Angular Leaf Spot of Cucurbits

Pseudomonas syringae pv. lachrymans

Description:

A bacteria that causes small, water soaked spots on leaves and grow to about 3 mm diameter then become brown and angular on the upper surface and shiny white underneath. Eventually the centres may dry and crack and fall away leaving a hole in the leaf. Lesions may also appear on petioles, stems and fruit. Immature fruit may drop off and mature fruit may develop a brown rot underneath the spot, which may dry to leave a white crusty residue.

Species Affected:

Cucumber, Marrow, Pumpkin, Rockmelon, Squash, Watermelon.
Lebanese Cucumbers are particularly susceptible.

Biology:

Spread by raindrop splash, running water and the hands and clothing of workers.
It enters the plant through wounds, stomata and hydathodes.
Spread most rapidly in warm humid conditions.

Life Cycle:

Origin and History:

Distribution:

Significance:

Management and Control:

Use seed from clean crops.
Rotate with resistant crops and avoid continuously cropping Cucurbits.
Remove and destroy infected plants immediately.
Destroy crop residues.
Avoid having foliage wet for long periods.
Don't work in wet crops

Related and Similar Species:

References:

1291

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.