Factors influencing pathogenicity ofFusarium tumidumon gorse (Ulex europaeus) (original) (raw)
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Using insects as potential vectors of Fusarium tumidum to control gorse
New Zealand Entomologist, 2011
The adult light brown apple moth Epiphyas postvittana Walker (Lepidoptera: Tortricidae), gorse seed weevil Apion ulicis Förster, (Coleoptera: Apionidae), gorse pod moth Cydia ulicetana Denis and Schiffermüller (Lepidoptera: Tortricidae) and gorse thrips Sericothrips staphylinus Haliday (Thysanoptera: Thripidae) were assessed for their ability to carry and deposit the conidia of a plant pathogenic fungus Fusarium tumidum Sherb. on agar plates in laboratory experiments. Epiphyas postvittana, the largest insect species studied, carried and deposited the highest number of F. tumidum conidia. The number of colony forming units recovered from all insect species after exposing them to F. tumidum sporulating cultures for 24 h, declined with time. In subsequent transmission experiments using only E. postvittana, each insect was loaded with 5,000 conidia of F. tumidum and caged together with potted healthy gorse (ulex europaeus L.) at eight insects per plant. The insects deposited 310 conidia per plant on average but neither infection nor plant growth effects resulted. Only directly inoculated plants became infected and were significantly shorter with 42% reduction in fresh shoot weight compared with the control treatment. Epiphyas postvittana on its own did not cause any significant plant damage and did not enhance F. tumidum infection. The insect did not spread the conidia from diseased to healthy plants. The results showed that insects are unlikely to be effective vectors in a 'lure-load-infect' approach for biological control of gorse using F. tumidum.
The overall objective of this study was to test the hypothesis that insects can vector F. tumidum conidia to infect gorse plants with the aim of developing an alternative approach to mycoherbicide delivery to control weeds. Four potential insect species (Apion ulicis, Cydia ulicetana, Epiphyas postvittana and Sericothrips staphylinus) were assessed for their ability to vector F. tumidum conidia. To achieve this, the external microflora (bacteria and fungi) and the size and location of fungal spores on the cuticle of these insect species were determined. In addition, the ability of the insects to pick up and deposit F. tumidum conidia on agar was studied. Based on the results from these experiments, E. postvittana was selected for more detailed experiments to determine transmission of F. tumidum to infect potted gorse plants. The factors promoting pathogenicity of F. tumidum against gorse and the pathogen loading required to infect and kill the weed were also determined. The external...
New Phytologist, 1995
The development of uredinia of Uromyces rumicis (Schum.) Wint. was studied on Rumex crispus L. and R. obtusifolius L. plants inoculated in the laboratory. Fewer uredinia developed on leaves injured by simulated insect herbivory, those fed upon by Gastrophysa viridula Degeer (Coleoptera: Chrysomelidae), and young, incompletely expanded leaves, than on uninjured, fully expanded control leaves. The effect of simulated herbivory and leaf age on the process of U. rumicis infection was investigated using Calcofluor staining and epifluorescence microscopy. Simulated insect herbivory reduced significantly the proportion of sporelings producing appressoria and the proportion of sporelings with appressoria that entered the substomatal cavity. In R. obtusifolius, leaf injury also reduced the proportion of penetration hyphae that formed substomatal vesicles. The proportion of sporelings that produced intercellular hyphae in injured leaves was reduced by 58 % in R. crispus and 89 % in R. obtusifolius. G. viridula feeding induced similar resistance in R. obtusifolius leaves.Simulated insect herbivory reduced both uredinial density and the area occupied by intercellular hyphae by between 65% and 89%. Injury had a greater effect than leaf age on sporelings in the pre-haustorial stages of development. However, the total area occupied by intercellular hyphae in young leaves was reduced by between 42% and 78% compared to mature leaves, owing to a lower uredinial density and, in R. obtusifolius, also to a significant reduction in the size of individual uredinia.
Susceptibility of Several Northeastern Conifers to Fusarium circinatum and Strategies for Biocontrol
Forests
Fusarium circinatum, the causal of pine pitch canker disease (PPC), is now considered among the most important pathogens of Pinaceae in the world. Although in Europe PPC is only established in the Iberian Peninsula, the potential endangered areas cover over 10 million hectares under the current host distribution and climatic conditions. It is therefore a priority to test the susceptibility of those species and their provenances, within Central and Northern Europe and find biological control agents (BCAs) against the disease. In this study, the susceptibility of Pinus sylvestris, P. mugo and Picea abies Romanian provenances to F. circinatum was tested using three inoculum doses. In parallel, the potential use of Trichoderma atroviride and Trichoderma viride as BCAs against F. circinatum was also tested. This study has demonstrated, for the first time, the susceptibility of P. mugo to F. circinatum. Likewise, the susceptibility of P. abies was also confirmed. The fact that the Romanian provenance of P. sylvestris has not been susceptible to F. circinatum suggests genetic resistance as a potential tool to manage the disease. This, together with the apparent effectiveness of Trichoderma species as BCAs, seems to indicate that an integrated management of the disease might be feasible.
