{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/140895"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/140895","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Compost effects on plectosporium blight","abstract":"Plectosporium blight, also known as Plecto, is an emerging pumpkin, zucchini, and squash disease persistent in the eastern United States since the late 1980s. Its pathogen, Plectosporium tabacinum, is a fungal saprophyte capable of surviving in the soil for several years with limited research available on its life cycle. Compost is widely used as a tool to improve soil health with the assumption of preventing or mitigating disease effects, but this is not always the case. Compost is most often characterized as having a suppressive effect; however, in rare instances, it has been found to increase disease. To better understand the mechanisms driving compost effects, this study examines the role of compost source versus microbial activity in P. tabacinum growth in vitro and in vivo. In a laboratory setting, five replicates of plant, animal, vermicompost, and mixed source compost treatments, with and without microbial sterilization, were added to 150 mm x 15 mm petri dishes centrally inoculated with P. tabacinum. After 7 days of incubation, the pathogen growth was measured radially using a spatial divider. Analysis revealed a significant interaction effect between the compost source and microbial activity (P = 0.01). The sterilized animal compost (4.6 ± 0.6, mean ± SE) and unsterilized mixed compost (5.0 ± 0.6, mean ± SE) resulted in significantly decreased growth of P. tabacinum (cm of radial growth) compared to the non-amended control (5.8 ± 0.2, mean ± SE). In contrast, the sterilized mixed compost (6.6 ± 0.6, mean ± SE) significantly increased its growth compared to the control. Each treatment underwent a nutrient and enzyme analysis to provide insight to their varied outcomes. There was a significant relationship between P. tabacinum growth and the enzymatic activity of β-glucosidase (BG) (P < 0.05). These findings suggest that the source material and microbial communities associated with composts both have varying effects of compost on P. tabacinum growth in vitro. Additionally, the enzymatic activity related to the breakdown of cellulose may play a role in the effects of compost on P. tabacinum growth. In an outdoor pot experiment, a compact variety of 'Black Beauty' zucchini (Cucurbita pepo) was transplanted into 24.3-liter pots that were amended with six replicates of sterilized and unsterilized treatments of plant, animal, and worm source composts. After establishing in the treated pots for two weeks, the plants were inoculated with P. tabacinum using a drench method applied to the stems and leaves. Plants were checked weekly for the following five weeks to record crop growth stage, disease severity, fruit production, and week of death. Plectosporium blight disease severity was only significantly affected by compost source in Week 5 (P < 0.001). The animal source compost presented significantly lower disease severity than the plant and worm composts during Week 5 with 30% less symptomatic area; this was most similar to the disease severity of the control. However, all plants regardless of treatment reached total plant death by Week 8. Plectosporium blight limited overall fruit production but did not significantly differ across treatment types. This in vivo study indicates that compost of varying sources and microbial activity had little to no overall effect on the disease plectosporium blight in zucchini.","abstract_html":"Plectosporium blight, also known as Plecto, is an emerging pumpkin, zucchini, and squash disease persistent in the eastern United States since the late 1980s. Its pathogen, Plectosporium tabacinum, is a fungal saprophyte capable of surviving in the soil for several years with limited research available on its life cycle. Compost is widely used as a tool to improve soil health with the assumption of preventing or mitigating disease effects, but this is not always the case. Compost is most often characterized as having a suppressive effect; however, in rare instances, it has been found to increase disease. To better understand the mechanisms driving compost effects, this study examines the role of compost source versus microbial activity in P. tabacinum growth in vitro and in vivo. In a laboratory setting, five replicates of plant, animal, vermicompost, and mixed source compost treatments, with and without microbial sterilization, were added to 150 mm x 15 mm petri dishes centrally inoculated with P. tabacinum. After 7 days of incubation, the pathogen growth was measured radially using a spatial divider. Analysis revealed a significant interaction effect between the compost source and microbial activity (P = 0.01). The sterilized animal compost (4.6 ± 0.6, mean ± SE) and unsterilized mixed compost (5.0 ± 0.6, mean ± SE) resulted in significantly decreased growth of P. tabacinum (cm of radial growth) compared to the non-amended control (5.8 ± 0.2, mean ± SE). In contrast, the sterilized mixed compost (6.6 ± 0.6, mean ± SE) significantly increased its growth compared to the control. Each treatment underwent a nutrient and enzyme analysis to provide insight to their varied outcomes. There was a significant relationship between P. tabacinum growth and the enzymatic activity of β-glucosidase (BG) (P &lt; 0.05). These findings suggest that the source material and microbial communities associated with composts both have varying effects of compost on P. tabacinum growth in vitro. Additionally, the enzymatic activity related to the breakdown of cellulose may play a role in the effects of compost on P. tabacinum growth. In an outdoor pot experiment, a compact variety of &#x27;Black Beauty&#x27; zucchini (Cucurbita pepo) was transplanted into 24.3-liter pots that were amended with six replicates of sterilized and unsterilized treatments of plant, animal, and worm source composts. After establishing in the treated pots for two weeks, the plants were inoculated with P. tabacinum using a drench method applied to the stems and leaves. Plants were checked weekly for the following five weeks to record crop growth stage, disease severity, fruit production, and week of death. Plectosporium blight disease severity was only significantly affected by compost source in Week 5 (P &lt; 0.001). The animal source compost presented significantly lower disease severity than the plant and worm composts during Week 5 with 30% less symptomatic area; this was most similar to the disease severity of the control. However, all plants regardless of treatment reached total plant death by Week 8. Plectosporium blight limited overall fruit production but did not significantly differ across treatment types. This in vivo study indicates that compost of varying sources and microbial activity had little to no overall effect on the disease plectosporium blight in zucchini.","abstract_has_math":false,"creators":["Gratta, Samantha Adelia"],"institution":"Virginia Tech","degree_name":"Master of Science in Life Sciences","degree_level":"masters","degree_discipline":"Plant Pathology, Physiology and Weed Science","degree_department":"Plant Pathology, Physiology and Weed Science","school":null,"contributors":[],"advisors":[],"committee_chairs":["Jernigan, Ashley","Stallknecht, Eric J."],"committee_members":["Rideout, Steven L.","Gan, Huijie"],"year":2026,"date_issued":"2026-01-20","date_published":"2026-01-20","updated_at":"2026-07-22T22:19:47Z","subjects":["Plectosporium tabacinum","plectosporium blight","compost","microbial activity","zucchini"],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45374"],"render_values":[{"text":"vt_gsexam:45374","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/140895","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Jernigan, Ashley","Stallknecht, Eric J."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Rideout, Steven L.","Gan, Huijie"]},{"key":"dc:contributor.department","label":"Department","values":["Plant Pathology, Physiology and Weed Science"]},{"key":"dc:creator","label":"Author","values":["Gratta, Samantha Adelia"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-01-21T09:00:10Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-01-21T09:00:10Z"]},{"key":"dc:date.issued","label":"Date","values":["2026-01-20"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Plant Pathology, Physiology and Weed Science"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science in Life Sciences"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Plectosporium tabacinum","plectosporium blight","compost","microbial activity","zucchini"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45374"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/140895"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Plectosporium blight, also known as Plecto, is an emerging pumpkin, zucchini, and squash disease persistent in the eastern United States since the late 1980s. Its pathogen, Plectosporium tabacinum, is a fungal saprophyte capable of surviving in the soil for several years with limited research available on its life cycle. Compost is widely used as a tool to improve soil health with the assumption of preventing or mitigating disease effects, but this is not always the case. Compost is most often characterized as having a suppressive effect; however, in rare instances, it has been found to increase disease. To better understand the mechanisms driving compost effects, this study examines the role of compost source versus microbial activity in P. tabacinum growth in vitro and in vivo. In a laboratory setting, five replicates of plant, animal, vermicompost, and mixed source compost treatments, with and without microbial sterilization, were added to 150 mm x 15 mm petri dishes centrally inoculated with P. tabacinum. After 7 days of incubation, the pathogen growth was measured radially using a spatial divider. Analysis revealed a significant interaction effect between the compost source and microbial activity (P = 0.01). The sterilized animal compost (4.6 ± 0.6, mean ± SE) and unsterilized mixed compost (5.0 ± 0.6, mean ± SE) resulted in significantly decreased growth of P. tabacinum (cm of radial growth) compared to the non-amended control (5.8 ± 0.2, mean ± SE). In contrast, the sterilized mixed compost (6.6 ± 0.6, mean ± SE) significantly increased its growth compared to the control. Each treatment underwent a nutrient and enzyme analysis to provide insight to their varied outcomes. There was a significant relationship between P. tabacinum growth and the enzymatic activity of β-glucosidase (BG) (P < 0.05). These findings suggest that the source material and microbial communities associated with composts both have varying effects of