Colletotrichum gloeosporioides: Apparent continuous spore rain may hide local disparities and iterative disease dynamics

Crop diseases are often considered as episodic events associated with specific environmental and weather conditions, but little is known about disease development when conditions for epidemics are sustained in time, as often occurs in the tropics. Colletotrichum gloeosporioides (anthracnose) presence on guava trees was monitored for 45 weeks. Results showed that spore prevalence varied but was consistently present over the period and was greater during the dry than during the rainy season. Secondly, while the general pattern was that of continuous presence of the disease throughout the study area, local patterns on individual trees presented casual peaks that were only partially concomitant, thus suggesting that apparent continuous fungal propagule rain observed in the fields results from distinct repetitive local spore pulses, potentially with asymmetrical contribution from the surrounding vegetation. Local disease dynamics in wild vegetation adjacent to the fields should therefore be more closely investigated in order to clarify its role in crop disease at greater scales such as landscape levels.