Rose slugs on knockout roses

How to Get Rid of Rose Slugs

If you have a garden or flower bed and notice holes in your rose leaves, it is likely that you have rose slugs. Despite their name, rose slugs aren’t a slug at all and are more closely related to caterpillars. Rose slugs like to feed on the leaves of rose shrubs, so if you are growing roses, your flowers could be at risk.

Rose slugs are a prominent issue that pops up in mid to late summer and often the damage done to the rose leaves are mistaken for a disease or some other issue because the rose slug is not seen. This is usually due to the rose slug being very tiny and green so it can blend into the leaf and go unnoticed. These bugs can kill your rose bush if you do not intervene.

If you are dealing with a rose slug infestation and damage to your roses, read on to find out what you should do to get rid of the pest.

Identification

There are three types of rose slug: one is a yellowish-green larvae with brown head, the other is green larvae with bristles on its body, while the third is curled up slug that coils behind the leaves. They are very small in size ranging from a 1/2 inch to 3/4 inch in length max. These larvae are the early lifecycle stage of plants eating wasps called Sawflies. These slugs stay on the underside of the leaves.

Inspection

Where To Look

Focus your search in areas where your garden plants, flowers and vegetation are in your yard. Rose slugs chew off the leaves of the rose and cause defoliation of the rose plants and decay on the foliage of the leaves. The curled up rose slugs curl up into a coil under the leaves and chew holes into the rose leaves, removing the soft tissue of the leaves which results in the leaf looking scorched and brown.

What To Look For

You’re going to be looking for plant damage and holes in your rose leaves. These are going to look like large holes that go through the leaf or little brown spots that look like a plant disease but is actually the tiny underdeveloped rose slugs that are too small to eat all the way through the leaf.

Treatment

By far the single most effective method of dealing with damaging rose slugs destroying your plants is insecticides The trick is to use products that are effective in killing rose slugs but also can be safely sprayed on plant life without harming the plants. This is why our experts recommend Dominion 2L.

Step 1 – Apply Dominion 2L Insecticide

Dominion 2L insecticide that contains the active ingredient imidacloprid which is known to be lethal to insects like rose slugs while also being easy on plants. It also works systemically meaning it can be applied to the soil and be taken up into the root system of the plant to protect against the plant against rose slugs. You can safely spray around your garden, lawn, flowerbeds and trees without an issue.

For soil treatments, start by mixing 0.46 to 0.6 fl. oz. of Dominion 2L in a sprayer with 1 to 2 gallons of water and apply as a broadcast treatment and mix into the soil. As a foliar application, mix 1.5 oz. per 100 gals of water in a sprayer of your choice and then apply to your rose bushes, flower beds and garden plants using a fan spray nozzle setting, making sure to also get the underside of the leaves since that is where rose slugs like to hide. Spray Dominion 2L every 2 to 3 months for continued control.

Prevention

To keep rose slugs away from your flowers and garden, a quarterly preventative treatment of Dominion 2L will suffice. Aside from this, we also have a few additional tips.

Picking the rose slugs

Use tweezers or some other device and wear gloves while plucking or picking the larvae out of the rose leaves and dispose of them in solution of insecticidal soap. This will curb the infestation of the rose slugs and limit the damage that will be caused to your rose plants.

Water hosing the rose slugs

Use a water hose over the rose plants. Use the valve with pressure and open the water hose and wash away the rose slugs. The pressure of the water will let the slugs fall off the leaves. You can pick them and spray insecticidal soap over the slug to dehydrate and kill them. The pressure of the water will also kill a few of the slugs. Use 3 tablespoons of insecticidal soap with 1 quart of water and spray it direct on the rose slugs that have fallen down. It will kill the larva immediately and control the infestation on the rose plants. A bug blaster can be used, it is a special device that creates a wall of water and the jet of water comes with pressure eradicating the rose slugs from the leaves.

Tending to the roses

Keep the roses fresh and clean. Make sure to prune and remove all decayed leaves surrounding the rose plants itself. The removal of decayed leaves will ward away the rose slugs. Taking care of the soil, applying fertilizer and other treatments that roses need will keep the sawflies away.

