Feasibility of polylactic acid and essential oil composite with insecticidal properties for prevention of Sitophilus oryzae and Oryzophilus surinamensis in Sorghum and Pearl millet.

Current study provides insight on the feasibility of polylactic acid (PLA) integrated with (1:1 ratio) of essential
oils belonging to Ocimum gratissimum (OG) and Mentha spicata (MS) for prevention of major stored insect pests
(Sitophilus oryzae and Oryzophilus surinamensis) in Sorghum and Pearl millet. A combination of OG and MS essential
oils (1:1) was incorporated into the PLA polymer matrix. Further, SPME analysis of synthesized PLA showed the
presence of volatiles corresponding to carvone (6.44 %) and thymol (6.22 %). Synthesized PLA composites were
tested against S. oryzae and O. surinamensis using Sorghum and Pearl millets, and insect mortality was equivalent
to commercial super bags (CSB). The head space oxygen decreased significantly in CSB and slightly in PLA bags.
Thickness of EO blended PLA composite was increased (99 μm), tensile strength (23.94 MPa), WVTR (1.42 g/m2.
hr) analysis, significant folding ability, and swelling capacity (0.24 %) showed slight reduction in composite film.
TGA showed good thermal stability (334˚C) and XRD displayed the increased crystallinity (38.35 %) in PLAOM
films, SEM and FTIR analysis of the synthesized composite films revealed complete homogenization of EO and
PLA matrix. In addition, SEM analysis of insects (control & treated) revealed less topology changes in the elytra.
Biodegradability study confirmed the weight loss in PLA films. Hence, current approach of using composite EO's
with PLA offers sustainable solution for prevention of infestation during storage of millets.