Insecticidal effects of native raw and commercial diatomaceous earths against lesser grain borer and granary weevil under different environmental conditions

Authors: OGRETEN, AYHAN - Plant Protection Research Institute; EREN, SEDAT - Harran University; MUTLU, CETIN - Harran University; AYAZ, TARKAN - Siirnak University; BINGHAM, GEORGINA - University Of Nebraska; Morrison Iii, William

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2025
Publication Date: 5/22/2025
Citation: Ogreten, A., Eren, S., Mutlu, C., Ayaz, T., Bingham, G.V., Morrison Iii, W.R. 2025. Insecticidal effects of native raw and commercial diatomaceous earths against lesser grain borer and granary weevil under different environmental conditions. Insects. https://doi.org/10.3390/insects16060549.
DOI: https://doi.org/10.3390/insects16060549

Interpretive Summary: Stored grain pests lead to substantial economic losses of cereal grains after harvest. Although insecticides are essential components for pest management in stored grain, resistance has become problematic and consumer demand for food products free of pesticide residues is growing. Diatomaceous earths (DEs), which consist of microscopic, fossilized diatoms, are a safe and environmentally friendly method of pest control. However, their effectiveness is influenced by temperature, relative humidity, dose, and target species. We evaluated three DEs (two of which are new, Ankara, Aydin, and an existing commercial product, Silico-Sec) on the mortality of two important and widespread stored wheat grain pests, including lesser grain borer and granary weevil at multiple doses from 250-1000 ppm and at two temperatures (25 and 30ºC) and relative humidity levels (40 and 60%). Overall, all DEs caused higher mortality in granary weevil than lesser grain borer. One hundred percent mortality was achieved for granary weevil in all three DEs at 1000 ppm and 30ºC and 40% relative humidity. By contrast, Aydin DE was the most effective DE against lesser grain borer, which was associated with 85% mortality at 30ºC and 40% relative humidity. Although survival occurred at lower DE concentrations, adults from both species were unable to produce any offspring when placed in untreated grain. Thus, our study shows that the effectiveness of these two new DEs are comparable to a commercially available product, and could be used under a variety of temperature conditions. This will help strengthen IPM options for grain storage pests.

Technical Abstract: Stored grain pests are a major challenge during the storage of cereal grains, leading to substantial economic losses. Insecticides have been an essential component of stored grain pest management for a long time. Nevertheless, new approaches are required for pest management due to mounting evidence of pesticide resistance and negative effects of pesticides on ecosystems and human health. Diatomaceous earths (DEs) are a safe and environmentally friendly method of pest control. However, their effectiveness is influenced by temperature, relative humidity, dose, and target species. This study investigated the insecticidal effects of two native raw (Ankara and Aydin) and one commercial (Silico-Sec) DEs on the mortality of two important stored wheat grain pests [i.e., Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) and Sitophilus granarius L. (Coleoptera: Curculionidae)]. Five different doses of all DEs (0, 250, 500, 750, and 1000 ppm) were tested under two temperatures (25ºC and 30ºC) and two relative humidity levels (40% and 60%). Mortality was recorded at 7, 14 and 21 d after treatment (DAT). Overall, all DEs caused higher mortality in S. granarius than R. dominica. The highest dose of each DE caused the highest mortality of S. granarius at 30 ºC temperature and 40% relative humidity. Aydin DE caused higher mortality than Ankara and Silico-Sec; however, the mortality did not reach 100% even 21 DAT in S. granarius. By contrast, the highest dose of Aydin DE caused 100% mortality in R. dominica under 30 ºC and 40% relative humidity at 21 DAT. Nevertheless, all DEs caused ~85% mortality in R. dominica at 14 DAT. The surviving adults of both species were unable to produce F1 progeny indicating the success of all DEs. The farmer storage facilities have similar climatic conditions in Türkiye where the DEs exhibited the highest insecticidal efficacy in the current study. Therefore, native raw Aydin DE can be successfully used for the management of both species in Türkiye.