As a rose gardener, few things are more annoying than finding tiny green worms munching away on the leaves of your prized roses. These little pests are called rose slugs, and they are actually the larvae of a type of wasp called the rose sawfly. While rose slugs won’t kill your plants, they can quickly skeletonize the leaves, leaving behind only the veins. This damage can weaken the plant and make it more susceptible to disease. The good news is that rose slugs are easy to control if you catch them early. Here’s what you need to know about identifying and getting rid of these common rose pests.
What Are Rose Slugs?
It’s no accident that rose slugs look like little green worms crawling on the leaves. They are rose sawfly larvae, which are a primitive type of wasp that doesn’t sting. In the spring, the adult sawfly lays its eggs on the underside of rose leaves. As soon as the eggs hatch, the larvae start eating the leaf tissue. They are light green and grow to be about half an inch long. They move slowly but eat a lot, leaving a web of leaf veins that looks like lace. The larvae feed for three to four weeks and then fall to the ground to pupate in the soil. There is one generation per year.
How to Identify Rose Slug Damage
It’s easy to recognize rose slug damage. Look for windowpane-shaped holes in the leaves where the veins are still whole. Check the undersides of the leaves for tiny green worms. The damage will start low on the plant and move up as the worms multiply. Roses that are already under a lot of stress from drought or not getting enough food will be more likely to get pests. Keep a close eye on your plants in the spring and early summer to catch pests early.
Effective Ways to Get Rid of Rose Slugs
Hand removal
For light infestations limited to just a few plants, hand removal of the larvae is the best organic approach. Check leaves carefully and crush any larvae you find. Drop them into a bucket of soapy water to prevent escape. Repeat monitoring daily until you see no further damage.
Knock them off with water
A strong spray of water from your garden hose will easily remove larvae from leaves. Focus the spray on leaf undersides where they hide. A lot of them will be thrown off the plant by the impact. But make sure to cover the whole plant well.
Insecticidal soap or neem oil
Insecticidal soaps and neem oil can be used to smother and kill larvae on contact while also deterring feeding, Use a dilute solution and spray all leaf surfaces thoroughly Reapply every 5-7 days until you see no further damage, Avoid spraying during the heat of the day as this can burn foliage
Natural predators
Encouraging natural predators like birds, spiders, lady beetles, lacewings and parasitic wasps can help reduce rose slug populations. Avoid using broad-spectrum insecticides that will kill these beneficials. Plant a diversity of flowering plants to attract and provide food sources for these predators.
Row covers
Adult sawflies may not be able to get to plants to lay eggs if there are floating row covers over them. Cover the plants with the sheets early in the spring, before they get hurt. Hold the edges in place and leave the flowers open until they bloom so pollinators can get to them.
Bacillus thuringiensis (Bt)
Bt is a natural bacteria that kills leaf-chewing larvae but is safe for people, pets, pollinators and plants. It must be eaten by the larvae to be effective so thorough application to all leaf surfaces is important. Apply as soon as damage is noticed and reapply every 7-10 days as needed.
Insecticidal dusts
Lightly dusting leaves with diatomaceous earth or neem powder will desiccate and kill young larvae. Focus application on the undersides of leaves where the larvae feed. Reapply after rain or heavy watering. Avoid breathing in the fine dust when applying.
When to Take Action Against Rose Slugs
Monitoring your roses closely in spring is key to effective control. Take action as soon as any damage is spotted. Early intervention can prevent populations from reaching damaging levels. The larvae feed for 3-4 weeks before pupating in soil, so treatment is no longer needed once feeding stops. New infestations may occur in summer if adults emerge from a second generation.
Preventing Rose Slugs Naturally
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Maintain plant health and vigor through proper care and feeding. Healthy roses can better tolerate pest damage. Mulch and prune properly.
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Remove any dropped or diseased leaves from around plants. Larvae may overwinter in leaf litter.
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Turn over soil around plants in fall to expose and disrupt pupae in soil.
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Remove nearby alternate host plants like spirea, pear and apple trees.
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Use row covers in spring to exclude egg-laying adults.
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Attract beneficial insects by planting nectar sources like daisies, asters and parsley. Avoid pesticides that will kill them.