Key Takeaways

  • Rose slugs are the larvae of sawflies and are known to have a big appetite for rose leaves in gardens and flowerbeds and can do a lot of damage if there is no intervention.
  • We recommend spraying Dominion 2L on your plants and in your garden soil to kill rose slugs and end the infestation.
  • To prevent rose slug re-infestation, spray Dominion 2L every 2 or 3 months for continued protection and control and tend to your rose garden regularly.

Oil spray is best bet for combatting rose slug

Q: I hope you can help me with a pest that is chewing up my roses. It is a small, caterpillar-like animal. I was told it is not a caterpillar but a crawler and thus does not react to BT. This seems correct. Have you any remedy?

A: There are two species of rose slugs, and I suspect that one of them is eating your rose leaves. Both are like caterpillars. The rose slug is velvety green or yellow-green, while the bristly rose slug is light green with, unsurprisingly, rather stout bristles. They both crawl on the undersides of leaves and eat between the veins, turning the leaves to lace. The bristly rose slug may also eat chunks of leaves, veins and all.

The clincher in distinguishing between the two is that the rose slug has only one life cycle — in spring — while bristly rose slug will reproduce several times in the warmer months. Therefore, if the problem is gone by summer, you have rose slugs, whereas if you still see new damage in mid- to late summer, you have the bristly sort.

Rose growers sometimes ignore light infestations of either, letting natural predators, such as birds and parasitic wasps, keep them in check, but if the pests become too numerous, they can defoliate your roses in their growing season — once, if you have rose slugs, and several times with bristly rose slugs.

In such severe cases, summer oil sprays are a good control choice, since they spare predators. Spray for rose slug in spring as soon as the rose is in full leaf. At this time the larvae hatch from eggs laid in the soil under the plants and climb to the leaves. Spray again if you see damage. Spray for bristly rose slugs early also, and repeat often through summer as long as you see damage.

Bristly rose slugs lay eggs in slits in the upper side of leaf midribs. This means that if you defoliate the plants when you prune them, as many rose growers do, to encourage dormancy, you will be removing the eggs. Be sure to clean up fallen leaves as well.

You have probably been wondering about the names of these creatures. They do resemble their molluscan namesake, but in truth, they are the larvae of insects called sawflies. (Some sawfly larvae look even more sluglike than rose slugs; for example, the pear slug, which does a good imitation of a black slug.) Sawflies are stingless relatives of bees and wasps, and though the larvae may damage plants, in their adult stage many kinds of sawflies are useful as pollinators.

Q: I read your article on getting rid of katydids, but wonder if the same organic garlic spray will help with the infestation of spit bugs in my many lavender and rosemary plants, as well as in the wildflowers I have been planting over the past 10 years. I live in Inverness on 5 mostly wild acres in a house surrounded by lavender and rosemary.

This year the spit bugs have come in a profusion I have not seen in nearly 30 years. I’ve tried the usual, hosing them off for about a half hour every day. They disappear for a half day, only to reappear by evening. I bought Safer soap and a hand sprayer and carefully blasted every plant twice a day. That seemed only to encourage them.

I have been told that spit bugs don’t harm plants, but the local garden club experts say they actually do harm lavender. I have spent 10 years propagating these plants and carefully tending them, thus don’t want anything to harm them. Please advise soon as my New York daughter is bringing friends to stay for a week in mid-July, and I would like to have them disappear before then.

A: Spittlebugs, technically speaking, do harm plants by sucking some of their sap, but most plants can tolerate a little of this damage and still thrive. Their feeding causes some kinds of plants, such as parsley, to become misshapen, which doesn’t make it less edible, but does reduce its culinary appeal. Farmers ignore light to moderate spittlebug infestations, considering a spray for them more trouble and more environmentally disruptive than it is worth.

