KIERSTEN WISE
LEXINGTON, KENTUCKY
Frequent rainfall across Kentucky has increased concern about foliar diseases in corn, but the good news is that important diseases like Southern rust have not yet been confirmed in the state. Southern rust typically arrives in Kentucky in mid-July, and whether a fungicide will be needed to manage southern rust will depend on the crop growth stage at the time it is detected in an area. Fungicide applications may be needed to manage southern rust through the milk (R3) growth stage, although if corn received a fungicide application at VT/R1, it is less likely to need additional applications if southern rust arrives after VT/R1. Southern rust can be tracked on a map on the Crop Protection Network. On the map, red counties/parishes indicate that southern rust has been confirmed by university/Extension personnel. To date, southern rust has been slow to develop in states to our south, which has delayed its arrival in Kentucky. Most corn in the western part of Kentucky will likely be into R3 or beyond by the time southern rust arrives this year.
Tar spot was confirmed in Daviess County on July 14. Tar spot management is like southern rust management in that fungicide applications may be needed through R3 if the disease is confirmed in a field, and if a field has not already been sprayed at VT/R1. Most corn in Kentucky will be past the point of requiring management, but scouting should continue and fungicide application decisions made on a case-by-case basis.
Curvularia leaf spot is also very common in Kentucky this year. This is a relatively new disease in Kentucky, caused by the fungus Curvularia lunata. Small, tan to pale yellow lesions can be observed on the leaf, and the lesions are often surrounded by a brown or tan halo (Fig. 1). Curvularia leaf spot has reduced yield in some states, including Kentucky, but widespread yield loss has not yet been observed. More information on Curvularia leaf spot can be found in the UK Extension publication PPA-51: Curvularia leaf spot. ∆
KIERSTEN WISE
UNIVERSITY OF KENTUCKY
Figure 1. Symptoms of Curvularia leaf spot on corn (photo by Kiersten Wise).
LINK : Figure 1. Symptoms of Curvularia leaf spot on corn (photo by Kiersten Wise).
