Pull up and destroy the first few plants which appear to have symptoms. Before destroying weeds and pulling up plants, it is best to kill the aphids on them first. Otherwise these aphids will move from the dying plants into the field. Mosaic-resistant varieties are now available for most cucurbits. The older leaves of an affected vine are covered with tiny, white, necrotic flecks.
Damage can become so severe that leaves fall off the plant.
The cause is air pollution. Exhaust gases from internal combustion engines become trapped by a temperature inversion during hot, still humid days. Plants recover putting out normal leaves when air quality improves. For insect information, please see specific crop.