What makes the guave leaves edges brown like this. Is it cold or any thing else?
Guava Plants Leaves
Certified GKH Gardening Expert
It definitely could be the cold, as anything below freezing will start to make it show signs of damage. If this hasn't been the case, then My next guess would be a fungal infection. If it has been very wet lately, then this could be even more possible.
If you think it is likely the latter, then you can apply wettable sulfur to the soil, and it can help clear it up. If it is cold lately, then you can possibly wrap the tree in burlap on those nights.
Here is an article with more information on the care of the tree: https://www.gardeningknowhow.com/edible/fruits/guava/growing-guava-fruit-trees.htm