The white foam the insects use for protection is unattractive; many gardeners try to get rid of them. Spraying with water is probably about as effective as using soap spray, since the insect in the “spittle” is a nymph, an immature creature, that may lack the strength to reclimb the plant, and also is often injured by the water.

However, more spittlebugs appear all spring, largely because the spittlebug eggs, which were laid on the plants in late summer, continue to hatch. The good news is that the spittlebugs should be gone by mid-July no matter what you do, since they have only one generation a year. By then they will all be froghoppers, small jumping insects similar to leafhoppers. The adults cause little damage.

Anything you do to remove plant material in late summer or fall will reduce the number of eggs that will be present to hatch next spring. Start by correctly pruning your perennials. Cut your spent lavender flower stems down to the place where you see two side shoots forming. Shape and thin your rosemary by cutting the longest stems to a joint with another stem. (Be careful not to cut into any part of rosemary stems that don’t have leaves, though, as they won’t regrow.) Mow any nearby weedy areas. Donate all of your cuttings and mowings to municipal composting programs that can compost them at a high enough temperature to kill insect eggs.

I don’t know if the garlic oil spray I described in my May 31 column would repel these insects. If you want to try it, do so in mid- to late summer to discourage the laying of eggs. Leave an area untreated so you can tell if the spray helped.

Finally, spittlebug predators include predatory wasps and tachinid flies. These can be encouraged to feed in your garden by having flowers they like in bloom at spittlebug hatching time, like tidy tips (Layia platyglossa) and California coffeeberry (Rhamnus californica).

Rose Bush Slugs

As the weather finally warms up the bad bugs show up. The rose slug skeletonizes leaves on roses. Several of our customers mistook the damage for a disease. Rose slugs look more like caterpillars than slugs. They are the larvae of primitive wasps called sawflies. There are three species: the bristly rose slug (Cladius difformis), the European rose slug (Endelomyia aethiops), and the curled rose slug (Allantus cinctus). The larvae of all three are light green with brownish- orange heads, and they range in size from 1/2 to 3/4 inch long. The bristly rose slug is usually covered with many short hairs, while the other two species are smooth. When fully grown, rose slugs closely resemble butterfly or moth caterpillars. Larger, older rose slugs chew holes right thru the leaf. Female sawflies (the adult life stage of rose slugs) lay individual eggs in slits along the margins of leaves. When the larvae hatch they begin feeding on the leaf. Once they are fully grown, they drop to the ground and pupate in cocoon like chambers in the soil, then emerge as sawflies. Depending on the species, there can be one too many generations each year — one for the European rose slug, at least two for the curled rose slug, and six for the bristly rose slug.

Rose slugs are extremely hard to see as their green color is almost the same as a rose leaf. Remember I always preach “Early Protection is the Key to Preventing Plant Problems”. When you first notice a problem with a plant address it before it becomes overwhelming! Rose slugs can defoliate a plant quickly.

Conventional Treatments

Bonide Eight Insect Control

Organic Treatments

Dr. Earth Pro-Active™ Home & Garden Insect Spray

Formulated with essential oils and garlic extract to knock down and kill insects quickly, the results are apparent from immediately to several minutes. Dr. Earth Pro-Active™ works to block Octopamine neuroreceptors. Octopamine is a chemical neurotransmitter that controls body movement and metabolism in insects and mites. The ingredients in Dr.Earth Pro-Active™ interefere with the transmission of Octopamine signals throughout an insect’s body. The interference of these signals leads to metabolic toxicity, immobilization and ultimately death. Garlic extract has been proven to repel insects for several weeks or longer.

Bonide Rose Rx 3 in 1 RTU

Two way triple action: Insecticide – Miticide – Fungicide/Kills eggs, larvae and adults! Prevents and controls black spot, anthracnose, rust, scab, blights—stops powdery mildew in as little as 24 hours! Kills all life stages of aphids, mites, scale, whitefly, beetles, leaf rollers—For use on roses and flowers as well as fruit, nuts, vegetables, herbs, spices, houseplants, trees and shrubs. May be used indoors. Easy on beneficial insects. An excellent choice for organic and IPM gardens. Contains NEEM OIL organic insecticide. Approved for organic gardening.

