查看更多>>摘要：Potato common scab in an important disease caused by several Streptomyces species that reduces potato tuber quality and market value. Management of common scab is difficult, and no conventional method can reliably control this disease. An alternative approach is the use of plant-beneficial bacteria as biocontrol agents, whose application in the field can significantly reduce common scab incidence and severity. This review begins with the description of the potato common scab disease, the diversity of scab-causing Streptomyces species and their phytotoxins and pathogenicity determinants. Then, we describe the diversity of bacterial strains successfully used to date to suppress potato common scab under controlled and field conditions, their biocontrol mechanisms and the factors influencing the biocontrol success. Finally, we discuss the use of phenazine-producing Pseudomonas spp. as biocontrol agents of potato common scab, an attractive approach supported by ten years of continuous research in our laboratory.
Pollard, K. M.Gange, A. C.Seier, M. K.Ellison, C. A....
10页
查看更多>>摘要：Himalayan balsam (Impatiens glandulifera) is one of the most prolific non-native species in Europe. Since 2014, the highly-specific rust fungus, Puccinia komarovii var. glanduliferae, has been released into Great Britain as a classical biological control agent for this invasive weed. Prior to its release, research focused on ensuring the safety of the pathogen, elucidating its life cycle and verifying its host-specificity. However, limited studies were conducted to determine the likely impact of the rust on its host. Due to difficulties in assessing field populations, unforeseen complexities in the plant-pathogen relationship and the requirement for long-term monitoring, inoculation experiments were conducted to evaluate the effect of the rust on both seedlings and mature plants of Himalayan balsam under semi-natural conditions. The impact of the rust was determined through measuring plant-growth parameters in addition to assessing reproductive output. The rust significantly increased seedling mortality, with up to 80% of seedlings dying as a result of rust infection, or indirectly through the colonisation of secondary pathogens. Mature plants infected with the rust produced fewer leaves with a decrease in total plant biomass. Reproductive output was negatively affected through a reduction in both flower and seed production, but with no observed effects on seed viability. This study demonstrates the high potential of the rust for controlling fully susceptible field populations of Himalayan balsam.
Quintero-Elena, Z. J.Aguilar-Marcelino, L.Castaneda-Ramirez, G. S.Gomez-Rodriguez, O....
5页
查看更多>>摘要：The present study evaluated the in vitro and micro-plot predatory activity of the mite Caloglyphus mycophagus against Haemonchus contortus (L3) and Nacobbus aberrans (J2). To determine the in vitro predation of the mite, four groups were formed in Petri dishes: (1) 5,000-H. contortus, (2) 1,000-N. aberrans (3) 5,000-H. contortus and 5 mites and (4) 1,000-N. aberrans and 5 mites. The plates were kept for 15 days at 28 degrees C. For the evaluation of micro-plots with mites against nematodes, Italian ryegrass was used, and additionally, micro-plots with faecesivermectin/nematodes/mites were used over 15, 30 and 45 days. At each time, two control groups were formed containing 5,000 larvae of H. contortus and 1,000 s-stage juveniles of N. aberrans, respectively, and two treated groups containing the same amounts of nematodes as the controls and 5 mites on each micro-plot. The results showed an in vitro reduction of 72.86% for N. aberrans and 42.17% for H. contortus. For the micro-plot experiment at 45 days, the percentage of reduction was 78.95 and 63.16% for H. contortus and N. aberrans, respectively. In the case of the micro-plots with ivermectin, mite mortality was 100%. The mite C. mycophagus showed activity in vitro , in the micro-plot against H. contortus and N. aberrans. In addition, we provide evidence that iver-mectin in cattle faeces leads to a 100% mortality for C. mycophagus in micro-plots.
查看更多>>摘要：Pyrethroid insecticides are the only strategy to control Triatoma infestans populations (Hemiptera: Reduviidae), the main vector of Chagas disease in Argentina. However, toxicity effects and resistance have resulted from repeated applications of these insecticides over long periods. The aim of this study was to evaluate the efficacy of three isolates of entomopathogenic nematodes (EPN): Heterorhabditis bacteriophora (RN and SUP strains) and Steinernema feltiae (NEMAPOM), against pyrethroid-resistant and non-resistant T. infestans populations. Survival of pyrethroid-resistant and non-resistant T. infestans nymphs was significantly reduced in those parasitized by EPN strains compared to the controls, reaching values close to 10%, three and six days after exposure to Heterorhabditis and Steinernema, respectively. The lowest survival of T. infestans nymphs resulted from application of H. bacteriophora strains. No significant differences were observed between pyrethroid-resistant and non-resistant T. infestans populations for any of the parameters evaluated. The three strains were able to multiply and emerge as infective juveniles (IJs) from T. infestans cadavers, completing their lifecycle in both pyrethroid-resistant and non-resistant populations, but highest IJ production was observed in H. bacteriophora strains. Future studies should consider the incorporation of drought-tolerant EPN strains, as well as evaluating an adequate release strategy before field imple- mentation of EPNs as biological control agents of T. infestans.
