Tomato and potato producers in eastern and central Kentucky should be advised of recent confirmations of late blight in western North Carolina and eastern Tennessee. Late blight is caused by Phytophthora infestans, an oomycete pathogen, and usually advances from the south on wind currents.
Late Blight Symptoms
Symptoms of late blight include lesions on young leaves that start as pale green, then quickly progress to irregular brown areas (Figure 1). Stems (Figure 2) and fruit can also be affected, with greasy, gray-brown lesions developing on fruit (Figure 3). Under conditions of high humidity, white sporulation is usually apparent on all types of infected tissue (Figures 2 and 3). Unlike early blight and Septoria leaf spot, which start in older plant tissue, late blight will often initiate in younger plant tissue.
Late Blight Disease Management
Under cool, wet conditions, late blight can progress very quickly, so growers hoping to extend their season well into October may want to consider applying fungicides. Greenhouse growers with significant production time left should consider Revus, Revus Top, or Catamaran. Curzate, Gavel, Tanos, or copper with excellent coverage should also provide some control in greenhouse tomato. Field producers with significant lengths of season left will want to consider Presidio, Zampro, Ridomil Gold products, Revus Top, or chlorothalonil with excellent coverage. Tanos, Gavel, Curzate, Ranman, Cabrio, or Previcur Flex should also provide some control in the field.
Kentucky Late Blight Situation
To date, there have been no identifications of late blight on tomato or potato in Kentucky. If late blight is suspected in either crop, local Extension professionals should be contacted immediately for confirmation. To help assess individual farm risks, USAblight has current maps of confirmed late blight throughout the U.S.
- Vegetable Production Guide for Commercial Growers (ID-36)
- IPM Scouting Guide for Common Pests of Solanaceous Crops in Kentucky (ID-172)
- Late Blight of Tomato (PPFS-VG-13)
By Emily Pfeufer, Assistant Extension Professor for Vegetables and Tobacco