A juvenile hormone analogue JHA, SB-515 (Isopropyl (2E, 4E)-11-methoxy-3,7,11 trimethyl-2-1,4-dodecadienoate) was administered to the popular and high yielding bivoltine silkworm hybrid CSR2xCSR4 and its reciprocal cross for enhancing the cocoon yield. The compound was administered at 24, 48 and 72 h of 5th instar at concentrations such as 1.25, 2.5 and 5 ppm as a single dose. Untreated controls were maintained in parallel to compare the results. Apart from measuring the major commercial traits pertaining to cocoon yield, larval growth pattern was studied. The JHA extended the larval feeding period in the range of 6-48 h depending on the concentration of the compound and the time of administration. SB-515 improved the cocoon traits such as cocoon weight, shell weight and cocoon shell percentage significantly. Maximum increase in the case of CSR2xCSR4 was observed in the larvae treated with 2.5 ppm at 48 h whereas, in CSR4xCSR2 this was in the larvae treated at 72 h with the same concentration. Since the enhancement in the cocoon yield is substantial on JHA administration the compound can be exploited in the commercial sericulture.
K.S. Nair, N. Gopal and S.N. Kumar, 2012. Improvement in Cocoon Yield Induced by a Juvenile Hormone Analogue, SB-515 in the Bivoltine Silkworm (Bombyx mori L.) Hybrid, CSR2 x CSR4 and its Reciprocal Combination. Journal of Entomology, 9: 50-56.