Field assessment of efficacy of nitrogen salts to control the root-knot nematode (Meloidogyne javanica) on tomato

Influence of different nitrogen salts at electrical conductivity levels (EC2, 4 and 8?mmhos/cm) on tomato and root-knot nematode (Meloidogyne javanica) and their interactions was evaluated under field conditions. It was found that both diammonium phosphate ((NH₄)₂HPO₄) and ammonium sulphate ((NH₄)₂SO₄) were more effective than ammonium chloride (NH₄Cl) in causing an obvious suppression of M. javanica infection on tomato through reducing root galling and nematode reproduction and improving tomato growth and yield and their suppressive effect was similar to that of oxamyl or ethoprophos. At higher ECs, the tested nitrogen salts did not greatly affect pH, EC and salinity of rhizospheric soil except NH₄Cl at EC8 that caused higher EC and salinity over the untreated control which makes NH₄Cl less suitable candidate. Therefore, the use of (NH₄)₂HPO₄ and (NH₄)₂SO₄ alone or in combination with other control measures could control M. javanica and improve the growth and yield of tomato under field conditions.     

Integration between Steinernema feltiae and some of environmental friendly compounds to control Spodoptera littoralis (Lepidoptera: Noctuidae)

The efficacy of different concentrations of the commercial neem-based insecticide, Nimbicidine^® and the ecdysone agonist compound Methoxyfenozide (RH-2485), was evaluated against larvae of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). RH-2485 and Nimbicidine^® significantly (p?<?0.001) reduced adult longevity by 2.7 and 1.9 d at the higher concentrations tested, respectively, but no significant differences were observed at low concentration. The tested compounds strongly affected the reproduction of S. littoralis by producing a high percentage of sterility. Fecundity and fertility were significantly affected by both insecticides. No egg laying has been recorded with the higher concentration 0.5% of Nimbicidine^® and 0.1?ppm of RH-2485, while no significant (p?>?0.05) difference was noticed on total number of eggs laid by the female when lower concentration 0.0001?ppm of RH-2485 was applied in the same stage as compared to the control. In the second part of this study, the invasion rate of Steinernema feltiae was affected by the addition of both Nimbicidine and RH-2485 to the diet of experimental host. At higher concentration of both compounds, the invasion rate was decreased despite the infection rate, while the percentage of invading nematodes increase to 56.7% with the combination treatment indicating a considerable improvement in the efficacy of S. feltiae nematode applied in combination with the lower concentration of Nimbicidine^® over that of nematode alone. On the other hand, the invasion of S. feltiae to the insects that were fed on the diet with the addition of ecdyson compound was strongly decreased with increasing concentration of RH-2485 in host diet.     

Does developmental acclimatization reduce the susceptibility to predation in newt larvae?

Many organisms respond to the heterogeneity of abiotic environmental conditions by plastic modifications of their phenotypes (acclimation or acclimatization). Despite considerable research efforts in this area, the beneficial (adaptive) effect of acclimation or acclimatization is still debated. We examined whether the development of newt larvae (Ichthyosaura alpestris) under different natural light and thermal conditions subsequently altered their susceptibility to predation in sun‐exposed versus shaded tanks in nature. During predation trials in various light and temperature conditions, newt larvae that developed in sun‐exposed warmer tanks consistently suffered from higher predation by dragonfly nymphs (Aeshna cyanea) compared to larvae from shaded or colder tanks. We conclude that higher sun exposure during embryonic and larval development negatively affects antipredator performance even in sun‐exposed tanks: this result is inconsistent with the beneficial acclimation hypothesis. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●● , ●●–●●.     

Properties and Nematicide Performance of Avermectins

In 1979, the anthelmintic activity of abamectin, a mixture of avermectins B_1a and B_1b, was first reported. Since then, multiple articles have investigated avermectins' degradation and its efficacy against a wide variety of pests under different conditions and using different modes of application. However, there is a gap in the literature of analysing abamectin properties and its performance as a non‐fumigant nematicide when applied liquid or granular vs. new avenues of application based on seed and seedling treatment. Therefore, this article reviewed literature to discuss the mode of action, environmental aspects, the nematicidal effectiveness of treatment forms and the range of activity to address these topics.     

Pathogens of Ips amitinus: new species and comparison with Ips typographus

Ips amitinus and I. typographus are two serious pests of spruce in Europe, have similar bionomics and are likely to occur and meet on the same host trees. We therefore hypothesized that the two species support similar levels of similar pathogens. To test this hypothesis, we collected mature beetles from three trap trees at each of eight study sites and determined beetle numbers and pathogen infection levels. In total, 938 mature I. amitinus beetles and 3435 of I. typographus were dissected; five pathogens, as well as intestinal nematodes and endoparasitoids, were detected. The neogregarine Mattesia schwenkei is reported here for the first time as a new pathogen in 9.4% of I. amitinus individuals at one site. Average infection levels of most pathogens (Chytridiopsis typographi, Gregarina typographi, Mattesia schwenkei and parasitoids) were significantly higher in I. typographus than in I. amitinus. Metschnikowia typographi was confirmed only in Ips amitinus, while the microsporidium of Nosema typographi occurred only in I. typographus. Within‐season increases in G. typographi infection levels were documented in Ips amitinus.     

