Java downy mildew - Peronosclerospora maydis
Effective: May 15, 2020 - December 31, 2020
Taxonomic Position: Sclerosporales : Sclerosporaceae
Pest Type: Fungi
Pest Code (NAPIS): FFABPMD
This pest is a member of the following surveys: Corn
These Approved Methods are appropriate for: 2020
Pest Information
CAPS Pest Datasheet: https://download.ceris.purdue.edu/file/3116
Pest Tracker: https://pesttracker.org/pest/FFABPMD
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 on the chlorotic streaks.
Symptoms:
White to yellow stripes/streaks, which become necrotic and brown, are usually the first symptom observed.
When systemic, the pathogen causes severe chlorosis in the upper leaves.
Infected plants may be stunted and sterile and often lodge (fall over).
Plants may develop multiple and deformed cobs, leaflike tassels and cobs, combined tassels and cobs, and either elongated or shortened stalks.
When systemic, the pathogen causes severe chlorosis in the upper leaves.
Infected plants may be stunted and sterile and often lodge (fall over).
Plants may develop multiple and deformed cobs, leaflike tassels and cobs, combined tassels and cobs, and either elongated or shortened stalks.
Key Diagnostic or Identification
Approved Method(s)
ID/Diagnostic:
- 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. If you have questions about morphological identification, you may contact the PPQ National Mycology Specialists (PPQNISNTMycology@usda.gov) for guidance.
- Molecular: The barcoding protocols and universal primers described in Choi et al. (2015) may be used for species confirmation. You may contact the S&T Beltsville laboratory at APHIS-PPQCPHSTBeltsvilleSampleDiagnostics@aphis.usda.gov if you need additional guidance for molecular identification.
Mistaken Identities:
Peronosclerospora spp. and other downy mildew genera (including Sclerospora and Scleropthora).
References
- Choi et al.. 2015. Towards a universal barcode of oomycetes - a comparison of the cox1 and cox2 loci. Molecular Ecology Resources 15(6): 1275-1288.
- Smith, D.R., and Renfro, B.L. 1999. Pg. 26, 28. In: D. G. White (ed.) Compendium of Corn Diseases, 3rd ed. APS Press, St. Paul, MN. 78 pp.
If you are unable to find a reference, contact STCAPS@usda.gov. See the CAPS Pest Datasheet for all references.