Damping-off

Other Common Names

seedling blight

Scientific Name of Pathogen

The pathogens associated with damping-off or seedling blight include species of Calonectria, Fusarium, Gliocladium, Phytophthora, Pythium, Rhizoctonia, Sclerotium and Thielaviopsis. The list of pathogens may be greater than this.

Except for Phytophthora, the pathogens belong to the Kingdom Fungi. Phytophthora belongs to the Kingdom Stramenopila.

Hosts

All palms are considered potential hosts of these pathogens.

Distribution

The pathogens are worldwide in distribution.

Symptoms/Signs

Damping-off (seedling blight) disease occurs after germination but before the seedling has more than a few leaves. If the disease occurs soon after germination, the radical (first root emerging from seed) or hypocotyl may rot, and no seedling leaves develop. This is referred to as pre-emergence damping-off.  Alternatively, one or two seedling leaves may develop, but then suddenly wilt and die, usually due to a rot at the leaf base/soil interface (Fig. 1). The latter would be referred to as post-emergence damping-off.

May Be Confused With

Seed germination of some palm species can be difficult, even under optimal germination conditions. Percent germination among palm species can vary from nearly 100% germination to less than 25% germination. For the latter, the poor germination is not necessarily due to pathogens. Furthermore, many palm species require more than 100 days (sometimes a year) to germinate. Therefore, do not jump to the conclusion that damping-off disease is the cause of a low germination rate unless you are familiar with the germination pattern of that particular palm species or you confirm either pre-emergence or post-emergence damping-off.

December 1, 2010