Anthracnose is a disease noticed on cucurbits in warm and high moisture conditions. The symptoms are noticed on leaves as necrotic lesions with or without cracked centers.
In the early stages of infection spots on the leaves start as small spots that may resemble deny mildew, but as the lesions expand irregular shape of lesions become apparent.
The larger lesions can be seen in leaves inside the canopy or leaves exposed outside under high moisture conditions. The lesions tend to have a marginal yellow discoloration around it.
The lesion is unique in its appearance with intendations around it, and this is clearly evident on the underside of the leaves also especially in watermelon and cantaloupe.
In cantaloupe, lesions have similar appearance to like that in watermelon, but intonations around the lesion tends to be less prominent, but present.
Irregular shaped lesions which are necrotic are the first signs of the disease in cantaloupe and the lesions tends to be lighter brownish than the darker shades normally seen in watermelon.
In cucumbers, the lesions unlike in cantaloupe and watermelon which are irregular tends to be small circular spots. The disease can cause leaf blighting and leaf drop in cucumber.
A set fo leaves with irregular lesions to the left and top which are typical symptom of anthracnose. The leaf to the right with circular patterns is characteristic symptom of gummy stem blight.
Regions with necrotic lesions lead to severe blighting and leaf drop under ideal conditions for disease occurrence as seen here in a watermelon field.
Watermelon fruits that are severely infected most commonly have the symptom of black sunken areas which can be few to many. Similar lesions can be found in other cucurbits.
Under high moisture conditions especially in fall production in Florida or wet spring season large masses of salmon colored spores can be noticed which is characteristic of the pathogen.
Pumpkin can be severely affected in the field with few to many lesions that can vary in size. Both leaf and fruit symptoms can be noticed at the same time, but leaf symptoms typically start earlier.
Fruits can be affected very early in its development. This developing fruit have many lesions with active spots of infection in summer cucurbit production in Florida.
Anthracnose can be also a major problem in post-harvest storage of fruits. Fruits in storage can show characteristic concentric circular pattern which can develop over a few days or weeks.
The fungal pathogen has characteristic whisker-like hairs (setae) which is a key identifiable feature. Among the setae, conidia (spores) can also be seen in affected leaves and fruits.