Communications in agricultural and applied biological sciences最新文献

Fusarium head blight (FHB) is one of the major diseases affecting wheat. It is caused by a complex of fungal species, resulting in yield losses and health problems due to mycotoxin production. The presence of multiple fungal species on wheat ears, with varying responses to active fungicide ingredients used in the field, makes the disease difficult to manage. In order to evaluate the efficacy of the timing of applications (at GS 39, GS 61 and GS 39+61) of a prothioconazole + fluoxastrobin-based fungicide, a 2-year field trial was conducted in Belgium. In both years, applications at GS 61 and GS 39+61 resulted in a significant reduction in symptom severity on ears and in deoxynivalenol (DON) content compared with the untreated control in 2013. In 2012, when Microdochium spp. were the most prevalent species, the treatment at GS 39 significantly reduced ear symptoms. Fusarium graminearum was predominant in the second year (2013) and caused significant DON accumulation in the grain after a single foliar spraying. The two genera were characterized by distinct types of symptoms: grouped bleached spikelet's for F. graminearum and isolated bleached spikelet's for Microdochium spp. This difference enabled the significant effect of the double treatments on symptoms caused by Microdochium spp. to be determined in the second year. This effect, which was also visible on leaf symptoms, suggests that Microdochium spp. epidemics in wheat might be polycyclic. Discrimination between symptoms caused by F. graminearum and Microdochium spp. could be a useful tool to study FHB management using fungicide treatments.

During the latest outbreak of the gypsy moth in Serbia (2009-2014), some areas of Central Serbia were particularly endangered, and one of them was Krusevac region, where the forests give way to orchards in the pattern resembling the tiger's skin. Since the number of the laid egg masses in the autumn 2013 guaranteed the defoliation of both forest tree species and agricultural crops, and the presence of E. maimaigo, in Central Serbia had already been determined, at 30 selected plots the assisted spread of it was performed, through the introduction of the infectious inoculum in the beech and oak forests which border the orchards. Since there was dealt with the living organism--fungus, which is particularly susceptible to the weather conditions (temperature and air humidity, as well as the precipitation), and under the conditions of the global warming and great drought, the special recipe for the preparation of inoculum was made. In the following year the mass epizootic of the gypsy moth caterpillars, of the younger instars (L2 and L3), occurred, which implies that E. maimaiga caused the crash of the outbreak of this most harmful species of the defoliating insects of the forests and orchards.

During agricultural activities, large amounts of insecticides and herbicides are used for controlling pests. The overspraying of pesticides may contaminate freshwater bodies, as well as having a significant effect on aquatic animals. To determine the potential risk of pesticides, the acute toxicity of insecticides and herbicides on the nauplii fairy shrimp, Branchinella thailandensis were evaluated. The organisms were exposed to different concentrations of insecticides (chlorpyrifos and carbaryl), and herbicides (paraquat and 2,4-D) for 24 h, after which the LC50 values were compared. The acute toxicity tests determined that the LC50 values of chlorpyrifos and carbaryl after 24 h were 0.00186 mg/L and 0.21 mg/L, respectively. For herbicides, paraquat and 2,4-D, the LC50 values were 0.11 mg/L and 27.91 mg/L. Therefore, chlorpyrifos insecticides were found to be more toxic than herbicides (2,4-D and paraquat) with regard to the nauplii fairy shrimp. The high toxicity of pesticides has a long-term, and potentially damaging effect on aquatic organisms in the application areas.

A high number of side-effects trials were developed and carried out on beneficial insects and mites by the 'Side-effects on beneficial organisms' IOBC working group and subsequently published in the IOBC bulletins over a number of years. In general, these tests were mainly carried out under laboratory and/or semi-field conditions following the very worst case scenario applications, leading to an IOBC classification of 3 (moderately toxic) and 4 (harmful) for many of the tested compounds However, feedback from applications under practical conditions, often indicated that the published results were far from realism for a number of compounds. Due to the fact that some of these active ingredients are still regularly used, or even growing in importance, a number of them were tested on many beneficial arthropods and pollinators and the upcoming results were compared with the registered IOBC data. Among these compounds, Tau-fluvalinate (Mavrik), a widely used synthetic pyrethroid against aphids, caterpillars and beetles in a large number of crops, was tested in the facilities of IPM Impact. While this compound was often considered as being very toxic for all beneficial organisms, slightly toxicity was shown on adults of Aphidius colemani (Hymenoptera: Aphidiidae), and larvae of Chrysoperla carnea (Neuroptera: Chrysopidae) and Anthocoris nemoralis (Heteroptera: Anthocoridae). However, the moderately toxicity or toxicity appeared on adults of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) as well as larvae of Adalia bipunctata (Coleoptera: Coccinellidae) and Episyrphus balteatus (Diptera: Syrphidae), was moderated by short persistence of less than 3 days. Concerning large earth bumblebee, Bombus terrestris (Hymenoptera: Apidae), the compound was characterized as completely safe, even when being sprayed in the full flight phase of the bumblebees. This indicates that for a high number of pollinator species and some of the most important beneficial insects, tau-fluvalinate can be applied without any restriction in IPM schemes in the majority of crops. Furthermore, the appropriate application time may lead to hardly any residual effects on other beneficials in practice.

