDW (7.88×10⁸ cfu/ml) but was statistically significant (P<0.05) to NB. On the other hand, using Na₂CO₃ as degumming solution, the Btk and Bti grew the best in NB + eri degumming Na₂CO₃ solution (EDS) + mulberry degumming Na₂CO₃ solution (MDS), which exhibited bacterial cells of 4.94×10⁹ and 4.04×10⁹ cfu/ml, respectively. The Btk obtained from cultivation with different media were tested in laboratory on the efficiency to control beet armyworm (Spodoptera exigua). It was revealed that the infected mortality of S. exigua was 90.00, 63.33, 56.67 and 56.67% from NB, EDS, EDW and MDS, respectively.