Posted in: Summer | Tags: Pests, Roses

Rose Slugs – Shrubs

Back to Insects/Mites-Shrubs


Immature rose slug on leaf

The rose slug is one of three common sawflies that attack roses (others are curled and bristly rose slugs). Adults of all three species resemble wasps and are about 1/4″ long. Mature larvae are about 1/2″ long and yellow-green with yellow heads. The larvae skeletonize the leaves and in heavy infestations can cause leaves to turn brown and curl. Check roses in May and June (in Maryland) for the slug-like, greenish-yellow larvae on the upper surface of skeletonized leaves. However, rose slugs can be active through the fall. If the infestation is light, pick off and destroy the larvae. To control heavy infestations, use horticultural oil or spray with spinosad. Target the undersides of the leaves.
Bristly rose slug larvae are about 5/8″ long and greenish white with long, stout bristles. They skeletonize leaves by feeding from the undersides of the leaves and later chew holes through the leaves. Curled rose slug larvae are metallic green above, marked with white dots, grayish white underneath, with yellow-brown heads. They curl up like a cutworm and are about 3/4″ when mature. Curled rose slugs initially feed by skeletonizing the leaves, but eventually defoliate entire leaflets except for the largest veins.

Bristly rose slug larvae are about 5/8″ long and greenish white with long, stout bristles They skeletonize leaves by feeding from the undersides of the leaves and later chew holes through the leaves

Coiled rose slug Rose slug damage on bud

Defoliated rose

Slugged Rose Leaves

Roseslug sawflies (order Hymenoptera, family Tenthredinidae) were once generally considered only nuisance pests of roses in Ohio. The Common Roseslug Sawfly (Endelomyia aethiops) (a.k.a. Rose Skeletonizer) was most often encountered followed occasionally by the Curled Roseslug (Allantus cinctus). The common roseslug has only one generation and the curled roseslug two generations. These sawflies would come and go so quickly they seldom caused appreciable damage.

However, in recent years, these relatively innocuous sawflies have been largely supplanted in Ohio by the more damaging Bristly Roseslug Sawfly (Cladius difformis) which has multiple generations per season. Damage from this sawfly starts in the spring and only ends with the first frost. The expanding numbers with each new generation may produce heavy defoliation by the end of the season.

I found symptoms yesterday on hybrid tea and Knock Out roses in southwest Ohio that was consistent with damage caused by a roseslug sawfly; however, I could not find any larvae to make a positive identification. The culprit could have been the common roseslug and they have completed their development for the season. Or, the damage could have been produced by curled or bristly roseslugs and we are in between generations.

Early instar roseslug larvae feed by removing one leaf surface and the mesophyll beneath. The corresponding epidermis on the opposite leaf surface remains intact and turns white producing a characteristic “windowpane” symptom. Eventually, the “windowpanes” drop out to produce holes. Later instars feed between the main veins to directly produce holes in leaves. Heavy feeding damage by early and late instars may combine to produce “see-through” leaves. We have commonly observed this type of damage from bristly roseslugs over the past few years in southwest Ohio.

You must look closely to spot the pale green semi-transparent sawfly larvae. Despite their common name, the larvae of roseslug sawflies resemble tiny caterpillars and look nothing like the glistening, elongated pear-shaped “slug sawflies” which do resemble tiny slugs. As their common name indicates, bristly roseslug sawfly larvae are covered with short, hair-like bristles that can be best seen with a hand-lens.

Control and prevention of further damage depends on a proper identification of the roseslug culprit. Only the bristly roseslug is worthy of control measures because it continues to produce damage throughout the season. Biorationals such insecticidal soaps are effective, but direct contact is necessary. Products containing spinosad (e.g. Conserve, Entrust) are effective against sawfly larva and will also have less impact on bio-control agents. Chlorantraniliprole (e.g. Acelepryn) is also effective and presents a low risk to pollinators. Soil drench applications of systemic insecticides such as imidacloprid (e.g. Merit) or dinotefuran (e.g. Safari) are effective and provide lengthy protection. Although roseslug larvae look like caterpillars, products based on strains of the bacterium Bacillus thuringiensis (Bt) that are specific to controlling moth caterpillars (order Lepidoptera) will have no effect on these primitive hymenopteran larvae.