查看更多>>摘要：Understanding important aspects of the adaptation of a biological control agent population to different abiotic conditions (e.g., temperature) is essential to ensure its success once it is released in the field . In this context, we assessed different biological parameters of three Argentinian populations of Pseudapanteles dignus (from Salta, Buenos Aires and Rio Negro provinces), a larval endoparasitoid of the South American tomato pinworm, Tuta absoluta, a key pest of tomato crops worldwide, under various regimes of temperature (25, 28 and 30 degrees C). All local populations of P. dignus showed density-independent parasitism at the temperatures tested , and sex ratios did not deviate from 1:1 except for Salta population at 30 degrees C. Intra and inter-population comparisons revealed differences in pre-imaginal development times according to the temperature regimes. These results may be exploited to improve mass rearing of P. dignus and to implement biological control programs of T. absoluta in Argentina.
查看更多>>摘要：Diaphorina citri (Hemiptera: Liviidae) is an invasive citrus pest that colonizes young flush shoots and spreads huanglongbing, a lethal citrus disease. Effects of D. citri colony size (nymphs per shoot) and instar composition on parasitism rates by the nymphal ectoparasitoid, Tamarixia radiata (Hymenoptera: Eulophidae), were evaluated on residential citrus in South Texas. From 2016 to 17, D. citri colony sizes and apparent parasitism (T. radiata adult emergence) were monitored monthly on grapefruit, lemon, lime, and orange trees at 12 residential sites. In 2019, size and instar composition of colonies and actual parasitism (mummies and nymphs with parasitoid larvae or eggs) were monitored biweekly on citrus trees at a residential park. Psyllid nymphs were found year-round at these sites with highest densities from late summer to fall and lowest densities in winter. Mean apparent parasitism was independent of citrus species and ranged from 23% in April 2016 to 4% in February 2017. Mean actual parasitism ranged from 1.5% in August to 33.4% in November 2019. Because actual parasitism of 3rd or younger instars was very rare, a 'host patch' was defined as the cluster(s) of 4th to 5th instars within a colony infesting a shoot. Based on apparent or actual parasitism, host density was positively related to discovery of D. citri colonies but inversely related to percent parasitism by T. radiata. The inability of T. radiata to achieve high rates of field parasitism under a wide range of host densities could explain, in part, its low impact against D. citri on residential citrus.
Bercovich, Barbara A.Villafane, David L.Bianchi, Julieta S.Taddia, Camila...
11页
查看更多>>摘要：The aim of this work was to analyze Streptomyces eurocidicus as growth promoter for soybean (Glycine max (L.) Merr.) plants and to study the role of antifungal polyene eurocidin produced by this strain on the biocontrol over two soybean phytopathogenic fungi, Macrophomina phaseolina and Diaporthe aspalathi, which are generally controlled by environmentally harmful chemical antifungals and genetic resistance, respectively. In vitro studies confirmed that the eurocidin producer S. eurocidicus inhibited these pathogens as well as several other important phytopathogenic fungi, while non-antagonistic effect on Bradyrhizobium japonicum was observed. Phenotypic characterization of S. eurocidicus strain showed its potential as growth promoter agent, a property probably related with its ability to produce siderophores and 3-indolacetic acid and also to solubilize tricalcium phos-phate. Moreover, the results obtained demonstrate that seeds treatment with S. eurocidicus promotes soybean plants growth and development, either alone or in combination with B. japonicum in vegetative stage and also, enhances seeds produced per plant at crop maturity under greenhouse conditions. Biocontrol experiments using soybean-M. phaseolina and soybean-D. aspalathi pathosystems showed that the polyene-producer S. eurocidicus and a eurocidin non-producer mutant strain protect soybean plants reducing the severity of both diseases. These results suggested that there is/are another mechanism/s for soybean plants protection independent of the polyene antifungal per se. Altogether these results demonstrate that S. eurocidicus is a good biocontrol agent and also a growth and development promoter; and strongly support further research on this field in order to pursue their use to sustainably manage crop diseases while stimulating plant growth.
NSTL
Elsevier