Effects of weed harrowing frequency on beneficial arthropods,plants and crop yield

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Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO2

Chloride (Cl^?) has been recently described as a beneficial macronutrient, playing specific roles in promoting plant growth and water‐use efficiency (WUE). However, it is still unclear how Cl^? could be beneficial, especially in comparison with nitrate (NO₃^?), an essential source of nitrogen that shares with Cl^? similar physical and osmotic properties, as well as common transport mechanisms. In tobacco plants, macronutrient levels of Cl^? specifically reduce stomatal conductance (g_s) without a concomitant reduction in the net photosynthesis rate (A_N). As stomata‐mediated water loss through transpiration is inherent in the need of C₃ plants to capture CO₂, simultaneous increase in photosynthesis and WUE is of great relevance to achieve a sustainable increase in C₃ crop productivity. Our results showed that Cl^?‐mediated stimulation of larger leaf cells leads to a reduction in stomatal density, which in turn reduces g_s and water consumption. Conversely, Cl^? improves mesophyll diffusion conductance to CO₂ (g_m) and photosynthetic performance due to a higher surface area of chloroplasts exposed to the intercellular airspace of mesophyll cells, possibly as a consequence of the stimulation of chloroplast biogenesis. A key finding of this study is the simultaneous improvement of A_N and WUE due to macronutrient Cl^? nutrition. This work identifies relevant and specific functions in which Cl^? participates as a beneficial macronutrient for higher plants, uncovering a sustainable approach to improve crop yield.     

In vitro characterization bioassays of the nematophagous fungus Purpureocillium lilacinum: Evaluation on growth,extracellular enzymes,mycotoxins and survival in the surrounding agroecosystem of tomato

The effects of water stress and temperature on in vitro growth and enzymatic activity of Purpureocillium lilacinum (Sordariomycetes, Hypocreales, Ophiocordycipitaceae) isolates with demonstrated capacity to control Nacobbus aberrans (Secernentea, Tylenchida, Pratylenchidae) were evaluated in this study. Also, saprophytic and endophytic colonization in tomato plants were determined. P. lilacinum was able to grow under the evaluated levels of osmotic and matric stress, but the increase in water stress caused reductions in radial growth rates. Moreover, the fungal isolates produced chitinases, proteases, and leucinostatins under inductive conditions. The nematophagous fungi were able to develop saprophytically (10⁴ CFU g^?1 of soil). Meanwhile, only P. lilacinum SR38 demonstrated endophytic capacity. The results suggest that P. lilacinum can be effectively applied as biocontrol agents of phytoparasitic nematodes in tomatoes under variable agroecological conditions.     

Rapid adaptation to a novel host in a seed beetle (Callosobruchus maculatus): the role of sexual selection

Rapid diversification is common among herbivorous insects and is often the result of host shifts, leading to the exploitation of novel food sources. This, in turn, is associated with adaptive evolution of female oviposition behavior and larval feeding biology. Although natural selection is the typical driver of such adaptation, the role of sexual selection is less clear. In theory, sexual selection can either accelerate or impede adaptation. To assess the independent effects of natural and sexual selection on the rate of adaptation, we performed a laboratory natural selection experiment in a herbivorous bruchid beetle (Callosobruchus maculatus). We established replicated selection lines where we varied natural (food type) and sexual (mating system) selection in a 2 x 2 orthogonal design, and propagated our lines for 35 generations. In half of the lines, we induced a host shift whereas the other half was kept on the ancestral host. We experimentally enforced monogamy in half of the lines, whereas the other half remained polygamous. The beetles rapidly adapted to the novel host, which primarily involved increased host acceptance by females and an accelerated rate of larval development. We also found that our mating system treatment affected the rate of adaptation, but that this effect was contingent upon food type. As beetles adapted to the novel host, sexual selection reinforced natural selection whereas populations residing close to their adaptive peak (i.e., those using their ancestral host) exhibited higher fitness in the absence of sexual selection. We discuss our findings in light of current sexual selection theory and suggest that the net evolutionary effect of reproductive competition may critically depend on natural selection. Sexual selection may commonly accelerate adaptation under directional natural selection whereas sexual selection, and the associated load brought by sexual conflict, may tend to depress population fitness under stabilizing natural selection.