National Geographic : 1969 Jan
Spotting sick potatoes INFRAREDEKTACHROMES BYFRANKLINE. MANZERANDGEORGER. COOPER© N.G .S . Like flower beds aflame with bloom, potato fields blaze scarlet in an infrared photograph taken at the Maine Agricultural Experiment Station near Presque Isle (above). To help farmers detect plant diseases, pathologists intro duced late-blight fungus, then made successive infrared photographs. In about a week smudges clouded a picture evidence of diseased leaves that reflect less IR. Two more days elapsed before damage became evident on the ground (right). Blight checkerboards the center field three weeks later (below); fungicides saved the healthy plots. Other fields lie darkened by a spray that withers plants to hasten ripen 50 ing of the potato tubers.