Pilot study on the effect of a standardized earthworm humus extract on the populations of pest insects in a productive olive grove.

In the present study, the standardized, aqueous extract of earthworm humus, BioremiqΤΜ by Green Arsenal, which in Hungary, its country of origin, is licensed for use in organic crops as a growth enhancer and natural fertilizer. During April and July 2021, the effect of the product on the insect populations, present in an irrigated, conventional, productive olive grove, in Vartholomio, Prefecture of Ilia, was recorded. The product is reported to aid soil fertility restoration, plant growth stimulation, reduction of the negative effects of adverse weather conditions and increase of tolerance to various plant pathogens and pests. The analysis of its components shows a high content of macro- and trace elements, natural enzymes and hormones that contribute to healthy plant growth, while they seem to improve soil structure, improving the ability of plants to absorb nutrients, resulting in a quality and quantity produce increase. It is recommended for frequent use at all kinds of crops, mainly olive and various vegetables, and is applied both by foliar application and root irrigation. For the requirements of the study, we selected an 11-year-old olive grove, where the variety “Koroneiki” is cultivated, at of 7 x 7m distance. The experimental plot consisted of three rows of ten trees each: row E (application of BioremiqΤΜ), row M (no intervention) and row C (according to the producer's program). In row E, five Bioremiq® applications were performed, every 15 days, the first with root irrigation, the following foliarly, with 3L and 1L / acre respectively, according to the manufacturer's instructions. To record the insect populations, 10 days after each application, 4 branches (~ 20cm) were sampled from each tree, one from each side, a total of 40 branches from each row, 120 from the entire plot. Each branch was placed individually in a plastic bag and stored in the refrigerator until completion of the study. Significant presence of the harmful insects Prays oleae, Palpita unionalis, Euphyllura olivina and Liothrips oleae was recorded, while we also detected a scattered presence of Rhynchites cribripennis, Dasyneura oleae, Drosophila suzuki, Chrysopa sp. and Mantis religiosa and of the mites Tetranychus urticae and Eriophyes oleae. The results were studied on Excel for trend visualization and then put into SPSS for statistical comparison. There was an obvious trend of population decline, probably also due to climatic factors; nevertheless, a clear statistically significant difference was observed between the BioremiqΤΜ and conventionally treated rows compared to the control, for all insect species. A statistically significant difference (paired value t-test) between BioremiqΤΜ and the control was clear for L. oleae (p value = 0.033) and P. unionalis (p value = 0.317), at 95% significance level.