Our work provides the first evidence for elicitation and protection effects of preventive treatments with oligosaccharides (20%)-based new formulation (Oligos) against Mycosphaerella graminicola, a major pathogen of bread wheat (BW) and durum wheat (DW). In planta Oligos treatment led to strongly reduced hyphal growth, penetration, mesophyll colonization and fructification. During the necrotrophic phase, Oligos also drastically decreased the production of M. graminicola CWDE activities, such as xylanase and glucanase as well as protease activity in both wheat species, suggesting their correlation with disease severity. Concerning plant defence markers, PR2, Chi 4 precursor-, Per- and LOX-1-encoding genes were up-regulated, while glucanase (GLUC), catalase (CAT) and lipoxygenase (LOX) activities and total phenolic compound (PC) accumulation were induced in both (non-inoculated and inoculated contexts. In inoculated context, a localized accumulation of H2O2 and PC at fungal penetration sites and a specific induction of phenylalanine ammonia-Lyase (PAL) enzymatic activity were observed. Moreover, our experiment exhibited some similarities and differences in both wheat species responses. GLUC and CAT activities and H2O2 accumulation were more responsive in DW leaves, while LOX and PAL activities and PC accumulation occurred earlier and to a stronger extent in BW leaves. The tested Oligos formulation showed an interesting resistance induction activity characterized by a high and stable efficiency whatever the wheat species, suggesting it integration in common control strategies against STB on both DW and BW.

Galia melons are produced in southeast Spain and exported to other European countries. The main problem of melons during transport and storage consists of the development of epiphytic populations of fungi living inside the netting areas located on fruit surface. These areas are natural wounds which are covered by local suberin and lignin secretion induced by the plant in response to the natural skin wounds which occurs during fruit growing. These fungi are growing from the scarce organic matter and nutrients that are either deposited or segregated from the fruit. Several genera of fungi have commonly been associated to those areas such as some species of Fusarium, Cladosporium sp. and Alternaria sp. and a few others. All microorganisms were living in an ecological equilibrium. However, when water was present inside the netting areas, the growth of Cladosporium sp. was exacerbated and then, the ecological equilibrium was broken, therefore these grey areas turned to green-dark colour due to hyphal development of this fungus. This process deteriorated visual quality of fruits, therefore the increase of losses during transport and storage were noticeable. A relative humidity very high, round 100% or a thinner layer of water condensed in these areas were sufficient to increase epiphytic development of Cladosporium without causing decay, even at refrigeration temperature. However, when relative humidity was lower than about 98%, no growth of aerial hyphae of Cladosporium was observed. In contrast, some brown stains round netting areas were developed due to the growth of the fungus through skin layers causing severe decay after 32 days of storage at 7 degrees C. When the affected fruits were transferred at ambient temperature, aerial mycelium of Cladosporium emerged from those brown skin areas exacerbating the losses. In conclusion, water condensation should be avoided to prevent epiphytic development of Cladosporium. If washing treatment of fruits is carried out during commercial handling, they must be dried before storage. In addition, storage period higher than 16 days at 7 degrees C and relative humidity higher than 98% must be avoided in order to prevent Cladosporium rot.

