Transparent Spots on Rose Leaves

Rose Slug

• Sawflies lay their eggs between rose leaf layers. When these eggs hatch, the larvae, or rose slugs, eat away at the leaves of plants. You may spot rose slugs eating foliage at night. These pests are 1/2 to 3/4 inch in length, according to Clemson University Cooperative Extension. Eventually, these pests drop to the soil when it is time to pupate, according to All-American Rose Selections. Your rose garden can experience several generations of rose slugs in one growing year.

Damage

• Rose slugs munch away at the lower and upper layer of leaves. Because they eat in between the veins, you can see transparent spots form on the leaves. The older and larger the rose slug, the more they eat. Entire leaves may be consumed by these pests. The overall health of the rose plant may suffer from lack of leaves. Defoliation inhibits the plant's ability to photosynthesize or produce nutrients. Gardeners may choose to control their rose slug population through cultural management or chemical treatment.

Cultural Control

• Examine the leaves of your rose plants at night for the pests. Bring a flashlight to help you detect rose slugs climbing on leaves. Hand pick rose slugs and place them in a bucket of soapy water. Or, a forceful spray from your gardening hose can knock off rose slugs. Once these insects are on the ground, they cannot climb back up the rose plant, according to Clemson University Cooperative Extension. Unfortunately, one of the downsides of spraying your rose plant at night is that it encourages fungal diseases.

Chemical Treatment

• Treat your rose plant using insecticidal soap. Insecticidal soap can kill rose slugs, but is only effective for 24 hours. Therefore, you may have to repeat insecticidal soap applications. Other chemical measures can be taken with pesticides that contain bifenthrin, carbaryl, cyfluthrin, esfenvalerate, lambda-cyhalothrin, acephate or permethrin, according to Clemson University. Spray both the tops and bottom of your rose plant leaves. Soil drenches containing either dinotefuran or imidacloprid can also be used to kill rose slugs.