Figure 1. Bacterial leaf streak symptoms on corn leaf. Notice the narrow streaks with wavy margins. Courtesy: Tamra Jackson Ziems
Two corn samples submitted to the South Dakota State University Plant Diagnostic Clinic from Turner County were confirmed to have bacterial leaf streak. This is the first report of this disease in South Dakota in 2017. Bacterial leaf streak is a new disease of corn and its symptoms can resemble gray leaf spot, a fungal disease. It is important to submit suspected corn samples to the clinic to confirm that it is bacterial leaf streak, especially if a fungicide decision is to be made to manage fungal diseases with similar symptoms.
Bacterial leaf streak (BLS) develops as brown, yellow, orange or tan narrow irregular wavy streaks on corn leaves (Figure 1). The wavy margins and the brownish-orange color of bacterial leaf streak distinguish it from gray leaf spot (Figure 2). In Nebraska, where this disease was first reported in 2016, it was found on corn as early as V7. Sometimes bacterial leaf streak symptoms may be confused with sunscald (Figure 3).
Figure 2. Gray leaf spot on corn. Notice the shorter, tan spots.
Figure 3. Sunscald symptoms on corn.
Inoculum Source & Yield Impact
The bacterium that causes bacterial leaf streak survives on corn residue and is splashed onto plants by rain. The bacteria is thought to infect plants through natural openings. It is not known at this time if the bacteria can be transmitted through seed or if there are alternative hosts. The impact of this disease on corn yield is also not yet known, but yield loss is expected to be minimal if mild symptoms are observed after corn has reached dent growth stage.
Because this is a new disease on corn, no information is available on corn hybrid variation in susceptibility to bacterial leaf streak. Currently, cultural practices used to manage other bacterial diseases such as Goss’s wilt should be used to manage bacterial leaf streak. These include crop rotation and tillage to bury residue where practical (not recommended where soil erosion is likely to occur). No chemicals are effective against bacterial leaf streak.