Thymus Citriodorus (Schreb) Botanical Products as Ecofriendly Nematicides with Bio-Fertilizing Properties

Abstract

In recent years, interest has surged in the development of plant extracts into botanical nematicides as ecofriendly plant protection products. Aromatic plants are maybe the most studied category of botanicals used in this direction and the yielding essential oils are obtained on a commodity scale by hydro distillation. Nevertheless, can the bioactivity of aromatic plants always be attributed to the terpenes content? What would it mean for soil microcosms to bear the treatment of an essential oil to cure against Meloidogyne sp.? Are there other extraction procedures to prepare more ecofriendly botanical products starting from an aromatic material? Lemon thyme is studied herein for the first time for its nematicidal potential. We compare the efficacy of lemon thyme powder, macerate, water extract and essential oil to control Meloidogyne incognita (Chitwood) and Meloidogyne javanica (Chitwood), and we additionally study the secondary effects on soil microbes and free-living nematodes, as well as on tomato plant growth. According to our results lemon thyme powder enhances tomato plants’ growth in a dose-response manner and when it is incorporated in soil at 1 g kg−1, it exhibits nematicidal activity at a 95% level on M. incognita. The water extract yielding from the same dose is nematicidal only if it is left unfiltered; otherwise only a paralysis effect is demonstrated but inside the soil the biological cycle of the pest is not arrested. The essential oil is good both in performing paralysis and biological cycle arrest, but it detrimentally lowers abundances of bacterial and fungal feeding nematodes. On the contrary, lemon thyme powder and unfiltered water extract augments the bacterial biomass, while the latter also increases the bacterivorous nematodes. Overall, the bio fertilizing lemon thyme powder and its unfiltered water extract successfully control root knot nematodes and are beneficial to soil microbes and saprophytic nematodes.

Polysulfides Applied as Formulated Garlic Extract to Protect Tomato Plants against the Root-Knot Nematode Meloidogyne incognita

“…Overall, the highest concentration presented, 2 mg/mL, showed the strongest controlling effect on J2, resulting in no root galls after the J2 were incubated for 48 h and 96 h to NEMguard ® DE. These findings are in line with previous investigations, showing that the nematicidal potential of the NEMguard ® solution (NEMguard ® SC), a different formulation as the one we used for our study against M. incognita , is concentration and time dependent [ 20 , 26 ].…”

Impacts of Decaying Aromatic Plants on the Soil Microbial Community and on Tomato Seedling Growth and Metabolism: Suppression or Stimulation?

“…The enhancement of soil enzymatic activity and total microbial biomass by spearmint essential oil is also reported in [ 14 ]. Recently, a study on the impacts of Thymus citriodorus on soil communities and tomato growth showed that different plant parts had different impacts, suggesting the intervention of specific chemical constituents that were included or not in each plant part, and that soil bacterial biomass increased, whereas fungal biomass did not change in its presence [ 29 ]. In contrast, our findings showed a clear positive impact of mint and rosemary leaves on fungi, particularly at the early stages of the decomposition process.…”

“…In this context, spearmint composts [ 26 ] or leaves [ 27 , 28 ] incorporated at different rates in the soil, stimulated the growth of tomato plants remarkably while also suppressing weed emergence, particularly of broadleaved species [ 26 ]. Other aromatic plants such as Thymus citriodorus were also found to exert a beneficial effect on tomato growth while successfully controlling root knot nematodes [ 29 ].…”

Nematicidal Activity of Stevia rebaudiana (Bertoni) Assisted by Phytochemical Analysis

“…Six plastic bags represented the experimental treatments, 1kg of soil each receiving a nematode inoculation 2500 J2 kg −1 . After appropriate mixing and overnight incubation at room temperature according to Ntalli et al, 2020 [50] the plastic bags were spiked with appropriate amounts of LP and WP to reach the test concentrations of 1, 5, 10, 50, and 100 g kg −1 soil. NEMguard SC (garlic extract by Intrachem) was used as a commercial control at the recommended dose (4 L ha −1 that is 2 µL of formulated product per kg soil or 2 mg of a.i per kg of soil) [51].…”