Roses are some of the most beautiful, classic garden plants to incorporate into your landscape and are very resilient. However, some pests love rose bushes just as much as we do, and many of these bugs will rip holes in your rose bushes’ leaves, potentially killing the entire plant.
Here are 4 pests that cause holes in rose bush leaves:
- Rose sawflies or rose slugs
- Leafcutter bees
- Japanese beetles
- Rose chafers
So, let’s get to the bottom of who’s been taking chunks out of your rose bush’s leaves. I’ll tell you about the most common pests that eat rose leaves and help you identify which one has been chowing down on your garden.
1. Rose Sawflies or Rose Slugs
Rose sawfly larvae, or rose slugs, are arguably the most common pest in rose bushes. Although called slugs, they are actually caterpillars that will later develop into sawflies.
Adult rose sawflies do not eat rose leaves. Instead, they are pollinators that feed on the nectar of particular flowers. However, rose slugs are a different matter.
The rose slug is green with occasional black spots and a brown, red, or orange head. They are soft and may feel slimy to the touch. If you need more help identifying it, it looks like the Very Hungry Caterpillar from Eric Carle’s classic children’s book.
These caterpillars eat away entire rose leaves. If left to munch, they will create a window-pane effect on your rose leaves, removing the healthy green surface to reveal a brownish “frame” with little holes.
Rose sawfly “slugs” only hatch once a year, from April to May, and they spin their cocoons by the end of June. So, if it is between April and June for you right now, your rose pests might be rose sawfly slugs.
These larvae feed on rose leaves from underneath, where they can dine in the shade. You must examine your rose bush underneath the leaves to detect them.
Removal and Preventive Measures
Pull them off with tweezers or by hand if you find rose slugs. You can toss them far from your rose bush or kill them, depending on how you feel about squashing them.
If you want to prevent a rose sawfly infestation, you can use an insecticidal soap or permethrin-based spray to kill them on contact. However, you should not use these chemicals if you plan to consume any part of the rose plant, such as the hips or petals.
2. Leafcutter Bees
Leafcutter bees are solitary bees that lay their eggs and nest in woody plants and rotten woods. They like to nest in the stems of rose bushes because they harvest small pieces of leaves and construct “cells,” or little containers for their eggs and food, from the leaf fragments.
Adult leafcutter bees leave a noticeable half-moon-shaped hole in the outer edge of leaves. You will recognize it if you see it. The chunk looks like someone has cut a circular hole right in the edge of your rose leaves with a hole punch.
These bees are about the size of a standard honey bee but have blacker bodies with less yellow fuzz.
The actual bees can be tricky to spot. These bees make long tunnels inside wooden structures or in the stems of woody shrubs like roses and seal up the entrances with sawdust, hiding their homes. The best way to detect them is through the circular holes that they leave in your rose leaves.
Eradicating leafcutter bees is challenging, as they do not respond to pesticides.
Treatment and Prevention
To get rid of leafcutter bees, you’ll first need to find the nest. Check the stems of your rose bush and look closely for holes in the woody stems.
If you find a spot, plug it with some wax (candle or cheese wax will do) or some Elmer’s glue (available on Amazon) to trap the female bee and her eggs. Eventually, they will die.
If it seems that the bee has laid a nest somewhere other than in your rose bush, check any exposed wooden structures around your garden. Look for sawdust or holes in the wood. If you find any, seal them up.
You can also prevent leafcutter bees from getting to your rose bush by covering it with a cloth such as a rabbit or cheesecloth. However, since these bees are beneficial pollinators and do not severely harm your rose bush, I rarely recommend this measure since it might block too much sun and inadvertently harm your roses. For most people, eradicating the bees is simply not worth the effort.
3. Japanese Beetles
Despite their beautiful green iridescent shells, Japanese beetles are a bane to gardeners everywhere. These beetles feed on many garden plants, such as roses, grapevines, fruit trees, and bushes. According to the entomologists at the University of Florida, Japanese beetles are a pest to over 300 plant species.
While larval Japanese beetles eat grass roots, the adults fly up on bushes and trees and completely devastate them.
Adult Japanese beetles are around the size of a nickel, and they are easy to spot on the foliage of your plants. They have shiny green heads and brownish wing covers. Shake the plant to determine if Japanese beetles are on your rose bush. If there are any beetles, they should become startled and buzz around a bit before looking for more food.
While the other pests I’ve mentioned are rarely pervasive enough to weaken or kill your rose bush, Japanese beetles can kill your plants. They multiply quickly and eat so much foliage that they can starve your plant of sunlight, ultimately leading to stunted growth, fewer blooms, and, potentially, death.
To eliminate Japanese beetles, you can use one of several insecticides, which include:
- Carbaryl-containing products such as Sevin Dust (available on Amazon)
- Pyrethroid chemicals such as cyfluthrin, bifenthrin, and deltamethrin
- Neem oil
However, one treatment of any of these pesticides will only last three weeks. So, you will need to reapply the insecticide frequently to ward off the beetles.
Traps are also effective for eliminating Japanese beetles. These traps fall into two types — pheromone and food-based traps. Pheromone traps mimic the smell of a female Japanese beetle, so they only attract male beetles. On the other hand, food-based traps attract all Japanese beetles.
4. Rose Chafers
Rose chafers are small beetles with narrow bodies that can either be a brown tan color or iridescent green. Rose chafers primarily eat fruit leaves and flowers, but they are particularly attracted to rose and peony bushes.
Like rose sawflies, chafers “skeletonize” or “window-pane” rose leaves. This eating pattern leaves behind a brown, crispy lattice where the green leaf once was. However, rose chafers will also dine on your rose buds and blossoms, unlike the sawflies.
Rose chafers are so prevalent and voracious that they can jeopardize the health of your plants. They breed quickly and come in full force around May when they heap onto the nearest food source and eat as much as possible.
Their eating habits often deprive plants of the leaves they need to bear flowers or fruit, leaving your rose bush and other plants barren.
However, rose chafers only feed during a four-week breeding cycle that lasts from May to early June in most states, so they are a short-lived pest.
Prevention and Control Methods
To eliminate rose chafers, you can pick them off by hand and drown them in a bucket of soapy water. This manual control is the most effective method if you plan on consuming any of your roses. However, if you only grow roses for ornamental purposes, you can use an insecticide.
Insecticidal chemicals that are effective in eradicating rose chafers include:
- Pyrethroids such as cyfluthrin
You can also drape your rose bush with a cheesecloth or rabbit cloth to deter rose chafers, which is reasonable since they only last for around a month in early spring.