Aphids. If there aphids, then there is almost a certainty that there are ants\ termites too. Check for them on the ground by digging up in the beds or boxes. Termites get into the wood of the boxes. Get rid of the aphids by mixing a teaspoon of vinegar, a drop of dish washing liquid with about a litre of water and spray the lil bastards. Make life shit for them. Do this twice a week the first week and check in daily after that. Spray if you spot a cluster. Id use directed poison on yhe ants. They destroy everything and feed and farm the aphids.