compost on P. tabacinum growth in vitro. Additionally, the enzymatic activity related to the breakdown of cellulose may play a role in the effects of compost on P. tabacinum growth. In an outdoor pot experiment, a compact variety of 'Black Beauty' zucchini (Cucurbita pepo) was transplanted into 24.3-liter pots that were amended with six replicates of sterilized and unsterilized treatments of plant, animal, and worm source composts. After establishing in the treated pots for two weeks, the plants were inoculated with P. tabacinum using a drench method applied to the stems and leaves. Plants were checked weekly for the following five weeks to record crop growth stage, disease severity, fruit production, and week of death. Plectosporium blight disease severity was only significantly affected by compost source in Week 5 (P < 0.001). The animal source compost presented significantly lower disease severity than the plant and worm composts during Week 5 with 30% less symptomatic area; this was most similar to the disease severity of the control. However, all plants regardless of treatment reached total plant death by Week 8. Plectosporium blight limited overall fruit production but did not significantly differ across treatment types. This in vivo study indicates that compost of varying sources and microbial activity had little to no overall effect on the disease plectosporium blight in zucchini."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["This thesis investigates compost effects on plectosporium blight in a laboratory setting and an outdoor pot experiment. The fungal plant pathogen, Plectosporium tabacinum, causes the disease plectosporium blight which considerably reduces pumpkin, squash, and zucchini yields across the eastern United States. Compost is widely used as a tool to prevent or improve disease outcomes, though it has mixed effects. Compost may increase or decrease the pathogen depending on a variety of factors from its beneficial microorganisms to its nutrient content. To better understand what drives compost effects, this study examines the role of compost source versus microbial activity in compost effects on plectosporium blight. In a laboratory setting, composts made from plant, animal, worm, and mixed sources, with and without the presence of microorganisms, were placed in a petri dish with P. tabacinum. After incubating together for one week, the growth of the pathogen was measured by dividing the plate into sections to see how far the plectosporium spread from its starting point. Our results found that the source and presence of microorganisms associated with composts both had varying effects of compost on P. tabacinum growth. Each compost underwent a nutrient and enzyme analysis to provide insight to their varied outcomes. This analysis suggested that the enzymatic activity related to the breakdown of cellulose may play a role in the effects of compost on P. tabacinum growth. In an outdoor pot experiment, zucchini was grown in large pots containing treatments of composts made from plant, animal, and worm sources, with and without the presence of microorganisms. The pathogen P. tabacinum was then introduced to the plants through application to the stems and leaves. Plants were checked each week for stem, leaf, and fruit growth, and disease severity until total plant death. Plectosporium blight disease severity was found to be significantly affected by compost source in terms of week. The no compost added control and animal source compost presented lower disease severity than the plant and worm composts during several of the weeks; however, all plants regardless of treatment reached total plant death by Week 8. This study indicates that compost of varying sources and microorganism activity had little to no overall effect on the disease plectosporium blight in zucchini."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science in Life Sciences"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Compost effects on plectosporium blight"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Jernigan, Ashley","Stallknecht, Eric J."],"dc:contributor.committeemember":["Rideout, Steven L.","Gan, Huijie"],"dc:contributor.department":["Plant Pathology, Physiology and Weed Science"],"dc:creator":["Gratta, Samantha Adelia"],"dc:date.accessioned":["2026-01-21T09:00:10Z"],"dc:date.available":["2026-01-21T09:00:10Z"],"dc:date.issued":["2026-01-20"],"dc:description.abstract":["Plectosporium blight, also known as Plecto, is an emerging pumpkin, zucchini, and squash disease persistent in the eastern United States since the late 1980s. Its pathogen, Plectosporium tabacinum, is a fungal saprophyte capable of surviving in the soil for several years with limited research available on its life cycle. Compost is widely used as a tool to improve soil health with the assumption of preventing or mitigating disease effects, but this is not always the case. Compost is most often characterized as having a suppressive effect; however, in rare instances, it has been found to increase disease. To better understand the mechanisms driving compost effects, this study examines the role of compost source versus microbial activity in P. tabacinum growth in vitro and in vivo. In a laboratory setting, five replicates of plant, animal, vermicompost, and mixed source compost treatments, with and without microbial sterilization, were added to 150 mm x 15 mm petri