Possible use of Inula viscosa (Dittrichia viscosa L.) for biostimulation of Oscularia deltoides and Corpuscolaria lehmanii plants and protection against Aphis nerii

In this study the possibility of using liquid Inula viscosa (Dittrichia viscosa L.) to improve the growth and quality of Oscularia deltoides and Corpuscolaria lehmanii plants and protection against Aphis nerii was evaluated. The 3 experimental groups in cultivation were: i) group without the use of Inula viscosa liquid macerate (CTRL), irrigated with water and previously fertilised substrate; ii) group treated with 1% of Inula viscosa liquid obtained from flowers (leaf spraying and soil irrigation), previously fertilized substrate (INU1); iii) group treated with 1% of Inula viscosa liquid obtained from leaves and stems (leaf spraying and soil irrigation), previously fertilized substrate (INU2). The test showed a significant increase in the agronomic parameters analyzed in plants treated with liquid Inula viscosa. In fact, all plants treated with Inula showed a significant increase in plant height, leaves number, vegetative and roots weight, branches and flowers number and flowering time in both Corpuscolaria lehmanii and Oscularia deltoides. An evaluation was also made of the number of individuals of Aphis nerii present on the plants of Corpuscolaria lehmanii and Oscularia deltoides to assess whether the macerate of Inula can be used for the control of these insects. The GC-MS analysis of active fractions strongly suggested costic acid as the compound responsible for contact toxicity against Aphis nerii. Probably in the plant treated with Inula viscosa there is an induction of the defense mechanisms that lead to greater resistance to biotic and abiotic stresses. The application of Inula macerate also improves the plant's defences against attacks by fungal pathogens and insects. Very interesting aspects, especially in view of a possible reduction of fertilizers and synthetic plant protection products.