Rose Insects & Related Pests

With their showy and often fragrant blooms, roses are easily one of the most popular flowering plants grown in South Carolina. Unfortunately, the numerous insects and related pests that attack them can make growing them “interesting”, if not outright challenging. As with any plant, the first priority should be to provide the rose with the cultural conditions that it requires. A vigorously growing rose is much more likely to survive pest damage than a stressed plant. For more information on the cultural requirements of roses, see HGIC 1172, Growing Roses and HGIC 1173, Pruning Roses. For information on diseases of roses, see HGIC 2106, Rose Diseases.

When trying to control insects and related pests on roses, it is essential that the plants be thoroughly inspected on a regular basis. These inspections increase the likelihood that a pest infestation will be detected early, when pest numbers are low and control is easiest. In order to choose the best control method, it is necessary to correctly identify a pest first. Often, more than one control option is available for a pest. Whenever possible, physical control measures should be tried first. If a chemical control is necessary, the least toxic chemical should be used, being sure to apply it when a susceptible stage of the pest is present. When applying a pesticide, thorough coverage is important. Always be sure to read the pesticide label before purchasing. Apply all pesticides according to label instructions, following all precautions.

Aphids

Various species of aphids feed on roses, but the predominant species is the rose aphid (Macrosiphum rosae). Rose aphids are small (about ⅛ inch long). They are soft-bodied, pear-shaped, pink or green insects that are found in clusters on new growth of buds, leaves and stems.

Rose aphid (Macrosiphum rosae) infestation on leaves of hybrid tea rose.
Anne W. Gideon, www.insectimages.org

Aphids feed on plant sap with their piercing-sucking mouthparts. A low population of aphids does little damage to a rose bush; however, aphids reproduce very rapidly and can quickly reach numbers that cause damage. Their feeding results in distorted growth. Heavy infestations can reduce the number and quality of blooms. As they feed, aphids excrete honeydew, a sugary substance that attracts ants and wasps. The honeydew supports the growth of unsightly, dark-colored sooty mold fungi on the leaves.

Control: Aphids have several natural enemies, including parasitic wasps, ladybird beetles (ladybugs) and larvae, and green lacewing adults and larvae. Their natural enemies tend to keep aphid populations under control except in cool weather. Ants are sometimes associated with aphid infestations and will protect them from their natural enemies. If ants are present, they should be controlled.

Aphids can be hosed off with a strong stream of water directed above and below the leaves. Spraying with water should be repeated frequently as needed, focusing in particular on new growth. Roses can also be sprayed with insecticidal soap to control aphids. Insecticidal soap must be sprayed onto the aphids to be effective. Repeat spray three times at 5 to 7 day intervals. Higher toxicity insecticides are available. However, it is important to note that aphids are very difficult to control because they multiply so rapidly. Leaving even one aphid alive can result in a large population very quickly. In addition, these insecticides kill the natural enemies of rose aphids.

If insecticides are deemed necessary, the following are available in homeowner size packaging. Sprays containing bifenthrin, cyfluthrin, horticultural oil, lambda cyhalothrin, malathion, neem oil, permethrin, or pyrethrin will control aphids. Soil drenches or granular applications of imidacloprid or dinotefuran will control aphids and last longer within the plant to prevent future infestations. See Table 1 for products containing these insecticides.

Beetles

A number of different beetle species feed on roses. Many of these beetles feed mainly on flower buds or open blossoms, but can feed on leaves. Since many beetles feed mainly at night, the gardener rarely sees them, only the damage that they cause.

