Causal Agent:
Pseudomonas syringae pv. lachrymans

Distribution:
Worldwide

Symptoms:
The disease occurs on most cucurbits, but it is most common on cucumber. Leaf symptoms appear first as small, water-soaked areas on the under surface which become angular in shape. These angular spots are restricted by the small veins of the cucumber leaf. Later, these spots turn brown and may develop yellow haloes. Finally, the centers of the spots disintegrate giving a tattered appearance to the leaves. Often, under humid conditions, such as in the early morning, milky droplets can be seen coming from the watersoaked areas on the lower leaf surface. Infections on stems, petioles and fruits develop watersoaked spots which enlarge and become covered with a white crust. Infection of young fruit may result in curved or deformed fruit later. Secondary soft rots usually develop on infected fruit.

Conditions for Disease Development:
The organism can survive from one season to the next on infected plant debris or on the seed. Humid conditions, which lead to watersoaked tissue, favor development of the disease. Wind-blown rain or overhead irrigation leads to rapid spread of the disease. The disease can also be spread by workers picking fruit while the foliage is wet. Angular leaf spot is especially common on sandy soils where wind-blown sand creates sites for infection on leaves, stems and fruit.

Control:
A crop rotation program of at least two years is suggested as a preventative measure. Using seed free of the angular leaf spot organism is important for disease control early in the season. Initiating a 5-10 day copper spray at first appearance of leaf spotting may reduce the disease. Do not use irrigation water from sources that drain cucumber fields. Resistant varieties should be used.