Abstract
Pythium root rot ( Pythium sp.) is ubiquitous in Michigan greenhouses that produce herbaceous ornamentals, an industry worth $393 million in the state. Disease symptoms include stunting, flowering delay, root rot, and death. Fungicides that are highly effective against pythium root rot are limited, and pathogen resistance has been documented. The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole and to determine the influence of pH and etridiazole on Pythium mycelial growth and asexual reproduction. Isolates were tested in vitro for sensitivity to etridiazole by growing the pathogen on amended V8-agar plates sealed in plastic containers to minimize fungicide loss from the vapor phase. The majority of isolates of all three species were sensitive to the fungicide with EC 50 (effective concentration resulting in 50% inhibition of linear growth) values ranging from 0.10 to 5.03 μg·mL −1 . Two isolates of P. irregulare had an EC 90 (effective concentration resulting in 90% inhibition of linear growth) value >80 μg·mL −1 . The acidity of the medium influenced the ability of etridiazole to inhibit Pythium mycelial growth and asexual reproduction. Agar plates amended with 1 μg·mL −1 etridiazole and adjusted to pH 4.5 limited the mycelial growth of two P. aphanidermatum isolates and two P. irregulare isolates by 90% and 56%, respectively, compared with amended agar at pH 6.5. Sporangial formation by P. aphanidermatum was less frequent on mycelial disks incubated in etridiazole-amended sterile distilled water (SDW) at pH 4.5 than pH 6.5 ( P < 0.05). P. aphanidermatum zoospore cyst germination was less sensitive to etridiazole than sporangia or mycelial growth; however, the influence of pH and fungicide on cyst germination was significant ( P < 0.01). At 250 μg·mL −1 etridiazole and solution pH 4.5, zoospore cyst germination was inhibited 99.9% compared with 94.2% at pH 6.5. In a greenhouse experiment, disease symptoms were observed on ‘Pinto White’ geranium ( Pelargonium × hortorum ) in a potting medium infested with P. aphanidermatum and adjusted to pH 4.5 or 6.5; however, plant health and fresh weight were greater in low pH potting medium. Etridiazole, applied as a drench at transplant, did not improve control of root rot for plants grown at low pH ( P > 0.05). Fresh weight of plants grown in infested potting medium adjusted to pH 4.5 and amended with a single drench of etridiazole (100 μg·mL −1 ) was reduced 20%, statistically similar to the untreated control. Adjusting the acidity of irrigation water at the time of etridiazole application in ebb and flow and flood floor production systems could be beneficial in pythium root rot management of certain ornamental crops if plants have tolerance to low pH.
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Claims 14
Claim · model-written summary
The majority of Pythium isolates were sensitive to etridiazole, with EC50 values from 0.10 to 5.03 μg·mL −1.
- Taxon
- herbaceous greenhouse ornamentalse1
- Outcome
- sensitive to the fungicidee2
- Value
- 0.10 to 5.03 μg·mL −1e2
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PythiumNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
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Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e2“The majority of isolates of all three species were sensitive to the fungicide with EC 50 (effective concentration resulting in 50% inhibition of linear growth) values ranging from 0.10 to 5.03 μg·mL −1”
Claim · model-written summary
Two P. irregulare isolates had an EC90 above 80 μg·mL −1, indicating reduced sensitivity.
- Taxon
- herbaceous greenhouse ornamentalse1
- Interactor
- P. irregulareGlobisporangium irregularee3pathogen
- Outcome
- EC 90e3
- Value
- >80 μg·mL −1e3
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e3“Two isolates of P. irregulare had an EC 90 (effective concentration resulting in 90% inhibition of linear growth) value >80 μg·mL −1”
Claim · model-written summary
The acidity of the medium influenced the ability of etridiazole to inhibit Pythium mycelial growth and asexual reproduction.
- Taxon
- herbaceous greenhouse ornamentalse1
- Treatment
- The acidity of the mediume4
- Outcome
- mycelial growth and asexual reproductione4
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e4“The acidity of the medium influenced the ability of etridiazole to inhibit Pythium mycelial growth and asexual reproduction”
Claim · model-written summary
At pH 4.5 with 1 μg·mL −1 etridiazole, mycelial growth of two P. aphanidermatum isolates was limited by 90% compared with pH 6.5.
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e5“Agar plates amended with 1 μg·mL −1 etridiazole and adjusted to pH 4.5 limited the mycelial growth of two P. aphanidermatum isolates and two P. irregulare isolates by 90% and 56%, respectively, compared with amended agar at pH 6.5”
Claim · model-written summary
At pH 4.5 with 1 μg·mL −1 etridiazole, mycelial growth of two P. irregulare isolates was limited by 56% compared with pH 6.5.
