Assessing the role of biodegradable polymer composites in mitigating insect infestations of pearl millet: Focus on polylactic acid and polybutylene adipate terephthalate with phytochemicals

Current study, highlights development of composite mixture of polylactic acid (PLA) and polybutylene adipate
terephthalate (PBAT) incorporated with phytochemicals (thymol, α-pinene, eucalyptol, estragole) as insecticidal
biopolymers. Further, these developed films were analysed with gas chromatography–mass spectrometry
(GC–MS) coupled with solid-phase microextraction (SPME) and results showed the presence of thymol, α-pinene,
eucalyptol, estragole in the composite films (PLA-PBAT-T 0.5 %, PLA-PBAT- A 4.5 %, PLA-PBAT-E 4.5 %). The
synthesized films showed significant mortality (100 %) towards Sitophilus oryzae within 72 h whereas Oryzophilus
surinamensis exhibited complete mortality within 48 h in presence of grain (pearl millet) conditions. Seed
germination study showed seed viability (100 %) in the tested grains which was equivalent to fresh grains.
Mechanical property (tensile strength) was reduced (lowest in PLA-PBAT-AT 5 % - 10.44 MPa), but the water
vapour transmission rate (WVTR) was found to be significant in PLA-PBAT-T 0.5 % blend (13.63 g/m2.hr). The
XRD analysis showed increase in the crystallinity index of PLA-PBAT-T 0.5 % (15.68 %), PLA-PBAT- AT 5 %
(14.75 %) and PLA-PBAT- ET 5 % (13.77 %) films. Fourier transform infrared spectroscopy and scanning electron
microscopy analysis of the biopolymer films showed complete homogenization of the phytochemicals and weight
loss (maximum 4.9 %). Overall, phytochemical amended biopolymer films displayed significant insecticidal
activity in prevention of storage pests of pearl millet.