First Report of Tar Spot of Maize (Zea mays) Caused by Phyllachora maydis in Pennsylvania

Tar spot on corn (Zea mays L.), caused by the obligate fungal pathogen Phyllachora maydis Maubl., was first detected in the United States in 2015. Currently, the disease has been detected in 172 counties across Florida, Illinois, Indiana, Iowa, Michigan, Ohio, and Wisconsin. Although observations indicate that P. maydis likely overwinters in the region, this has not been conclusively proven. Samples of corn foliage heavily infected with P. maydis were recovered from two fields in northern Illinois in March 2019. Ascospores were extracted and were applied to corn seedlings under controlled greenhouse conditions. Symptoms of tar spot were observed 17 days after inoculation, and ascospores were extracted from stromata to confirm P. maydis. This is the first conclusive proof that P. maydis can overwinter the United States. We also present a preliminary greenhouse method that, if optimized, may be used to study this pathosystem under controlled conditions.

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Native parasitoids of Dalbulus elimatus and Dalbulus maidis (Hemiptera: Cicadellidae) in winter crops of central Mexico

The Canadian Entomologist ◽

10.4039/n06-053 ◽

2007 ◽

Vol 139 (5) ◽

pp. 722-727 ◽

Cited By ~ 3

Author(s):

Gustavo Moya-Raygoza

Keyword(s):

Zea Mays ◽

Hordeum Vulgare ◽

Annual Cycle ◽

Winter Season ◽

Central Mexico ◽

Dalbulus Maidis ◽

First Report ◽

Native Parasitoids ◽

Winter Crops ◽

Corn Leafhopper

AbstractNative parasitoids of the adult Mexican corn leafhopper, Dalbulus elimatus (Ball), and corn leafhopper, Dalbulus maidis (Delong and Wolcott), are described and their rates of parasitism on maize, Zea mays L., common barley, Hordeum vulgare L., and sorghum, Sorghumbicolor (L.) Moench (Poaceae) in central Mexico are determined. The survey was conducted throughout an annual cycle, with sampling of the previous season's crops when they were available. Leafhoppers showing evidence of parasitism were reared individually in the laboratory to obtain adult parasitoids. Adult D. elimatus were parasitized on winter maize, barley, and sorghum by the fly Eudorylas subopacus (Loew) (Diptera: Pipunculidae) and the wasp Gonatopus bartletti Olmi (Hymenoptera: Dryinidae), whereas adult D. maidis were parasitized by these fly and wasp parasitoids on winter maize only. The highest rates of parasitism of D. elimatus by E. subopacus were 57.4% on maize, 39.6% on barley, and 48.8% on sorghum. The highest rate of parasitism of D. maidis by E. subopacus was 20.4% on maize. In contrast, the highest rates of parasitism of D. elimatus by G. bartletti were 9.4% on maize, 2.7% on barley, and 25.8% on sorghum. The highest rate of parasitism of D. maidis by G. bartletti was 7.1% on maize. These results indicate that winter crops are habitats of E. subopacus and G. bartletti during the winter season. This is the first report of D. elimatus and D. maidis being parasitized by E. subopacus and of D. elimatus being parasitized by G. bartletti.

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