Fire spot
Heterosporium gracile
What is Fire Spot (Heterosporium gracile)?
Fire spot, caused by the fungal pathogen Heterosporium gracile, is a plant disease affecting various rhizomatous and bulbous Iris species, as well as plants like Gladiolus, Freesia, and Narcissus from the Iridaceae family. Infected plants display numerous round or elongated leaf spots, initially cinnamon brown and later turning buff-colored or pale greyish white. These spots often have a narrow dark brown margin and can be surrounded by a chlorotic halo.
What does Fire spot (Heterosporium gracile) occur?
Heterosporium gracile reproduces asexually through the production and dispersal of conidia. Conidia are formed on conidiophores that emerge from stromata. These solitary or paired conidia, measuring up to 80 µm in length, are released and can be spread by wind, water, or physical contact. Upon finding suitable conditions, the conidia germinate and initiate new infections on susceptible host plants. It is worth mentioning that while asexual reproduction is the primary mode, some Heterosporium species may have additional sexual reproductive stages.
Symptoms
2 - Impact on Economic and Environmental
Heterosporium gracile outbreaks can lead to the loss of susceptible plant species, impacting biodiversity. The presence of this pathogenic fungus can affect soil microbial communities and nutrient cycling. Commercial cultivation, reduces aesthetic value and marketability, resulting in economic losses.
Solutions
1 -
• Select and plant resistant cultivars or species that are less susceptible to H. gracile. • Avoid overhead irrigation that can create favorable conditions for disease development. • Remove and destroy infected plant debris to prevent disease spread. • Rotating your crops will help to reduce the build-up of the fungus in the soil.
2 - Chemical Control
• Some of the most common fungicides used to treat this disease include Mancozeb, Thiram, Carbendazim, Propiconazole and Difenoconazole. • It is important to choose a fungicide that is labeled for use on your plant species and that is effective against fire spot heterosporium gracile. Be sure to follow the directions on the label carefully when applying the fungicide.