Forest Research Papers, 2014
Achieving high quality propagative material is difficult today due to the limited number of pesticides recommended for use. Simultaneously, EU regulations on Integrated Pest Management (IPM) in forest nurseries came into a force, requiring a search for alternative plant protection methods that are safe for humans, animals and the environment. In this paper, we present the possibilities of using bio-fungicides against diseases in forest nurseries, their mechanisms of action, as well as the direction of their development (according to IPM rules). We reviewed the results achieved by different research teams presenting the possibilities and trends in combatting Oomycetes and Fusarium spp. pathogens currently having the most important economic impact.
Experiments were conducted to evaluate various formulations and application methods of the fungus Fusarium solani f. sp. cucurbitae (FSC)for controlling Texas gourd (Cucurbita pepo var. texana) in cotton. In greenhouse tests, Texas gourd was controlled 93% and 96%, respectively, with pre-emergence applications of FSC-infested cornmeal/sand medium (CMS) and FSC-wheat flour/kaolin (‘Pesta’) granules. Post-emergence applications of CMS or ‘Pesta’ granular formulations were less effective overall. However, >90% control of Texas gourd was achieved with post-emergence applications of FSC spores formulated in an emulsion consisting of 25% unrefined corn oil and 0.2% Silwet L-77 surfactant. Dew was not required to achieve optimal levels of weed control with either the pre-emergence granular formulations or with post-emergence corn oil/surfactant applications. In field tests, pre-emergence applications of FSC-infested CMS and FSC-‘Pesta’ granules controlled 90-94% of the weeds. Post-emergence applications of FSC formulated in corn oil/surfactant were equally efficacious in controlling Texas gourd in cotton. No damage to cotton was observed.
Journal of Invertebrate Pathology, 2007
Adult female western flower thrips (Frankliniella occidentalis) were exposed 12-24 h to bean (Phaseolus vulgaris) and impatiens (Impatiens wallerana) leaf disks treated with Beauveria bassiana conidia and then transferred to clean bean or impatiens at various times posttreatment. Significantly greater levels of fungal infection were observed when thrips were treated on bean versus impatiens, but exposure to impatiens following treatment had no effect on fungal infection (percent mortality). This result, combined with observations of no inhibition of germination of conidia exposed to intact or macerated impatiens foliage, indicated that the negative effect of the impatiens host plant was not due to plant chemical compounds (antibiosis). Further observations revealed that insects acquired (picked-up) 75% more conidia from treated bean disks than from treated impatiens disks. This difference in dose acquisition was determined to account for the observed difference in percent mortality (15%) following treatment on the two host plants. Median lethal doses (LD 50 ) of B. bassiana were not significantly different on the two host plants, but median lethal concentrations were nearly 7-fold greater on impatiens. This difference was explained by disproportionate rates of conidial acquisition at measured rates of conidial deposition (an inverse relationship was observed between application rate expressed as conidia/mm 2 and the number of conidia acquired). The mechanism underlying the differential rates of conidial acquisition from bean versus impatiens was not determined.
Susceptibility of grapevine tissues to Neofusicoccum luteum conidial infection
Plant Pathology, 2012
This study investigated the ability of Neofusicoccum luteum to infect wounded shoots, trunks, pruned cane ends, leaf surfaces, buds, berries and roots, and its further progression into stem tissues. All tissue types were susceptible to infection except roots, with highest incidences in trunks (100%), cane ends (100%), shoots (92%) and buds (88%), indicating that in New Zealand, N. luteum is primarily a trunk and shoot pathogen. In trunks, there were no external symptoms, although N. luteum could be reisolated from 60 to 70 cm acropetally from the inoculation site after 4 months, by which time the pathogen had progressed into side shoots which became necrotic. Wounded and non-wounded buds became infected; most were killed, with basipetal progression of the pathogen into the supporting shoots. Berries wounded and inoculated at the pre-bunch closure stage were susceptible to N. luteum infection, with isolation incidence increasing over the season and peaking at harvest, when infected berries became mummified and produced pycnidia with many conidia. The pathogen was also able to progress from berries into bunch stems and supporting canes. Results from this research have indicated that N. luteum infection can occur in all aerial grapevine tissues and progress to young stem tissues where it causes wood necrosis. Growers should remove mummified berries from vineyard trash to ensure that pruning and trimming times do not coincide with rainy periods when conidia are released and dispersed. Furthermore, the susceptibility of buds to N. luteum infection indicates the need for fungicide sprays before budburst in spring.
2008
Twenty four gorse (Ulex europaeus L.) bushes each about 1 m tall in a grazed hill pasture in Canterbury, New Zealand, were cut to near ground level in May 2005 before applying three treatments to determine if the stumps could be artificially infected with the fungus Chondrostereum purpureum (Pers.) Pouzar. The stumps of eight of the plants were treated with the mycelium of the fungus on agar, a further eight were treated with mycelium formulated as a slurry, and the remaining eight plants were left untreated. One year after treatment, fruiting bodies of the fungus (basidiocarps) were present in large numbers on 15 of the 16 treated stumps. Seventeen months after treatment (November 2006), half of the C. purpureum-treated stumps were dead, with an overall reduction in the volume of regenerating shoots of 64% as compared to the untreated bushes. These results confirm that C. purpureum has potential as a biological control agent for gorse. Keywords Scrub-weed control, biological weed control, mycoherbicide.