Angular leaf spot

How to tell angular leaf spot from other cucurbit diseases

• Leaves develop small, angular, brown or straw-colored spots with a yellow halo.
• Leaf spots dry and drop out, leaving irregularly shaped holes in the leaves.
• Spots are typically confined within leaf veins. 
• Water-soaked tan, small circular spots on fruit.
• Bacterial soft rot often develops after fruit spots and rots the entire fruit.
• Sticky drops of whitish liquid form on the underside of the leaf when wet, dry to a crust when dry.

Biology

• Angular leaf spot is a bacterial disease caused by Pseudomonas syringae pv. lachrymans. 
• Although angular leaf spot can infect any of the cucurbit crops, it is less common on cucumber due to the availability of resistant varieties.
• Angular leaf spot thrives in warm humid conditions.
• The bacteria can infect all cucurbit crops and will infect all above ground parts of the plant including leaves, fruit and vines.
• When bacteria infects the fruit, it moves deep into the fruit and infects the seed.
• Contaminated seed can introduce the disease into a field.
• When humidity is high, a drop of clear to white sticky bacterial ooze forms on infections. These bacteria move from plant to plant on the hands and tools of workers, by insects or by splashing water.
• The pathogen can survive in plant debris for over two years.

Managing angular leaf spot in the home garden

Resistant varieties

• Many resistant varieties are available for cucumbers.

Cultural controls

• Buy clean seed from a reputable source. If saving seed, do not collect seed from infected plants.
• Rotate vegetables so two or more years go by before planting any member of the squash family in the same location.
• Use drip irrigation instead of overhead sprinklers if possible. If watering by hand, water at the base of the plant where the vine meets the soil. 
• Do not work in plants when leaves are wet.
• Remove and destroy infected fruit and vines at the end of the season in small gardens.