Japanese beetles (Popillia japonica) with characteristic damage of leaf skeletonization.
David Cappaert, Michigan State University, www.insectimages.org

Japanese beetles (Popillia japonica) feed during the day and are perhaps the most readily recognized of the beetle pests that feed on roses. An adult Japanese beetle is about ½ inch long and has a metallic green body and legs with coppery-brown wing covers. It can be distinguished from similar beetles by the tufts of white hair that are clearly visible at the end of its abdomen.

The adults begin emerging from the soil in mid-May and are present through August. They can live from 30 to 45 days. They lay their eggs in the soil. Grubs hatch from the eggs and feed on grass roots. As the weather cools, the grubs move more deeply into the soil to overwinter (survive the winter). In the spring, the grubs migrate back up to the root zone and continue to feed. They pupate (change to adult form) in late April and May.

Japanese beetles have chewing mouthparts and feed on flowers, buds and leaves of roses (as well as numerous other plant species). Partial or entire flowers and buds may be eaten. Typically, flowers and buds that have been fed on have ragged edges and/or holes in the petals. Affected buds may fail to open. Rose leaves are typically skeletonized (only leaf veins remain) by the feeding. Leaves with tender veins may be eaten completely.

Control: Various non-chemical control options are available for Japanese beetles. They can be handpicked and destroyed by dropping into soapy water. When only a few plants are involved, fine netting, such as tulle fabric, can be placed over the bush or individual blossoms to exclude the beetles. Japanese beetle traps are available commercially, but should be used with caution. They can be effective at reducing adult populations, but they should be kept at least 50 feet from the plant(s) that you are trying to protect. The traps have the potential to create more of a problem by attracting numerous beetles to the area. Also, traps must be emptied frequently as beetles are repelled by the smell of ammonia which is released by dead, rotting beetles.

Numbers of adults may also be reduced by using the product, Milky Spore, against the grubs in the lawn. This product contains a disease-causing bacterium (Bacillus popilliae) that specifically infects the grubs of Japanese beetles. It is applied to turf and once established, can be effective for 20 to 30 years. However, as the adults are strong fliers, they can fly in from nearby lawns and pastures.

It is important to keep in mind that rose blossoms openly quickly and are very attractive to Japanese beetles. These circumstances make it difficult to keep the blooms adequately covered with insecticide to protect them. Insecticides that are labeled for homeowner use include sprays containing bifenthrin, cyfluthrin, lambda cyhalothrin, neem oil, permethrin, or pyrethrin to control beetles. Soil drenches or granular applications of imidacloprid or dinotefuran, will control Japanese and other beetles and last longer within the plant to prevent future infestations. See Table 1 for specific products.

Mites

Mites are not insects but are more closely related to spiders with eight legs as adults instead of six. They are extremely small (about 1/50-inch long) and are somewhat difficult to see without a magnifying lens. One way to detect them is to hold a piece of white paper under a branch and then tap the branch sharply. Wipe your hand over the paper. If mites are present, red streaks will be seen.

Two-spotted spider mites (Tetranychus urticae) and southern red mites (Oligonychus ilicis) are pests on roses in South Carolina. Two-spotted spider mites are more of a problem during hot, dry weather and susceptibility increases when a rose is drought stressed. Southern red mites are more of a problem during cool weather in spring and fall, and their populations drop during summer.

Spider mite (Tetranychus urticae) webbing and plant injury.
Clemson University – USDA Cooperative Extension Slide Series

Mites have piercing-sucking mouthparts. They suck plant sap, typically feeding on the lower surface of a leaf. Early damage is seen as yellow or white speckling on the leaf’s upper surface. Fine webbing may be seen on the undersides of leaves. With severe infestations, leaves may develop a grayish green or bronze color, and webbing may cover both sides of leaves as well as branches. Severely infested leaves may drop prematurely. Webbing can collect dust, making the plant look dirty.

Control: Both beneficial insects, such as lacewings and lady beetles, and predatory mites prey on spider mites. Predatory mites are about the same size as spider mites but can be distinguished from spider mites by their long legs and the speed with which they move. Several species of predator mites are available commercially for use as biological control agents.

