Not all midges are harmful. Identify your rose's midge before getting rid of them.
Finding pests on roses may or may not be cause for concern. This includes midges. Many species of flying gnat-like insects have been given the common name of “midge.” Some, including the rose midge, are harmful to roses as they eat the flowers and leaves. Some, such as the aphid midge (Aphidoletes aphidimyza), benefit the plant by eating harmful insects, namely aphids. Before taking steps towards getting rid of midges on your roses, you want to first confirm that you do have a harmful species of midge. Treating a plant that has the helpful aphid midge can do more harm than good.
Identifying Rose Midge Damage
The harmful rose midge (Dasineura rhodophaga), looks much like a mosquito as an adult and like the beneficial aphid midge that feeds on aphids. The rose midge eggs, which hatch into white larvae, are laid on the petals and buds. The larvae then eat the tips of the plant. However, if you are not familiar with midges, then the rose midge and aphid midge look very much alike.
Since it can be difficult to identify which species of midge you have on your roses, look for telltale signs of rose midge damage. Rose bushes damaged by the rose midge will have black or brown and withered damaged tips throughout the plant and flower buds will look deformed. The result is a rose plant without any roses or buds. Aphid midges don’t cause damage to the plant. If you have any doubts about the species of midge you have found on your roses, take a sample to your local nursery or university entomology department for identification.
Getting Rid of Rose Midges
For minor infestations, you can control rose midges with natural and organic methods by pruning the tips of the affected plants. For serious infestations, you will have to use insecticides. The University of Minnesota department of entomology recommends acephate or dimethoate insecticides for the control of rose midges. Ortho and Orthene are two brand names that contain acephate. However, when using insecticides the midges can become resistant. Rotate the type of insecticide you use to reduce this risk.
To get rid of rose midges on the plant, you will also need to treat the surrounding soil. The rose midge life cycle also includes the soil under plant as pupa and larva will winter in the soil beneath the plant. Placing plastic sheets on the ground under the rose bushes will catch the pupa and larva that fall from the plant reports the Illinois Natural History Survey Prairie Research Institute. When using insecticides, you need to also treat the soil. Some gardeners remove the mulch surrounding the plant during the winter to remove any wintering rose midges.
Preventing Rose Midges
To prevent introducing rose midges to your rose garden, Oregon State University recommends buying bare root roses or removing all the soil and rinsing the roots before planting new rose plants. This will help remove any larva or pupa that could be found in the soil surrounding the roots.
The rose midge fortunately is a rare pest on roses, with minor outbreaks having occurred along the west coast, mostly in Washington and Oregon, and a few cases in California.