Organic side-streams and agricultural wastes represent a big pool of untapped and underrated resources which could be efficiently exploited for insect rearing. We evaluated the suitability of eleven agricultural by-products, stemming from the production of cotton, sugar beet, sunflower, barley, oats, peas and vetch, for the development of larvae of the yellow mealworm, Tenebrio molitor. In a first bioassay, by-products were screened singly to evaluate their potential to support the development of middle sized (4th-6th instar) larvae. In a second bioassay, by-products were supplemented with carrot, and their potential to support complete larval development (first instar until first pupation) was evaluated. Lastly, a third bioassay was conducted in which the more promising by-products were used as components of isonitrogenous diets for middle sized larvae, at two nitrogen levels (2.7 and 3.2%). Our results show the suitability of several agricultural by-products from Greece for T. molitor larvae. The best results though were obtained with the oat and the barley by-product (class II), tested either singly or mixed in diets. These by-products can be utilised singly or in composed diets and can greatly decrease the feed costs of mealworm production. Moreover, the results obtained from the isonitrogenous diets bioassay, show that besides nitrogen content, other factors need to be considered when formulating optimal diets. Our study aims to implement circular economy practices in insect farming at a local level.

Diatomaceous earth (DE) formulations are promising alternatives over the use of traditional insecticides. In the present study, a series of laboratory bioassays was carried out to assess the efficacy of three diatomaceous earth formulations, i.e., Silicid, Celatom® MN-23, and SilicoSec®, for the control of a wide range of stored-product insect species in soft wheat. The species tested were Tribolium confusum, Tribolium castaneum, Sitophilus oryzae, Sitophilus granarius, Rhyzopertha dominica, Oryzaephilus surinamensis, and Alphitobious diaperinus. Different dose rates, i.e., 0 (control), 100, 300, 500, and 1000 ppm, were used for each of the aforementioned dust formulations. Mortality levels of the exposed individuals were assessed after 3, 7, 14, and 21 days of exposure. Moreover, progeny were counted 65 days later. Based on our results, dust formulations were effective for the control of most of the stored-product beetle species tested. Among the DE formulations tested, Silicid could adequately control the stored-product insect species. Complete suppression of offspring was observed only for secondary species (T. confusum, T. castaneum, O. surinamensis, and A. diaperinus). For primary species (S. oryzae, S. granarius, and R. dominica), the lowest number of progeny was observed in wheat treated with Silicid. For instance, in the case of R. dominica, significantly fewer individuals were produced in Silicid-treated wheat at the highest dose rate. The results of the present study aim to encourage the utilization of DE in stored-product protection as an integrated pest management tool. Additional experimentation is required to apply the tested DE formulations in the field and on different surfaces.