Corn grey leaf spot
There are two populations of Cercospora zeae-maydis, distinguished by molecular analysis, growth rate, geographic distribution, and cercosporin toxin production.
nov. in that it has a faster growth rate in artificial media, the ability to produce the toxin cercosporin, longer conidiophores, and broadly fusiform conidia.
[15][3][4] Primary inoculation occurs on lower regions of younger leaves, where conidia germinate across leaf surfaces and penetrate through stomata via a flattened hyphal organ, an appressorium.
The fungus overwinters as stromata (mixture of plant tissues and fungal mycelium) in leaf debris, which give rise to conidia causing primary inoculations the following spring and summer.
[15] Corn grey leaf spot is found by Crous et al. 2006 to flourish under extended periods of high relative humidity[3][4] (over two days) and free moisture on leaves due to fog, dew, or light rain.
[1] In order to best prevent and manage corn grey leaf spot, the overall approach is to reduce the rate of disease growth and expansion.
High risks for corn grey leaf spot are divided into eight factors, which require specific management strategies.
The most proficient and economical method to reduce yield losses from corn grey leaf spot is by introducing resistant plant varieties.
[19] If grey leaf spot infection is high, this variety may require fungicide application to achieve full potential.
[22] The amount of initial inoculum will be reduced when a crop other than corn is planted for ≥2 years in that given area; meanwhile proper tillage methods are carried out.
Currently there are 5 known fungicides that treat Corn grey leaf spot:[24] The impact of GLS is more severe if plants are affected early in their development.
Early planting can help reduce yield losses by ensuring the crop is at a later stage of grain fill when conditions are typically favorable for GLS development.
[24] By removing weeds, above ground airflow to the crop is increased, relative humidity is decreased, and it limits infection at the most susceptible times.
[26] Before 1970, corn grey leaf spot was not prevalent in the United States, however the disease spread during the mid part of the decade throughout low mountain regions of North Carolina, Kentucky, Tennessee, and Virginia.
Today, the disease has expanded to Delaware, Illinois, Indiana, Iowa, Maryland, Missouri, Ohio, Pennsylvania and west Tennessee.
Corn grey leaf spot can be an extremely devastating disease as potential yield losses range from 5 to 40 US bushels per acre (440 to 3,480 L/ha).
This occurs when Cercospera zeae-maydis infects foliar tissue and reduces the plant's ability to photosynthesize and produce byproducts of the process (ex.
