I live in SE Asia and recently bought a house with guava trees. The leaves have some kind of disease I can’t seem to identify.

Question

Maybe you can identify and suggest a remedy. Please note the three pictures below taken today.

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Answer 1

This appears to be "edema", an environmental and physiological disorder related to water uptake and retention, and not a pest or disease issue.

Your case is extreme and rather unsightly, but there is no cure needed or available, except as the following article suggests, soil and water management is important.

https://www.gardeningknowhow.com/plant-problems/environmental/treating-edema-in-plants.htm

http://trecclinic.blogspot.com/2009/11/disease-of-month-physiological.html

http://ucnfanews.ucanr.edu/Articles/Science_to_the_Grower/SCIENCE_TO_THE_GROWER__edema_on_plant_leaf_/