Posted by: marinvit | May, 2010

Orchid Diseases- Fingus

Fungus


– two types cercospora sp and anthracnose species

– causes spotting of the leaves and pseudobulbs, occasionally flowers

– rarely causes death, scars remain for life of leaf

– more prevalent in cold, moist, & still conditions

– especially active on devitalised and dead plants

Cercospora symptoms

Chlorosis – fine yellow spots starts on undersurface, first enlarging irregularly-followed by necrosis, death and blackening of tissue followed by irregular enlargement, dead tissue falls out, leaves die

Anthracnose symptoms

Brown irregular discoloration usually sunken, sharply defined between infected & healthy tissue, spore pustules – little brown or black spheres develop (don’t confuse with thrips droppings)

Botrytis symptoms

– flowers only infected, small brown spots, enlarge very little, pink margin

Control:

Prevention

– cleanliness and strict hygiene

– adequate air movement

– control of humidity levels and temperature

– removal of leaves & especially flowers (botrytis is saprophytic)

Cure

– spray at regular intervals usually weekly

– use a wetting agent

– follow safety procedures as for pests

Chemicals

– usually wettable powders

– benlate can cause viral like symptoms in excess

– caftan, zineb, ferbam, daconjl, tersan, thiram, mancozeb

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