Natural Formulation Based on Diatomaceous Earth and Botanicals against Stored Product Insects

SIMPLE SUMMARY: Stored product insects play a major role in postharvest loss. In order to minimize negative effect of conventional insecticides, diatomaceous earth (DE) is one of the alternative solutions for insect control. Despite favorable effect for the environment and human health, DE has some negative side effects on the treated commodity. In order to overcome the limitations of DEs, the aim of this study was to develop natural formulation which would improve the activity of DE. Formulation (labeled as N Form) based on DE enhanced with botanicals and silica gel was tested against three major stored product insect species in wheat and barley under controlled conditions. N Form showed higher efficacy than DE, especially in barley, inducing higher mortality of all three insect species. This study provides new information about the improvement of DE effectiveness thus representing a contribution to further development of natural insecticides as a part of integrated pest management. ABSTRACT: Diatomaceous earth (DE) has long been known as a potential protectant for stored cereals against various stored product insects. Despite favorable effect for the environment and human health, DE has some negative side effects on the treated commodity. In order to minimize negative response and to improve its efficacy, this paper represents a study of developed natural formulation based on DE SilicoSec(®) enhanced with botanicals (essential oil lavender, corn oil, and bay leaves dust) and silica gel. The activity of formulation (labeled as N Form) was tested against Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Tribolium castaneum (Herbst) in seed wheat and barley under controlled conditions. As a reference comparative value, DE SilicoSec(®) was used. N Form showed higher efficacy than DE, especially in barley at the lowest concentration, inducing higher mortality of all three insect species. The highest average progeny inhibition was recorded in R. dominica population both in seed wheat and barley with 94.9% and 96.3% of inhibition, respectively, followed with S. oryzae and T. castaneum inhibition of 90.6% and 86.1%, respectively, in wheat and 94.9% and 89.7%, respectively, in barley. Results indicate that the developed natural formulation N Form enhanced the activity of DE SilicoSec(®) using lower amount of DE dust and that it could be successfully implemented for storage of cereals as alternatives to chemical pesticides for stored product insect control.