Use Reflective or Light-Colored Mulch
Reflective mulches—white plastic or light stones—bounce sunlight up into lower foliage, improving photosynthesis and fruit set on shaded branches. They also deter flea beetles and aphids seeking dark refuge, while conserving soil moisture beneath the pepper canopy.
One year, installing white mulch transformed pepper yields overnight. I watched more blossoms set into pods, and even the occasional ground-nesting bee used the bright ground cover to navigate back to its burrow.