The whitish lumps of gum-like substance on the shrub stems are wax covering the bodies of a pest called Indian Wax Scale: https://extension.umd.edu/resource/soft-scales-trees-and-shrubs

Manual removal of all adults that you can find is the best first step, even though it can be tedious on a dense or large shrub. Spraying what's left is one option, and pruning-out heavy populations is another, though only for shrubs which rebound well from drastic pruning. (Holly, boxwood, and a few other evergreens fit into this category.) If this is a shrub known to be an invasive species, like Burning Bush, we suggest removal entirely and instead replacing it with a different species.

Topical sprays are easiest to apply in the dormant season (winter), though you can use horticultural oil later this summer (make sure the product isn't "dormant oil," which is too concentrated to use now). As with any pesticide, follow label instructions about how often sprays can be made, since more than one application may be needed. "Crawlers," the most vulnerable stage of a scale's life, don't appear for this species until around the window of mid-June  to mid-July (weather depending), so topical treatments aren't practical until that point because the adults are too well-protected by their wax. Otherwise, systemic treatments may be more effective and efficient at knocking-down their numbers, and can probably be applied earlier (this may vary from product to product) but the ingredients able to control this pest in this way need to be applied by a certified pesticide applicator as they are not available or permitted for homeowner use.

Miri