Research Topics, Results and Reports
Replicated experiments have been conducted since 2010 under field conditions at the Cornell University research facility on Long Island. Plots were single beds with one or two staggered rows of basil at 9-inch plant spacing. Naturally-occurring inoculum was relied on. Incidence of affected leaves (percent leaves with sporulation of the pathogen visible on the underside) was assessed rather than severity because any amount of symptoms renders a leaf unmarketable. Severity on affected leaves was usually lower for fungicide-treated plants and resistant varieties compared to controls.
Topics on this page:
- Fungicide Evaluations
- Fungicide Evaluations – Conventional Products
- Fungicide Evaluations – Organic Products
- Plant Resistance Evaluations – Commercial Varieties, Experimental Varieties, and Breeding Lines
- First observations of basil and cucumber downy mildews at LIHREC
- Extension & Research Presentations
See also:
Fungicide Evaluations
Fungicides were applied with a backpack sprayer beginning before or after symptoms were found in the field, which included basil planted before the experiments to serve as a spreader row. A boom with a single (TJ60-4004EVS) nozzle delivering spray to the top of plants was used in 2010 and 2011. Starting in 2012, this boom was used for the first applications until basil plants were large enough to use a boom with two drop nozzles directed to the side of plants as well as a nozzle delivering spray over the top of the plant. This boom was used to improve coverage achieved with a single nozzle directed to the top of plants. Most fungicide treatments were applied on a weekly schedule. Percent affected leaves (with sporulation of the pathogen visible on the underside) was assessed rather than severity (except in 2010) because any amount of symptoms renders a leaf unmarketable.
Fungicide Evaluations – Conventional Products
When tested singly, the most effective fungicides in the 2013 experiment were Zampro*, Revus, Orondis (pka Zorvec)*, and Ranman (*not registered yet). ProPhyt was effective in 2013 but not 2012 when another phosphorous acid fungicide, K-Phite, also was ineffective. Presidio was ineffective. Only Orondis and Zampro were effective in the 2012 experiment. Revus was ineffective in 2010 and 2011 when a single-nozzle boom was used. Limited efficacy detected in these experiments is at least partly due to the stringent assessment used: when assessing percent leaves affected, the severity of disease on the leaves is not taken into considered in the assessment. Best control (90-100%) was obtained with combination programs that were applied on a preventive, weekly schedule using a boom with drop nozzles in 2014 and also 2015 (2015a report). The programs included Ridomil, Quadris, Ranman, Revus, and K-Phite or Quadris, Ranman, Revus, and Orondis. K-Phite was applied at lowest label rate with all applications of the other fungicides based on the current opinion that this is the best use pattern for phosphorous acid fungicides. Many of these fungicides in different combinations in another experiment provided poor control at least partly due to an unintended lapse in the spray schedule with 13 days between applications and rainfall 9 days after the previous application (2015b report). Excellent control was obtained with 4 fungicide programs with Orondis, Revus, and Prophyt indicating this combination of chemistry was more important than specific timing for each fungicide (2016 report). Ranman applied in alternation with Revus + K-Phite was not quite as effective (89% vs 99% control). In 2021, fluoxapiprolin (new fungicide not registered yet) was most effective (64% control), Revus was least effective (43%), and 56% control was achieved with the grower recommended program (Ranman + K-Phite alt. Presidio + K-Phite alt. Orondis Ultra). Efficacy overall being lower than in previous years may be due to the impact of two storms (hurricane remnants) on application timing, product residues, and/or disease development. In 2022, an objective was to determine if downy mildew can be effectively managed with a weekly fungicide program applied on an IPM schedule (applications started after symptoms were found) to a resistant variety. Rutgers Passion DMR provided a higher degree of suppression than in 2021: 96% control obtained with untreated plants compared with untreated plants of a susceptible variety. Thus it is not surprising there was numerically but not significantly less downy mildew with the fungicide programs (alternation of Ranman + K-Phite, Presidio + K-Phite, and Orondis Ultra). This program applied on a preventive schedule to a susceptible variety provided only 66% control, which was significantly less than control achieved with the resistant variety.
These results support the recommended management program of a downy mildew resistant variety treated with a weekly fungicide program that is started before disease onset (preventive) or on an IPM schedule implemented with weekly scouting for symptoms.
