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- Earthworms and their cutaneous excreta can modify the virulence and reproductive capability of entomopathogenic nematodes and fungiPublication . Chelkha, Maryam; Blanco-Pérez, Rubén; Vicente-Díez, Ignacio; Bueno-Pallero, Francisco; Amghar, Souad; El Harti, Abdellatif; Campos-Herrera, RaquelEarthworms are ecological engineers that can contribute to the displacement of biological control agents such as the entomopathogenic nematodes (EPNs) and fungi (EPF). However, a previous study showed that the presence of cutaneous excreta (CEx) and feeding behavior of the earthworm species Eisenia fetida (Haplotaxida: Lumbricidae) compromise the biocontrol efficacy of certain EPN species by reducing, for example, their reproductive capability. Whether this phenomenon is a general pattern for the interaction of earthworms-entomopathogens is still unknown. We hypothesized that diverse earthworm species might differentially affect EPN and EPF infectivity and reproductive capability. Here we investigated the interaction of different earthworm species (Eisenia fetida, Lumbricus terrestris, and Perionyx excavatus) (Haplotaxida) and EPN species (Steinernema feltiae, S. riojaense, and Heterorhabditis bacteriophora) (Rhabditida) or EPF species (Beauveria bassiana and Metarhizium anisopliae) (Hypocreales), in two independent experiments. First, we evaluated the application of each entomopathogen combined with earthworms or their CEx in autoclaved soil. Hereafter, we studied the impact of the earthworms’ CEx on entomopathogens applied at two different concentrations in autoclaved sand. Overall, we found that the effect of earthworms on entomopathogens was species-specific. For example, E. fetida reduced the virulence of S. feltiae, resulted in neutral effects for S. riojaense, and increased H. bacteriophora virulence. However, the earthworm P. excavates increased the virulence of S. feltiae, reduced the activity of H. bacteriophora, at least at specific timings, while S. riojaense remained unaffected. Finally, none of the EPN species were affected by the presence of L. terrestris. Also, the exposure to earthworm CEx resulted in a positive, negative or neutral effect on the virulence and reproduction capability depending on the earthworm-EPN species interaction. Concerning EPF, the impact of earthworms was also differential among species. Thus, E. fetida was detrimental to M. anisopliae and B. bassiana after eight days post-exposure, whereas Lumbricus terrestris resulted only detrimental to B. bassiana. In addition, most of the CEx treatments of both earthworm species decreased B. bassiana virulence and growth. However, the EPF M. anisopliae was unaffected when exposed to L. terrestris CEx, while the exposure to E. fetida CEx produced contrasting results. We conclude that earthworms and their CEx can have positive, deleterious, or neutral impacts on entomopathogens that often coinhabit soils, and that we must consider the species specificity of these interactions for mutual uses in biological control programs. Additional studies are needed to verify these interactions under natural conditions.
- Trichoderma gamsii as a biological control agent of turfgrass diseasesPublication . Coelho, Luísa; Dionísio, Lídia; Bueno-Pallero, Francisco; Reis, Mário; Duarte, J.; Guerrero, CarlosGolf is a growing and economically important activity in Portugal with direct and indirect incomes respectively over 350 and 1.450 million of euros, corresponding nearly 1.25% of the Gross National Product. The correct maintenance of lawns in a sustainable manner is required. Sport lawns are quite susceptible to soil-borne diseases1 , which cause enormous economic losses, making environmental friendly disease control methods a practice to develop. The increasing interest regarding environment and public health protection have been increased the search for alternatives, leading researchers to seek strategies to reduce the use of synthetic products, such as fertilizers and pesticides2 . Also, the European legislation is directing the reduction of pesticides3 , facing itself towards more sustainable policies.
- Effects of compost application on nematode populations and the yield of a carrot cropPublication . Coelho, Luísa; Reis, Mário; Bueno-Pallero, Francisco; Guerrero, Carlos; Gonçalves, M. A.Composts may be used either in soilless cultivation or applied to soil, increasing its organic matter content and improving the physical, chemical and biological properties. This study evaluated the effects of compost application to the soil cropped with carrot on nematodes diversity, biocontrol of phytopathogenic nematodes and crop yield. A commercial compost (Organical®, TerraFértil, Portugal) was applied to a sandy soil, at the rate of 0, 12.5, 25, 50 and 100 t ha-1 and incorporated to a 15 cm depth. A carrot crop (Daucus carota L.) was sown with a density of 62.5 plants m-2. At the end of the growing period, when the longer roots had reached about 15 cm, plant growth and yield were quantified. Compost increased carrot yield. Following harvest, soil samples were collected near the roots (root zone) and randomly at three soil depths: 0 to 15 cm, at 30 cm and at 50 cm. Nematodes species were identified and quantified in these four zones, and the damages observed were ranked. Compost influenced nematode populations. Near the roots beneficial nematode populations increased with the compost rate application. Phytopathogenic nematodes were present mainly in the treatments with less compost. Furthermore, nematode genera were distributed according to soil depth. Bacteriophage/saprophyte nematodes were found mainly at 50 cm depth, at the surface and in the root zone. Plant parasitic nematodes were located near the surface (0-15 cm) and at 50 cm depth. Predator nematodes prevailed near the surface, in the root zone and at 50 cm depth. The lower populations of nematodes were found at 30 cm depth. This work showed that the dynamics of nematode populations in the soil is affected by soil depth and compost dose, suggesting that compost can reduce the population of phytopathogenic nematodes and increase bacteriophage/saprophyte and predator nematode populations.