Efficacy and physical mode of action of fungicides against leather rot of strawberry and sensitivity of phytophthora cactorum isolates to azoxystrobin
Notice bibliographique
Résumé
Efficacy and physical mode of action of azoxystrobin, pyraclostrobin, mefenoxam, and phosphorous acid (potassium phosphite) for control of strawberry leather rot, caused by Phytophthora cactorum, was evaluated on a commercial farm and under greenhouse conditions.In addition, the distribution of the sensitivity of P. cactorum isolates to azoxystrobin and pyraclostrobin was determined under in vitro conditions.In field trials, foliar sprays of azoxystrobin, pyraclostrobin, and phosphorous acid were applied weekly from bloom through harvest, and mefenoxam was applied twice as a soil drench at early plant growth and at fruit set.All fungicide treatments had significantly less leather rot than the untreated control and there were no significant differences in leather rot incidence among any fungicide treatments during both years of testing.Results from these studies indicate that azoxystrobin and pyraclostrobin provide excellent control of strawberry leather rot.To determine the physical mode of action of the previously mentioned fungicides, pre-and post-infection activity was determined under greenhouse conditions.Strawberry plants ('Honeoye') and attached fruits at the green to white stage of development were sprayed with fungicides at 2, 4 and 7 days before inoculation with a zoospore suspension or 13, 24, 36, and 48 hours after inoculation.Disease incidence was recorded at 6 days after inoculation.Azoxystrobin and pyraclostrobin provided protectant activity for up to 7 days, but only slight curative activity when applied 13 hours after iii inoculation.Phosphorous acid and mefenoxam also provided protection for up to 7 days and curative activity of at least 36 hours.No significant differences in protectant activity between tested fungicides were observed.Sensitivity distributions of P. cactorum isolates, causing crown rot and leather rot, to azoxystrobin were determined based on mycelial growth and zoospore germination.Radial growth of mycelia on lima bean agar amended with 0.001, 0.01, 0.1, 1.0, 10 and 30 μg/ml of azoxystrobin plus 100 μg/ml of salicylhydroxamic acid (SHAM) was measured after 6 days.Effects on zoospore germination were evaluated in aqueous solutions of 0.005, 0.01, 0.05, 0.1, 0.5, and 1.0 μg/ml of azoxystrobin after 4 h of incubation in 96-well microtiter plates.Effective dose (ED 50 ) for mycelial growth ranged from 0.16 to 12.52 μg/ml for leather rot isolates, and 0.1 to 15 μg/ml for crown rot isolates.The Kolmogorov-Smirnov test showed significant differences (P<0.001) between the two distributions.Estimated ED 50 values for zoospores ranged from 0.01 to 0.24 μg/ml.Sensitivities of mycelia and zoospores were not strongly correlated (r=0.31).Additional experiments with pyraclostrobin showed that mycelia and zoospores were more sensitive to pyraclostrobin than to azoxystrobin.Azoxystrobin and pyraclostrobin sensitivities were moderately but significantly correlated (r=0.60).The sensitivity distribution obtained in these studies could be used as a baseline sensitivity for monitoring fungicide resistance development in P.cactorum to these fungicides.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».