Click on year below to get report with details about each experiment. ‘Photos’ with year indicates webpage with photographs from the experiment.
2022 | 2022 Photos | 2021 | 2021 Photos | 2016 | 2015a | 2015b | 2014 | 2013 | 2012 | 2011 | 2010
View article in the journal Plant Disease on this work.
Fungicide Evaluations – Organic Products
Products evaluated singly were Actinovate, BioGuard*, Companion*, Organocide*, Oxidate, Procidic, Regalia, Sporatec*, Sonata*, and Timorex Gold* (*product not registered or not labeled for this use). All provided little to no control based on percentage of leaves with symptoms, which is a rigorous assessment measure, but realistic reflecting the level of control needed to produce a marketable crop. All products tested singly were applied on a preventive, 7-day schedule with the exception of OxiDate, which was applied twice weekly in 2011. Applications were made with a single nozzle boom over the top of plants in 2010 and 2011, when the focus of evaluations was on products approved for organic production and other biopesticides. However, control of downy mildew was not achieved with the organic products tested singly in 2012 and the combination programs tested in 2013, 2014, and 2015, which were all applied with a boom with three nozzles per plant, two of which were drops. The combination program consisted of Regalia applied to soil starting at transplanting followed by Actinovate alternated with Trilogy applied to foliage in 2013 and 2014 or MilStop + Double Nickel alternated with Regalia + Double Nickel + Cueva and then Trilogy applied to foliage in 2015. The foliage sprays were made approximately twice weekly in 2014 and 2015 (2015a report), and started at least 24 days before symptoms were found in the experiment. These combination programs were also tested on a moderately resistant variety, Eleonora; but using this integrated program (fungicides applied to a resistant variety) also did not result in successful control. No treatments were effective in another experiment with organic products (Double Nickel, Double Nickel + Regalia, Procidic, and Sil-Matrix) and a non-organic biopesticide (Oso) all applied in alternation with a copper fungicide, Cueva (2015c report). Cueva was effective in the 2016 experiment based on defoliation ratings. Procidic was not effective in this field experiment but was in a greenhouse experiment with plants dipped in fungicide solution to examine efficacy without inadequate spray coverage being a confounding factor. Focus of research conducted in 2019 and 2020 was evaluating biopesticides on a new resistant variety providing a good degree of suppression. The resistant variety provided too high a level of suppression of downy mildew in 2019 to be able to detect a benefit of any treatments. All treatments tested in 2020 were effective. The organic treatments were LifeGard and Stargus applied with a copper fungicide, Cueva and Kocide 3000-O (4 treatments), and Regalia + Stargus alternated with EcoSwing + Badge X2.
Focus of research conducted in 2019, 2020, 2021, and 2022 was evaluating biopesticides on a new resistant variety that had exhibited good suppression, but not sufficient to avoid reduced marketability, in the resistant variety evaluation in 2018. The resistant variety provided too high a level of suppression of downy mildew in 2019 and 2022 to be able to detect a benefit of any treatments. All treatments tested in 2020 were effective. The organic treatments were LifeGard and Stargus applied with a copper fungicide, Cueva or Kocide 3000-O (4 treatments), and Regalia + Stargus alternated with EcoSwing + Badge X2. No treatments tested in 2021 were effective (including Regalia + Stargus alt. EcoSwing + Badge X2) likely at least partly because the resistant variety was not as effective as in 2018 and 2019 and because of the impact of two major storms (hurricane remnants) on application timing, product residues, and/or disease development. Treatments tested in 2022 were an experimental product and Regalia + Stargus alternated with EcoSwing + Badge X2.
Acknowledgment: this research was mostly funded by the IR-4 Project, Biopesticide and Organic Support Program
Click on year below to get report with details about each experiment. ‘Photos’ with year indicates webpage with photographs from the experiment.
