The Purdue University Plant and Pest Diagnostic Laboratory (PPDL) have warned tomato growers to watch out for late blight, a destructive disease as they discovered this fungus like organism on several tomato samples from Tippecanoe County in west-central Indiana.

Late blight, a plant disease caused by the fungal-like organism Phytophthora infestans was confirmed on a tomato sample submitted to the PPDL on August 19th, 2013.

Symptoms include olive-green or brown spots on leaves and white fungal growth during humid conditions such as in the early morning or after rain. Brown to blackish lesions also grows on upper stems, and brown spots develop on tomato fruit.

The disease multiplies quickly in tomato and potato plantings in cool and wet conditions, while it decreases in hot and sunny weather conditions.

"All growers should assume their crops may eventually be affected and thus should be on a weekly schedule to both thoroughly inspect their potato and tomato plantings and apply fungicides if the weather remains cool and cloudy," said Tom Creswell, PPDL director.

Experts said that diseased plants in home gardens should be removed immediately and be either burned or disposed.

"Do not compost affected plants, as spores will spread from this infected debris to other healthy tomato plants," they said.

Since there are several similar diseases affecting tomato leaves, identification of late blight requires close examination by a microscope.

Topics Indiana, Purdue university