Philippine downy mildew - Peronosclerospora philippinensis
Effective: January 1, 2020
Taxonomic Position: Sclerosporales : Sclerosporaceae
Pest Type: Fungi
Pest Code (NAPIS): FFABPMF
This pest is a member of the following surveys: Corn, Small Grains
These Approved Methods are appropriate for: 2025, 2024, 2023, 2022, 2021
Pest Information
CAPS Pest Datasheet: https://download.ceris.purdue.edu/file/4120
Pest Tracker: https://pesttracker.org/pest/FFABPMF
Hosts Identified in the CAPS Host Matrix:
Corn; Sugarcane
Pest is vectored by:
No known vector.
Survey
Approved Method(s)
| Method | Detail | NAPIS Survey Method |
|---|---|---|
| Visual | Collect symptomatic plants. Unsprayed, susceptible plants (sentinel plots) that are scouted regularly can be used for early detection. | 3031 - General Visual Observation |
Survey Recommendations
The following are recommendations for executing the survey using the approved methods for pest surveillance. The recommendations are developed through literature review and consultation with subject matter experts.
Signs:
Downy (grayish) fungal structures are observed primarily on the underside of the leaves.
Symptoms:
Chlorotic stripes/streaks are usually the first symptom observed. As the plant ages, leaves may narrow, become abnormally erect, and appear somewhat dried-out. As the corn plant matures, tassels become malformed and produce less pollen, ear formation is interrupted, and sterility of seeds can result.
There is a synergistic relationship between downy mildew fungi and maize streak virus (MSV) on corn. Infection by MSV can mask symptoms of downy mildew infection.
There is a synergistic relationship between downy mildew fungi and maize streak virus (MSV) on corn. Infection by MSV can mask symptoms of downy mildew infection.
Key Diagnostic or Identification
Approved Method(s)
ID/Diagnostic:
Preliminary Screening:
Morphological: Species are differentiated only by variations in the size and shape of their conidia (spores) and conidiophores (spore-bearing structure), and sometimes the presence or absence of oospores and differences in host ranges. See Table 2 in Smith and Renfro (1999) for characteristics of downy mildew on corn.
The CAPS-approved diagnostic method requires molecular analysis for species confirmation.
Screening:
Molecular: A Loop-mediated isothermal AMPlification (LAMP) assay is approved for rapid screening of Peronosclerospora philippinensis and P. sorghi. This method distinguishes endemic species, like P. sorghi, from the exotic P. philippinensis. A multiplex conventional PCR protocol is also available for screening.
To request a copy of these protocols, email the S&T Beltsville laboratory at APHIS-PPQCPHSTBeltsvilleSampleDiagnostics@aphis.usda.gov and use the subject line "Diagnostic protocol request".
Confirmation: Suspect positives should be sent to the S&T Beltsville laboratory for confirmatory analysis following the guidelines from the Federal Select Agent Program.
Morphological: Species are differentiated only by variations in the size and shape of their conidia (spores) and conidiophores (spore-bearing structure), and sometimes the presence or absence of oospores and differences in host ranges. See Table 2 in Smith and Renfro (1999) for characteristics of downy mildew on corn.
The CAPS-approved diagnostic method requires molecular analysis for species confirmation.
Screening:
Molecular: A Loop-mediated isothermal AMPlification (LAMP) assay is approved for rapid screening of Peronosclerospora philippinensis and P. sorghi. This method distinguishes endemic species, like P. sorghi, from the exotic P. philippinensis. A multiplex conventional PCR protocol is also available for screening.
To request a copy of these protocols, email the S&T Beltsville laboratory at APHIS-PPQCPHSTBeltsvilleSampleDiagnostics@aphis.usda.gov and use the subject line "Diagnostic protocol request".
Confirmation: Suspect positives should be sent to the S&T Beltsville laboratory for confirmatory analysis following the guidelines from the Federal Select Agent Program.
Mistaken Identities:
Peronosclerospora spp. and other downy mildew genera (including Sclerospora and Scleropthora).P. philippinensis is indistinguishable from P. sacchari by isozyme analysis and many experts have synomized the two species.
Notes:
Peronosclerospora philippinensis is on the Select Agent List.
References
If you are unable to find a reference, contact STCAPS@usda.gov. See the CAPS Pest Datasheet for all references.