Suitability of Poaceae seeds for Plodia interpunctella development

One of the most important pests of stored grains is Plodia interpunctella (Hübner), whose larvae feed primarily on germinal part of the kernels, causing a reduction of seed germination and seed viability. This is detrimental for seeds of high category. However, seeds of different species within the same taxonomic family have different morphology (thickness of seed-coat, presence or absence of palea, palea loose or firmly attached to the seed etc.), which affects the susceptibility of seeds to P. interpunctella attack. The hypothesis was that seed hardness and the absence of palea could also significantly influence the life history of this pest. We assessed the suitability of different seeds from family Poacae (maize, wheat, barley, oats, ray, forage sorghum (variety), forage sorghum (hybrid), Sudan grass and millet) for P. interpunctella development and seeds susceptibility to pest attack (expressed in Susceptibility index –SI). The following parameters were monitored: larval mortality, adult emergence, mean developmental duration (from egg to adult) and female fecundity. Observations were carried out weekly, for 49 days. Data were statistically analyzed using Duncan’s multiple range Test. The highest larval mortality, the lowest number of emerged moths and the lowest fecundity were recorded on millet, Sudan grass and forage sorghum (variety and hybrid). However, the shortest larval development (27.8 days) and the highest fecundity (109.5-115.6 eggs) were on standard laboratory diet, maize and wheat. Morphometric measures of moths indicate that on unsuitable mediums like millet, Sudan grass, and different sorghum varieties the body lengths were statistically significantly shorter (0.5-0.6 cm) compared to other treatments (0.8-0.9 cm). According to the SI, the most susceptible were maize, wheat, barley, oats and ray, while moderately resistant were Sudan grass and millet. Testing kernel hardness and continuous improving of kernel resistance to storage insect pests could provide lower losses in stored grain quality and quantity.