Elderberry plants contain a very sweet-tasting sap that many insects are attracted to. For this reason you will want to inspect your plants every week or two and take appropriate measures if insects begin to pose a problem. There are several insect spray that can be used on elderberry plants, but one of the best is also non-toxic to humans. It's called Bonide All Season's Spray Oil.
Don your gardening gloves and inspect your elderberry plants for rotting fruit and dead and rotting leaves or branches. Remove and discard any rotting fruit or leaves or branches as these attract insect pests.
Inspect your plants for insect pests. If pests are found go to your local nursery or home improvement center and purchase a bottle of Bonide All Season Spray Oil or another non-toxic insecticide or insect repelling soap that is recommended by your nurseryman.
Fill a spray bottle with your insecticide. From a distance of approximately 6 inches spray your elderberry plants until the leaves are damp and even dripping slightly. Do not rinse the spray off; Bonide sprays are safe to leave on fruits and leaves.
Inspect your plants on a weekly basis and re-spray as often as necessary.
Continue to remove any dead or rotting fruit or vegetable matter.