In potted azalea (Rhododendron simsii hybrids) the broad mite Polyphagotarsonemus latus (Banks) is considered a severe pest with an important economic impact. Although chemical control is available, permitted acaricides are limited and have a restricted number of applications. Therefore, growers have a keen interest in alternative control measures. Recently, research on the behaviour and population dynamics of P. latus on azalea leaf disks stored at different temperatures indicated that survival and reproductive capacity of broad mite is reduced drastically when temperature drops below 7°C. In Flanders, storage of azalea plants at 3°C is common practice to pause flower development (in function of the date that plants have to be ready for sale) before forcing them to flower in a heated greenhouse. Hence, an experiment was set-up to verify and quantify the effect of cold storage of azalea on broad mite infection. Azalea plants were infected with P. latus and stored at 3°C for 2, 3 or 4 weeks. Then, plants were transferred to a heated greenhouse for 2 weeks to check whether surviving female broad mites were still able to reproduce. The number of P. latus on azalea was assessed before cold treatment, immediately after treatment, and 2 weeks after transfer to the heated greenhouse. Results confirmed that cold storage can play a role in broad mite control as the P. latus population was significantly reduced (up to 90%) immediately after treatment. A further decrease in the number of P. latus during storage in the heated greenhouse indicated that cold treatment during 4 weeks had also an effect on the reproduction capacity of P. latus. We conclude that cold storage of azalea plants (at least 4 weeks at maximum 3°C) should be considered as an additional and alternative control method for P. latus at the end of the azalea production cycle.

Anthocoris nemoralis, Anthocoris nemorum and Orius spp. are not the only beneficial predatory bugs inhabiting pear orchards in Belgium. Quite often, the Miridae bugs Heterotoma spp. and Pilophorus spp. can be found during spring and summer in these orchards, thereby feeding on several pests such as psyllids, aphids, spider mites, ... . Side-effects are usually assessed on Anthocoris and Orius spp., but due to the potential importance of Miridae bugs in pest reduction, we tested some commonly used crop protection products used in pear cultivation on Heterotoma planicornis and Pilophorus perplexus (residue-based tests in petri-dishes). One day after treatment, mortalities already could be observed for some products. Seven days after treatment, abamectin, deltamethrin and thiacloprid were considered the most toxic products as stated by the IOBC classification. This outcome was then analysed with regard to different treatment schedules, providing insights in potential side-effects on crop protection treatments on the composition of beneficial fauna in pear orchards.

The aim of the study was to assess the bio-efficacy of four Alpinia galanga rhizome crude extracts against the second and third instars of Spodoptera litura, an important field pest. The growth of younger larvae was significantly affected while that of the older larval stage was less influenced. In both stages, the methanol crude extract showed the greatest efficiency which caused the highest number of abnormal adults to occur and produced a large LD₅₀ value (12.816 µg/ larvae) pupicidal percentage after treatment, whereas, hexane extract caused the highest mortality during the larval-pupal stage after treatment with an LD₅₀ value of 6.354 µg/ larvae. However, the larval development was not significantly different among all treated larvae compared to the control. This study suggests that secondary larval instars of S. litura are more susceptible to the larval growth inhibitory action of Alpinia galanga extracts and these extracts could also be applied for use in the management of pests.

In this study, biological activity of entomopathogenic fungi (4 strains) isolated from the Colorado potato beetle and the commercial biopesticides containing entomopathogenic fungi; Priority® (Paecilomyces fumosoroseus), Nibortem® (Verticillium lecanii), Nostalgist® (Beauveria bassiana), Bio-Magic* (Metarhizium anisopliae), Bio-Nematon* (Paeciliomyces sp.) and plant extracts; Nimbedicine EC* (Azadiractin) were determined against Leptinotarsa decemlineata under laboratory conditions. An Imidacloprid active ingredient commercial insecticide was also used to compare the insecticidal activity and distilled water was used as control. The biological control agents were applied to 2nd-3rd larval instars, 4th larval instars and adults with spray and leaf dipping methods. Single concentration (10⁸ conidia/mL⁻¹) of entomopathogenic fungi and recommended dose of bioinsecticides were prepared for application. The number of dead insects were determined at 3, 5, and 7 days after applications. Experiments were conducted at 25 ±1° C and 60% ± 5 relative humidity with 16:8 h light: dark conditions. Entomopathogenic fungi and bioinsecticides were found to be more effective on larval stage than 4th larval instars and adults. In spray methods, Bio-Magic®, Nibortem®, and Nostalgist® caused 96.4%, 92.9% and 82.1% mortality on 2nd larval instars and 20%, 36.7% and 33.3% mortality on adults, respectively. All local fungal isolates (B. bassiana) applied on 2nd and 4th larval instars caused 100% mortality. Adults showed 58.6-86.2% mortality.