Cause Hyaloperonospora camelinae (syn. = Peronospora camelinae, P. parasitica), an oomycete that is favored by cool, wet conditions. In North America, it was first reported in Canada during 1955, where partial host resistance was also identified. This pathogen has been found on camelina grown in western Montana and Nebraska. The pathogen can survive for an unknown length of time in infected plant residues but it is unclear whether it is transmitted by seed. Sporulation within the field can lead to significant incidence of disease in a field.
Symptoms Whitish to light-gray growth can be found growing on stems, pedicels, pods, and on the underside of leaves and can superficially resemble powdery mildew especially on stems. The whitish growth will turn grayer once spores are being produced. Infections may be localized or systemic. Localized leaf infections can be accompanied by pale green to light yellow spots on the upper leaf surface. Systemic infections of plants or plant parts may cause portions of the plant to appear deformed. Severely affected plants will produce little seed.
Cultural control
- Rotate camelina with grassy hosts; ideally planting no more than once every four years.
- Reduce or eliminate overhead watering.
- Promote decomposition of infected plant residues.
- Avoid planting seed harvested from downy mildew-infected plantings.
Chemical control
- Quadris Flowable (Group 11) and other azoxystrobins are registered at 6 to 15.5 fl oz/A. Do not make more than one (1) application of any Group 11 fungicide before alternating to a labeled fungicide with a different mode of action. Preharvest interval is 30 days. 4-hr reentry
Biological control Efficacy unknown in Oregon.
- Stargus at 2 to 4 quarts/A plus a nonionic surfactant. Preharvest interval is 0 days. 4-hr reentry. O
References Babiker, E.M., Hulbert, S.H., and Paulitz, T.C. 2012. Hyaloperonospora camelinae on Camelina sativa in Washington State: Detection, Seed Transmission, and Chemical Control. Plant Dis. 96:1670-1674.
Putnam, M.L., Serdani, M., Ehrensing, D., and Curtis, M. 2009. Camelina infected by downy mildew (Hyaloperonospora camelinae) in the Western United States: A first report. Online Plant Health Progress doi:10.1094/PHP-2009-0910-01-BR.