Cladosporium leaf spot of spinach

Symptoms

Small (1-5mm) round white spots on leaves with green halos, spots expand + darken to grey-brown with concentric rings, severe infection causes premature leaf senescence + downgrade of baby-leaf production, contaminated seed perpetuates the disease in clean rotations.

Plants affected

• spinach

Easily confused with

• bacterial 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 Cladosporium leaf spot of spinach on spinach?

Small (1-5mm) round white spots on leaves with green halos, spots expand + darken to grey-brown with concentric rings, severe infection causes premature leaf senescence + downgrade of baby-leaf production, contaminated seed perpetuates the disease in clean rotations.

Do I have to report Cladosporium leaf spot of spinach?

No. Cladosporium 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 Cladosporium 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.