2022 | 2022 Photos | 2021 |2021 Photos | 2020 | 2020 Photos | 2019 | 2016 | 2015a | 2015c | 2014 | 2013 | 2012 | 2011 | 2010
Plant Resistance Evaluations – Commercial Varieties, Experimental Varieties, and Breeding Lines
Excellent suppression of downy mildew was achieved in 2013 and 2014 with some resistant experimental varieties developed at Rutgers University. They performed at least as well as resistant breeding lines and inherently resistant spice basil types. No symptoms were observed on some in 2014. A commercial resistant variety, Eleonora, exhibited some suppression. Experimental varieties from Enza Zaden USA, Inc. and PanAmerican Seed performed better than Eleonora in 2015. M4828Z has been commercialized and named Everleaf Genovese and Pesto Party (marketing name for Burpee).
High to very high degree of suppression was demonstrated by newer resistant varieties evaluated since 2018, including varieties released from Rutgers. See table below. Degree of control of downy mildew provided by the four resistant varieties developed at Rutgers was not as good in 2020 and 2021 as in 2018, 2019, and 2022 perhaps because conditions were more favorable. There is concern the pathogen could evolve to be able to overcome host resistance. Eleonora was not as effective as the new varieties. No to very few symptoms or signs of downy mildew were found on plants of Amazel and Pesto Besto (Proven Winners) and several varieties of Prospera (Genesis Seeds), most notably in 2020 and/or 2021 when downy mildew became more severe on the Rutgers DMR varieties than in previous years. Variety ranking based on average rating from 12 growers in 2018 was Amazel (9.1 for appearance, 6.3 for taste, 8.6 for marketability), Passion (7.6, 6.8, 7.6), Prospera (7.5, 6.5, 6.6), Obsession (6.8, 6.2, 6.6), and Thunderstruck (5.9, 6.4, 5.2). All ratings and comments.
Click on year below to get report with details about each experiment. ‘Photos’ with year indicates webpage with photographs from the experiment.
2022 | 2022 Photos |2021 | 2021 Photos | 2020 | 2020 Photos | 2019 | 2019 Photos | 2018 | 2018 Photos | 2015d | 2014a | 2014b | 2013a | 2013b
| Variety | Control (%) based on AUDPC values compared to susceptible variety | ||||
| 2018 | 2019 | 2020 | 2021 | 2022 | |
| Eleonora | – | 34 | 26 | – | – |
| Rutgers Devotion DMR | 64 | 99 | 52 | 46 | 98 |
| Rutgers Obsession DMR | 48 | 99 | 56 | – | 95 |
| Rutgers Passion DMR | 80 | 93 | 79 | 59 | 97 |
| Rutgers Thunderstruck DMR | 81 | 99 | 53 | – | 99 |
| Amazel; Pesto Besto in 2021 | 100 | 98 | 100 | 100 | – |
| Prospera CG1 | 100 | 100 | 100 | 100 | 100 |
Results from Monitoring Program started in 2009
First observations of basil and cucumber downy mildews at LIHREC
Onset of downy mildew development at LIHREC is very regular, with first symptoms found between 4 and 19 August since 2009; in contrast, first symptoms of downy mildew were found in cucumber from 17 July to 7 September over the years.
| Basil | Cucumber | |
| 2009 | 5 Aug | 27 Jul |
| 2010 | 10 Aug | 7 Sep |
| 2011 | 19 Aug | 1 Aug |
| 2012 | 16 Aug | 17 Jul |
| 2013 | 6 Aug | 22 Jul |
| 2014 | 18 Aug | 2 Sep |
| 2015 | 10 Aug | 10 Aug |
| 2016 | 15 Aug | 8 Aug |
| 2017 | 4 Aug | 31 Jul |
| 2018 | 7 Aug | 14 Aug |
| 2019 | 16 Aug | 19 Aug |
| 2020 | 17 Aug | 17 Aug |
| 2021 | 3 Aug | 30 Jul |
| 2022 | 27 Jul | 2 Aug |
Extension presentations
- Downy Mildews of Basil, Spinach, & Other Crops handout and presentation at PASA Conference Feb 2018
- Field Studies on Managing Basil Downy Mildew in New York. Proceedings and presentation at 2019 New Jersey Agricultural Convention and Trade Show Feb 2019
Research presentations
- A Map-Based Monitoring System for Basil Downy Mildew. USDA NIFA Basil Workshop. Belle Glade, FL. Dec 2019.
- Update on Research Being Conducted in NY Evaluating Fungicides and Resistant Varieties. USDA NIFA Basil Workshop. Belle Glade, FL. Dec 2019.
Extension articles and meeting proceedings