Molecular identification, life history description and biotic potential of Plodia interpunctella (Lepidoptera: Pyralidae) feeding on amaranth (Amaranthus sp.) products in the state of Morelos, Mexico

Abstract

The flour moth Plodia interpunctella (Hübner) is considered one of the most significant pests of stored and processed products, its adaptability allowing it to settle on new food hosts. In 2020 in Mexico, the presence of larvae and adults of P. interpunctella in amaranth products stored and processed for export was reported for the first time, causing considerable damage. The objective of this study was molecular identification of the insects found in amaranth products and description of the biotic potential of these pests grown in different amaranth products under laboratory conditions. For this purpose, molecular identification of P. interpunctella was carried out using the mitochondrial gene cytochrome oxidase subunit one (COI). Three cohorts with 200 eggs each, fed with three types of amaranth products (amaranth with chocolate, amaranth with honey and natural amaranth) were implemented, with hatching rates of 75% for amaranth with chocolate, 66.5% for amaranth with honey and 71.5% for natural amaranth. The larval period consisted of five instars and one prepupa, with the shortest life expectancy in the first instar. The life cycle of the insect varied from 51 days in chocolate amaranth, 54 days in honey amaranth and 64 days in natural amaranth. This lepidopteran presented a high fecundity when fed with chocolate amaranth with a mean clutch size of 257.0435.98 eggs per female during her whole life (h/h/v), followed by honey amaranth with 177.3836.23 (h/h/v) and finally by natural amaranth with 157.643.33 (h/h/v), with a mean fertility of 71%. In the population parameters, a generation time (T) of 25.08, 26.69 and 31.41 days and a net reproduction rate (R0) of 405.10, 253.82 and 215.49 were obtained for amaranth with chocolate, with honey and natural respectively, ensuring a high replacement over a short period of time; these values make this species an important pest of stored amaranth products.