Plant Pathology Infobytes

December 16, 1998
Turnips and Mustard Greens "Blighting Out"

Reports of blighted turnip and mustard greens in Mississippi gardens have been common over the past week. The problem is related to several fungus diseases which generally occur each season, but have been unusually severe this fall as a result of unseasonably warm weather and periods of heavy dewfall.

These diseases are white spot and downy mildew, and both are capable of blighting an entire planting of leafy greens. Symptoms of white spot include circular, gray to brown or almost paper white spots, with slightly darkened margins.

At first these spots are small, about one-eighth inch in diameter, but rapidly increase in size and number, and over a period of a week or so the entire leaf may become blighted. Downy mildew doesn't cause white spotting, but may be recognized by small yellow areas on the top sides of leaves. Often a whitish webbing of fungus growth is detectable on the bottom side of leaves, particularly in the morning following a heavy dew.

White spot and downy mildew are most severe when moisture is present on leaf surfaces. Moisture and temperatures in the 55 to 60 F range are favorable for germination of fungus spores which germinate and infect leaves. These conditions have lead to the severe blighting of leafy greens which has been widespread over the state in recent weeks.

The key to keeping greens blight-free is to start a control program before white spot or downy mildew become widely distributed. While there is little that may be done to save a severely blighted crop at this point in the season, drop by your County Extension Office for information which may be followed by home gardeners to control blight next season.

Note: Avoid saving mustard or turnip seeds from a planting where diseases were widespread ñ it's best to start the next crop fresh with a disease-free supply of seed.


Written by the late Dr. Frank Killebrew

A black line that separates the body text from footer information