Insecticide potential of citrus essential oils and non-target impact on a predatory bug, on enzymatic activity of the plant and of the soil microbioma

BIONDI, ANTONIO; DESNEUX, N.; GENNARI, M.; PALMERI, V.; SISCARO, G.; RICUPERO, MICHELE; CAMPOLO, O.; BARBAGALLO, R. N.; DI PIETRO, P.; CHERIF, A.; LEBDI-GRISSA, K.; GABELLONE, CECILIA S.; SATRIANO, C.; MIRANDE, LUCIANA; ZAPPALA, LUCIA; SCHNEIDER, MARCELA I.

Padua

Congreso; XXV Italian National Congress of Entomology.; 2016

The discovery of new insecticidal substances with low environmental impact is crucial for developing sustainable pest control strategies. Recently, increasing importance is given to natural origin substances, such as botanicals. In particular essential oils (EO) have recently shown good potential for controlling several insect pests. In this context, this research consortium aims at assessing the target and non-target toxicity of citrus EOs on tomato crop.The pest control efficacy of three EOs, as emulsion and nanoencapsulated with PEG (EO-PEG), was tested at various concentrations on juveniles of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), by ingestion or by residual contact. The highest concentration was used to assess the lethal and sublethal effects on the mirid predator Nesidiocoris tenuis Reuter, on the enzymatic activity of the soil microbioma (urease, acid phosphomonoesterase and dehydrogenase) and of the plant (ascorbate peroxidase, catalase and superoxide dismutase).The target toxicity varied depending on the tested instar, route of exposure and formulation. Pest eggs were overall the less susceptible instar and sweet orange-PEG was the most efficient on it. Sweet orange and mandarin-PEG were the most toxic toward larvae following topical and ingestion exposure, respectively. All tested substances showed oviposition repellence potential. The nanoformulation reduced the phytotoxicity of the EO applications on tomato leaves significantly.Predators exposed to fresh EOs-PEG residues survived significantly less than the untreated control, but significantly more than those exposed to two commercial insecticides (indoxacarb and spinosad). However, significant reduction of the fertility of the exposed insects was registered even after 7 days of the treatment. No negative effects were seen on the enzymatic activities of the soil and of the plant, with particular reference to those linked to the elicitors of plant defenses. Altogether, these data suggest that citrus EOs and the nanoencapsultaion process could improve the sustainability of current integrated and organic control programs in tomato crops.