Crop scientists are asking farmers for help. They know plants were attacked by a bacterial disease called Goss's leaf blight and wilt. But University of Minnesota's (MSU) Dean Malvick wants farmers to send diseased leaves.


Goss's can reduce ear size, or at its worst, kill the plant completely. The disease has a long history in the U.S., but it remained fairly isolated for decades until recently. Malvick wants to know whether the bacteria affecting Minnesota fields are the same as the ones wilting corn across the Midwest, or whether they are some sort of variant.


The disease was first confirmed in Minnesota in 2009 in 2 fields. Last year [2010], there were maybe 40 fields infected. Reports of the disease have increased "dramatically" this year [2011] in the state.


Malvick said he doesn't have a final tally for 2011, but the area affected will be much higher than in 2010.


He said researchers don't know why Goss's is increasing so fast. Its rapid increase over the last few years is something researchers are concerned about.


Goss's wilt and blight of maize is caused by the bacterium Clavibacter michiganensis_ subsp.  nebraskensis. It is a persistent and economically serious disease of susceptible maize hybrids in several states of the USA. In 2009, it was reported for the 1st time outside the U.S., from Canada.


The bacterium can also affect some grasses, which may serve as pathogen reservoirs. Symptoms include systemic wilting of plants and/or leaf lesions and blighting. Infection of leaves, stems and roots occurs primarily through wounds (mechanical, hail, or insect damage), and plants are susceptible at all growth stages.


The pathogen is seed transmitted and overwinters on crop debris and maize kernels. Disease management includes cultural practices to minimise inoculum, crop rotation, and use of resistant crop varieties.


Other subspecies of C. michiganensis affecting different hosts are found elsewhere, including sepedonicus (potato ring rot) and michiganensis (bacterial canker of tomatoes), which can cause severe yield losses on their respective hosts.