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Hand pick early infestations before they multiply. Crush larvae.
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Monitor daily throughout spring and early summer for early detection.
By taking a proactive and natural approach focused on prevention, you can protect your roses from damage and avoid using any harsh or toxic pesticides. Keep a close eye on your plants, and be ready to take action against the first signs of leaf damage. Employing multiple control methods together will provide the best defense against rose slugs. With diligent monitoring and prompt treatment, you can outsmart these tiny leaf-eaters and enjoy beautiful, pristine rose blooms.
What is rose slugworm?
Rose slugworms are the larvae of a sawfly. Sawflies are a group of insects in the suborder (Symphyta) of the Hymenoptera (bees, ants and wasps). There are about 500 species of
Sawfly are small winged insects, related to bees, wasps and ants. Their caterpillar-like larvae feed on the leaves or fruits of certain plants, including apples, gooseberries and Solomen’s seal.
sawfly in Britain. They have caterpillar like larvae that feed on plant material and are named after the saw-like egg laying organ used by females to lay eggs in plant material. Adults can come in a range of colours many are black, green orange or striped yellow and black. Most are small (<1 cm) but some species such as the Birch sawfly (Cimbex femoratus) can be over 2 cm long. Several species can be found in gardens and are part of the
The variety of living organisms (plants, animals, fungi and microorganisms) in a particular environment. Boosting the biodiversity of your garden has many benefits, including supporting wildlife, improving soil health and reducing the likelihood of pest and disease problems.
biodiversity a healthy garden will support. More information can be found at The Sawflies of Britain and Ireland webpages. Adult rose slugworm have black bodies about 4-5 mm long and two pairs of dusky transparent wings, they emerge during mid May to mid June.
Eggs are laid on the foliage and they hatch into larvae that are black with a slug-like appearance. They are pale yellowish-green with light brown heads. Their bodies are see-through, and the foods they eat can often be seen as a dark green line inside them. The larvae grow to a length of about 10 mm and are somewhat club-shaped with the head end being swollen. When fully fed the larvae go into the soil to pupate.
There are two or sometimes three generations a year between June and October. The second generation in July and August can be the most abundant. Larvae that complete their feeding late in the year overwinter in cocoons in the soil before pupating in April to May of the following year.
This sawfly does not cause any distortion of the foliage and the caterpillars feed exposed on the leaf surface. They are normally found on the underside of leaves but will feed on the upper surface if the plant is shaded.
The larvae do not make holes in the leaves but graze away the leaf surface until only the epidermis remains. Affected areas dry up and become white or pale brown; this type of damage is known as window paning.
Other species of slugworm feed on pear, cherry, lime, oak and willows, these insects are not found on roses.
Rose slugworm can usually be accepted as part of the biodiversity roses support as the damage to a few leaves will not affect the vigour of plants.
- Rose slugworm populations should be tolerated as much as possible, as plants usually grow back from losing their leaves without any effect on flowering.
- In your garden, let birds and ground beetles and other natural enemies of sawflies do their thing.
- Beginning in June, check plants often for larvae and remove them by hand if you can.
How to Naturally kill rid insects Aphids from Roses & Garden DIY
FAQ
How to get rid of small green worms on roses?
If you have a small number of rose slugs on just a few plants, the best approach would be to hand-pick them off and drop them in a cup of soapy water. Another way is to use a strong spray of water from a garden hose. This will kill many of the larvae.
Can you spray vinegar on roses for aphids?
Make a vinegar spray: A vinegar spray can also be effective against aphids. Mix equal vinegar and water in a spray bottle, then spray the aphid-infested plants. Be careful with vinegar because it can harm plants if there is too much!.
How do you get rid of little green worms?
Spray a natural oil based pesticide that prohibits grubs and worms. Mix with a soap also. Also use a cinnamon spray to get rid of any fungus and plant diseases that the worms may spread. Spray it in the morning or evening, don’t spray in direct sunlight or hot time like midday.
Are rose aphids harmful?
Yes, aphids, including those that feed on roses, can be harmful to plants. They feed on plant sap, which can weaken the plant and stunt its growth.