If you are an avid gardener, you know that there are many beneficial insects as well as those that are Rose bush pests. Unfortunately, those that do harm get our attention more readily You must resist the urge to grab a bottle of mega-insect-killer and treat the pests individually, rather than with a scorched earth policy.
Insects are a part of the natural world. As gardeners in general and Rose gardeners in particular, we need to realize that while we can try to control rose bush pests in our gardens, we cannot, nor should we want to, eliminate all insects. Scientists estimate that there are 200 million insects for every human on earth. And all of these insects have a place in the natural cycle, they either eat or are eaten by something, pollinate or otherwise have a symbiotic relationship with other plants or animals, and yes, they sometimes eat what we want them not to.
Major pests of Roses are Japanese beetles, slugs and snails, caterpillars, aphids, mealy bugs, scale and white flies- oh my!
Japanese beetles are a major rose bush pest which have an approximately six week window in July and early August where they are the most destructive. For ways of controlling them, visit our Japanese Beetles web page.
Aphids are tiny greenish to brownish critters that like to suck the life blood out of plants. Fortunately they are easy to see and control by rinsing them off, spraying them with insecticidal soap or controlling them with lady bugs or lacewings.
Cane Borers are the larvae of other insects that like to lay their eggs on the cut end of a rose stem. The borers then eat their way down the stem. Prevention is the easiest way to deter them. Simply coat the freshly cut stem end when you do your pruning with white glue, fingernail polish, wax, tree wound paint, or anything that will coat the end and make it hard for the insect to lay eggs.
Spider mites are opportunistic pests that thrive in hot, dry conditions. They can be controlled by keeping your Roses watered well in dry periods. Neem oil is an organic pesticide that work well against spider mites as well as most of the other pests mentioned herein.
Scale sucks. I mean really, they suck the vital juices out of your roses just like aphids. They usually appear on the stems and look like tiny brown bumps. Fortunately they are easily removed with your fingernail. They may also be treated with dormant or agricultural oil as well as insecticidal soaps.
Slugs like to chew on everything. It’s easy to see the damage they cause to leaves and know that it was them by the slimy trail they left. Slugs are nocturnal and like to hide under things such as your mulch during the heat of the day. There are various products, both organic and inorganic, that all have varying levels of success. The one thing that I see over and over again is to keep shallow containers buried at ground level with beer in them. I’ve never had success with this method and it seems like a waste of good beer also. Trapping them under a board seems to work well. Pick up the board during the day and collect those that sought refuge and dispose of them. I usually toss them in the compost pile to let them work for, instead of against me.
Earwigs are more frightening than damaging. They like to hide during the day in the same places that slugs do, so using the same methods of trapping them may help to control them. They eat both live and dead plant material. If you have infestations of them or they are getting into your home, a soil drench with an insecticide labeled for use on them may be the answer.
Thrips are another sucking insect that attack the ready to open blossoms rather than the leaves and stems. Insecticidal soap can have some effect on them, but watching for damaged buds and removing those that don’t seem to want to open and disposing of them is the best control.
Whiteflies and mealy bugs are closely related to aphids, thrips, mealy bugs and scale. They all feed by sucking sap from the affected plant. The control methods are also similar. Whiteflies are, as their name implies, small white flies. Mealy bugs look like little fuzzy white patches, usually on the underside of leaves.