bacterial leaf spot of spinach

Symptoms

Small angular water-soaked spots on leaves with yellow halos (vein-bounded), spots turn dark brown + papery dry, severe infection causes leaf collapse + market loss, baby leaf production particularly vulnerable, wet weather + overhead irrigation accelerate spread.

Plants affected

• spinach

Easily confused with

• spinach downy mildew

  How to tell them apart: Peronospora effusa (spinach downy mildew) starts as pale, irregular chlorotic blotches on the upper leaf surface; the giveaway is a felty grey-violet sporulation that forms on the LOWER surface directly beneath those yellow patches in cool, humid, dewy conditions. Pseudomonas syringae pv. spinaciae (bacterial leaf spot) instead makes small, discrete, angular water-soaked spots that dry to tan-brown papery necrosis with a faint yellow halo, scattered between veins and often appearing greasy/translucent when held up to the light, with NO fuzzy growth underneath. If you flip the leaf and see downy mould, it is the oomycete; if the spots stay dry, sharp-edged and fungus-free, it is the bacterium.

• Cladosporium leaf spot of spinach

  How to tell them apart: On spinach, Cladosporium variabile makes small (1-3 mm), neatly circular tan spots on the upper leaf surface, each ringed by a distinct darker margin; the giveaway is the velvety olive-black to dark green-brown fuzz (fungal sporulation) that develops in the spot centres as they age. Pseudomonas syringae pv. spinaciae instead starts as greasy, water-soaked spots that enlarge into angular, vein-delimited dark-brown lesions (often with a faint yellow halo) and never grow any fuzz or mould; held up to the light the young spots look translucent and oily. In short: round + dry centre with olive velvet = the fungus; angular, vein-bounded, water-soaked and bare = the bacterium. Cladosporium favours cool, very humid spells, while the bacterial spotting spreads fastest after rain or overhead irrigation that splashes the leaves.

Common questions

How do I recognise bacterial leaf spot of spinach on spinach?

Small angular water-soaked spots on leaves with yellow halos (vein-bounded), spots turn dark brown + papery dry, severe infection causes leaf collapse + market loss, baby leaf production particularly vulnerable, wet weather + overhead irrigation accelerate spread.

Do I have to report bacterial leaf spot of spinach?

No. bacterial leaf spot of spinach is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is bacterial leaf spot of spinach treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.