dishes centrally inoculated with P. tabacinum. After 7 days of incubation, the pathogen growth was measured radially using a spatial divider. Analysis revealed a significant interaction effect between the compost source and microbial activity (P = 0.01). The sterilized animal compost (4.6 ± 0.6, mean ± SE) and unsterilized mixed compost (5.0 ± 0.6, mean ± SE) resulted in significantly decreased growth of P. tabacinum (cm of radial growth) compared to the non-amended control (5.8 ± 0.2, mean ± SE). In contrast, the sterilized mixed compost (6.6 ± 0.6, mean ± SE) significantly increased its growth compared to the control. Each treatment underwent a nutrient and enzyme analysis to provide insight to their varied outcomes. There was a significant relationship between P. tabacinum growth and the enzymatic activity of β-glucosidase (BG) (P < 0.05). These findings suggest that the source material and microbial communities associated with composts both have varying effects of compost on P. tabacinum growth in vitro. Additionally, the enzymatic activity related to the breakdown of cellulose may play a role in the effects of compost on P. tabacinum growth. In an outdoor pot experiment, a compact variety of 'Black Beauty' zucchini (Cucurbita pepo) was transplanted into 24.3-liter pots that were amended with six replicates of sterilized and unsterilized treatments of plant, animal, and worm source composts. After establishing in the treated pots for two weeks, the plants were inoculated with P. tabacinum using a drench method applied to the stems and leaves. Plants were checked weekly for the following five weeks to record crop growth stage, disease severity, fruit production, and week of death. Plectosporium blight disease severity was only significantly affected by compost source in Week 5 (P < 0.001). The animal source compost presented significantly lower disease severity than the plant and worm composts during Week 5 with 30% less symptomatic area; this was most similar to the disease severity of the control. However, all plants regardless of treatment reached total plant death by Week 8. Plectosporium blight limited overall fruit production but did not significantly differ across treatment types. This in vivo study indicates that compost of varying sources and microbial activity had little to no overall effect on the disease plectosporium blight in zucchini."],"dc:description.abstractgeneral":["This thesis investigates compost effects on plectosporium blight in a laboratory setting and an outdoor pot experiment. The fungal plant pathogen, Plectosporium tabacinum, causes the disease plectosporium blight which considerably reduces pumpkin, squash, and zucchini yields across the eastern United States. Compost is widely used as a tool to prevent or improve disease outcomes, though it has mixed effects. Compost may increase or decrease the pathogen depending on a variety of factors from its beneficial microorganisms to its nutrient content. To better understand what drives compost effects, this study examines the role of compost source versus microbial activity in compost effects on plectosporium blight. In a laboratory setting, composts made from plant, animal, worm, and mixed sources, with and without the presence of microorganisms, were placed in a petri dish with P. tabacinum. After incubating together for one week, the growth of the pathogen was measured by dividing the plate into sections to see how far the plectosporium spread from its starting point. Our results found that the source and presence of microorganisms associated with composts both had varying effects of compost on P. tabacinum growth. Each compost underwent a nutrient and enzyme analysis to provide insight to their varied outcomes. This analysis suggested that the enzymatic activity related to the breakdown of cellulose may play a role in the effects of compost on P. tabacinum growth. In an outdoor pot experiment, zucchini was grown in large pots containing treatments of composts made from plant, animal, and worm sources, with and without the presence of microorganisms. The pathogen P. tabacinum was then introduced to the plants through application to the stems and leaves. Plants were checked each week for stem, leaf, and fruit growth, and disease severity until total plant death. Plectosporium blight disease severity was found to be significantly affected by compost source in terms of week. The no compost added control and animal source compost presented lower disease severity than the plant and worm composts during several of the weeks; however, all plants regardless of treatment reached total plant death by Week 8. This study indicates that compost of varying sources and microorganism activity had little to no overall effect on the disease plectosporium blight in zucchini."],"dc:description.degree":["Master of Science in Life Sciences"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:45374"],"dc:identifier.uri":["https://hdl.handle.net/10919/140895"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Plectosporium tabacinum","plectosporium blight","compost","microbial activity","zucchini"],"dc:title":["Compost effects on plectosporium blight"],"dc:type":["Thesis"],"thesis:degree_discipline":["Plant Pathology, Physiology and Weed Science"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science in Life Sciences"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:47Z"}