The lesions are circular depressions with a diameter of 3-10 mm (0.12 - 0.4 inch). Hard spot (1) is the most typical and diagnostic symptom of black spot as the fruit mature, often appearing around color change.
Similar lesions can be seen on twigs and pedicles.įruit - lesions on fruit are so diverse that lesions are grouped into several types: 1.) hard spot 2.) false melanose/speckled blotch 3.) freckle spot (early virulent spot) 4.) virulent spot 5.) lacy spot 6.) cracked spot. They are rarely seen in well managed groves. Foliar lesions are most commonly seen on lemons. A yellow halo can be associated with the lesions. Young lesions are small, reddish, and slightly raised. The lesions are bordered with a dark brown ring. Leaf - older lesions are small, round, sunken necrotic spots with gray centers. Symptom development is increased in high light intensity, intensifying temperatures, drought, and low tree vigor. At this point the fungus may grow further into the rind producing black spot symptoms months after infection, often near or after harvest. Infections are latent until the fruit becomes fully grown or mature. Often late hanging fruit with lesions remain on the tree and spores can be washed onto young susceptible fruit. These spores are not considered a significant source of inoculum in climates with dry summers however, in climates with frequent summer rains, conidia play a larger role in the epidemic when there are multiple fruit ages present on trees simultaneously. Conidia are not wind-borne, but may reach susceptible fruit by rain splash. Spores are released when the leaf litter is wetted by heavy dew, rainfall, or irrigation and can be carried by air currents over long distances.ĭark brown or black pycnidia, structures that produce conidia, are formed on fruit, fruit pedicles and leaf lesions. Ascospores have never been found in fruit lesions or lesions on attached leaves. They are the most important source of inoculum, in some regions causing nearly all infections. citricarpa are able to infect susceptible tissues.Īscospores are found in microscopic fungal structures embedded in the leaf litter.
Fruit are susceptible from fruit set until 5-6 months later, when they become age resistant.īoth the ascospores (sexual spores) and the conidia ( asexual spores) of G. Inoculum in the leaf litter needs to be available during the period when the host is susceptible and the environment is favorable for infection. As in many diseases, timing is important for black spot to occur.