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e5“Agar plates amended with 1 μg·mL −1 etridiazole and adjusted to pH 4.5 limited the mycelial growth of two P. aphanidermatum isolates and two P. irregulare isolates by 90% and 56%, respectively, compared with amended agar at pH 6.5”
Claim · model-written summary
Sporangial formation by P. aphanidermatum was less frequent in etridiazole-amended water at pH 4.5 than at pH 6.5.
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e6“Sporangial formation by P. aphanidermatum was less frequent on mycelial disks incubated in etridiazole-amended sterile distilled water (SDW) at pH 4.5 than pH 6.5”
Claim · model-written summary
Zoospore cyst germination of P. aphanidermatum was less sensitive to etridiazole than sporangia or mycelial growth.
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e7“P. aphanidermatum zoospore cyst germination was less sensitive to etridiazole than sporangia or mycelial growth”
Claim · model-written summary
The influence of pH and fungicide on cyst germination was significant.
Not reportedDirection
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e2“the influence of pH and fungicide on cyst germination was significant”
Claim · model-written summary
At 250 μg·mL −1 etridiazole and pH 4.5, zoospore cyst germination was inhibited by 99.9%, compared with 94.2% at pH 6.5.
Verbatim
e1“The objectives of this study were to determine the sensitivity of Pythium irregulare , Pythium ultimum , and Pythium aphanidermatum isolates from symptomatic herbaceous greenhouse ornamentals to the fungicide etridiazole”
e2“At 250 μg·mL −1 etridiazole and solution pH 4.5, zoospore cyst germination was inhibited 99.9% compared with 94.2% at pH 6.5”
Claim · model-written summary
Disease symptoms were observed on geranium in a greenhouse experiment in potting medium infested with P. aphanidermatum at pH 4.5 or 6.5.
- Treatment
- adjusted to pH 4.5 or 6.5e2
- Interactor
- P. aphanidermatumPythium aphanidermatume2pathogen
- Outcome
- disease symptomse2
- Setting
- greenhouse experimente2
GeraniumNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“In a greenhouse experiment, disease symptoms were observed on ‘Pinto White’ geranium ( Pelargonium × hortorum ) in a potting medium infested with P. aphanidermatum and adjusted to pH 4.5 or 6.5”
Claim · model-written summary
Plant health and fresh weight were greater in low pH potting medium than in the higher pH medium.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“In a greenhouse experiment, disease symptoms were observed on ‘Pinto White’ geranium ( Pelargonium × hortorum ) in a potting medium infested with P. aphanidermatum and adjusted to pH 4.5 or 6.5”
e3“however, plant health and fresh weight were greater in low pH potting medium”
Claim · model-written summary
Etridiazole applied as a drench at transplant did not improve root rot control for geranium grown at low pH.
- Treatment
- Etridiazole, applied as a drench at transplante3
- Outcome
- control of root rote3
- Direction
- did not improvee3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“In a greenhouse experiment, disease symptoms were observed on ‘Pinto White’ geranium ( Pelargonium × hortorum ) in a potting medium infested with P. aphanidermatum and adjusted to pH 4.5 or 6.5”
e3“Etridiazole, applied as a drench at transplant, did not improve control of root rot for plants grown at low pH”
Claim · model-written summary
Fresh weight of geranium grown at pH 4.5 with a single etridiazole drench was reduced 20%, statistically similar to the untreated control.
- Treatment
- single drench of etridiazole (100 μg·mL −1 )e3
- Outcome
- Fresh weighte3
- Direction
- reducede3
- Value
- 20%e3
- Comparator
- untreated controle3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“In a greenhouse experiment, disease symptoms were observed on ‘Pinto White’ geranium ( Pelargonium × hortorum ) in a potting medium infested with P. aphanidermatum and adjusted to pH 4.5 or 6.5”
e3“Fresh weight of plants grown in infested potting medium adjusted to pH 4.5 and amended with a single drench of etridiazole (100 μg·mL −1 ) was reduced 20%, statistically similar to the untreated control”
Claim · model-written summary
Adjusting irrigation water acidity at etridiazole application could be beneficial for pythium root rot management in certain ornamental crops if plants tolerate low pH.
Verbatim
e2“Adjusting the acidity of irrigation water at the time of etridiazole application in ebb and flow and flood floor production systems could be beneficial in pythium root rot management of certain ornamental crops if plants have tolerance to low pH”
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See all 13 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.