Reducing Pathogen Survival Research Articles

Sporangial responses do not reflect microbial suppression of Phytophthora drechsleri in composted eucalyptus bark mix

When morphology and germination behaviour of sporangia produced by Phytophthora drechsleri were examined in the presence of 262 isolates of fungi and 64 isolates of actinomycetes in sterile, irradiated Eucalyptus bark compost (CEB), seventeen response groups could be distinguished. The sporangial responses considered were combinations of direct and indirect germination, inviable maturenormal and deformed-small sporangia. Each sporangial response group was associated with a range of percentage pathogen survival or infectivtty values. There were no obvious relationships between sporangial response groups and pathogen survival or infectivity on Waratah ( Telopea speciossima). Few actinomycete or fungal intcractants reduced pathogen survival. However. 72 and 60.9% of the fungal and actinomycete populations, respectively, reduced percentage infectivity to ⩽75%. 173 (66%) fungal and 49 (76.5%) actinomycete intcractants caused disease suppression. The results suggest that most of the fungal and actinomycete interactants in the CEB did not suppress the pathogen, but did suppress disease and that P. drechsleri possesses some competitive saprophytic ability.

Application of Trichoderma and Gliocladium in alginate pellets for control of Rhizoctonia damping‐off

Alginate pellets were prepared from wet fermentor biomass of 11 isolates of Trichoderma spp. and Gliocladium virens, with wheat bran as a food base carrier. Pellets with eight of the isolates reduced survival (34‐78%) of Rhizoctonia solani in infested beet seed in soil. Pellets containing a T. harzianum isolate (Th‐58) and a T. hamatum isolate (TRI‐4) were the most effective. All isolates significantly reduced growth of the pathogen from infested beet seed into natural soil. Populations of isolates proliferated in soil to 106−1011 colony‐forming units/g (cfu) from propagules within the pellets. Pellets with TRI‐4 reduced pathogen survival and growth (>70%) in six different soils and were effective against six R. solani isolates in a natural loamy sand. Survival of R. solani in infested beet seed was not reduced when TRI‐4 pellets were added to soil 1‐6 weeks before the pathogen; however, saprophytic growth was prevented. Small amounts of biomass (3.0–7.5 g wet weight) in pellets were as effective as a large amount (300 g) in suppressing the pathogen. The storage of pellets for more than 6 weeks at 5 or 25C reduced their effectiveness against R. solani. Pellets prepared with four and three of the 11 isolates prevented damping‐off of cotton and sugar beet in the greenhouse, respectively.

Reduction of inoculum of Rhizoctonia solani in soil by germlings of Trichoderma hamatum

Three- and 8-day-old inoculum of Trichoderma hamatum (TRI-4), consisting of young, actively-growing hyphae on bran, reduced survival of Rhizoctonia solani in infested beet seed by about 90% during the first week of incubation and prevented growth of the pathogen from beet seed into soil. The 3-day-old inoculum is considered a germling preparation. An older preparation (40-day-old), which did not contain growing hyphae, or conidia on bran (0-day-old) did not reduce survival or growth of R. solani even after 3 weeks of incubation. A 15-day-old preparation reduced survival about 50%. Addition of germlings to soil at a rate of 0.13% reduced pathogen survival and growth as effectively as a 1% rate after 3–6 weeks of incubation. There was nearly complete reduction (>90%) in survival when germlings were added to soil at the same time as seed infested with R. solani or 1 week later; a 50% reduction in survival when added 2 or 4 weeks after R. solani, and no reduction when added to soil 1, 2 or 4 weeks before the pathogen. Saprophytic growth was generally prevented by germlings except if they were added 2 or 4 weeks before the infested beet seed. Isolate TRI-4 rapidly grew from the bran into soil and within 2 days it penetrated and attacked R. solani embedded in beet seed so that pathogen survival dropped to about 20% and the population of TRI-4 proliferated within the seed. Germlings of TRI-4 reduced survival (>90%) and growth (>50%) of several isolates of R. solani in a loamy sand. Survival and growth of R. solani isolate R-23, was reduced more than 90% in seven different soil types within 1 week of incubation. Germlings reduced pathogen survival under all conditions of temperature, moisture and pH studied except under high moisture at 32°C. The greatest reduction (91–100%) was observed at all soil moisture levels at 15° and 23°C and at pH 5.0 and 6.4.

Diagnosis of equipment failures by pattern recognition : L. F. Pau. IEEE Trans. Reliab.R-23, 3, 202 (August 1974)

Three- and 8-day-old inoculum of Trichoderma hamatum (TRI-4), consisting of young, actively-growing hyphae on bran, reduced survival of Rhizoctonia solani in infested beet seed by about 90% during the first week of incubation and prevented growth of the pathogen from beet seed into soil. The 3-day-old inoculum is considered a germling preparation. An older preparation (40-day-old), which did not contain growing hyphae, or conidia on bran (0-day-old) did not reduce survival or growth of R. solani even after 3 weeks of incubation. A 15-day-old preparation reduced survival about 50%. Addition of germlings to soil at a rate of 0.13% reduced pathogen survival and growth as effectively as a 1% rate after 3–6 weeks of incubation. There was nearly complete reduction (>90%) in survival when germlings were added to soil at the same time as seed infested with R. solani or 1 week later; a 50% reduction in survival when added 2 or 4 weeks after R. solani, and no reduction when added to soil 1, 2 or 4 weeks before the pathogen. Saprophytic growth was generally prevented by germlings except if they were added 2 or 4 weeks before the infested beet seed. Isolate TRI-4 rapidly grew from the bran into soil and within 2 days it penetrated and attacked R. solani embedded in beet seed so that pathogen survival dropped to about 20% and the population of TRI-4 proliferated within the seed. Germlings of TRI-4 reduced survival (>90%) and growth (>50%) of several isolates of R. solani in a loamy sand. Survival and growth of R. solani isolate R-23, was reduced more than 90% in seven different soil types within 1 week of incubation. Germlings reduced pathogen survival under all conditions of temperature, moisture and pH studied except under high moisture at 32°C. The greatest reduction (91–100%) was observed at all soil moisture levels at 15° and 23°C and at pH 5.0 and 6.4.