A strong spray of water is a non-chemical control option that removes eggs, larvae (six-legged immature stage), nymphs (eight-legged immature mites) and adult mites. Be sure to spray lower surfaces of leaves and repeat as needed. This method is most effective with light infestations as seen with early detection. An important advantage of this control method is that populations of natural enemies are not harmed.

Insecticidal soaps and horticultural oils are effective control options for spider mites, and are essentially nontoxic to humans, wildlife, and pets, and only minimally toxic to beneficial predators. When using these products, good coverage is critical to ensure contact with the pest, and reapplication may be needed as determined by follow-up monitoring for the pest. Foliar injury from soaps and oils may occur on plants under drought stress. Water the plants well prior to spraying. Do not spray with soaps or oils if the temperature exceeds 85 degrees, and always spray in the evening to slow drying time of the soap or oil.

When growing roses, the use of broad-spectrum insecticides should be avoided as much as possible as these products can kill off natural enemies that help keep spider mite populations in check. Also, avoid pesticides that claim to “suppress” mites as they tend to be weak miticides. When stronger chemical control is needed, the following insecticides/miticides are available in homeowner size packaging: tau-fluvalinate or bifenthrin sprays. See Table 1 for examples of brands and products.

Thrips

Various thrips species feed on roses. Two of the most common are flower thrips (Frankliniella tritici) and western flower thrips (F. occidentalis).

Adult female thrips of both species are tiny, yellowish-brown insects with fringed or feathery wings. At less than 1/16-inch long, they are barely visible without a magnifying glass. However, blowing lightly into the blooms and leaves causes thrips to move around, making them easier to see.

Thrips (Frankliniella sp.) damage on roses.
Clemson University

Both immature and adult thrips feed by scraping surface cells to suck plant sap. They feed on both leaves and flower petals with the majority of their damage to roses occurring from early to midsummer. Their feeding may result in distorted buds that open only partially or abort prematurely. Feeding on petals may result in petals streaked with silvery-white or brown as well as petals with browning edges. White and light-colored rose blossoms appear to be particularly attractive to thrips. Young leaves may be distorted and flecked with yellow as a result of thrips feeding.

Control: Control of thrips is difficult. Infested rose blossoms should be removed and destroyed. Grass and weeds in the area should be kept mowed or removed when possible. Insecticides are available but timing of sprays is very important. They must be applied before thrips enter unopened buds. In addition, because rose blooms expand rapidly, it is difficult to keep them adequately covered with insecticide. If it becomes absolutely essential to spray an insecticide, the following are available in homeowner size packaging: acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, permethrin, or spinosad. Insecticidal soaps will help control thrips, but thorough coverage is necessary. The soap spray must contact the pest to be effective, and may require three sprays at 5- to 7-day intervals. Soil drenches or granular applications of dinotefuran or imidacloprid will give thrips suppression. See Table 1 for examples of brands and products.

Rose Scale

Adult scale insects have an unusual appearance. They are generally small and immobile, with no visible legs. They secrete a waxy covering, making some appear white and cottony while others appear like white, yellow, brown or black crusty bumps. The waxy covering or “scale” protects adult scale insects from many insecticides. Their immature forms, called crawlers, are susceptible, however.

Adult rose scale (Aulacaspis rosae) on a rose cane.
U.S. National Collection of Scale Insects Photographs Archive, USDA ARS, www.insectimages.org

Several species of scale are pests of roses, but rose scale (Aulacaspis rosae) is one of the most serious. Female rose scales are round, gray to white and about 1/16-inch long. Males are elongate, white and much smaller than females. These insects overwinter as eggs under the waxy covering of the mother.

Rose scales are usually found on rose canes where they feed on sap with their piercing-sucking mouthparts. With a heavy infestation, rose scale can cause cane decline or twig dieback.

Control: Various natural enemies, including ladybird beetles (ladybugs) and parasitic wasps, usually keep scale insects under control. With light infestations, scale can be scraped off by hand and destroyed. Pruning out and destroying heavily infested canes is helpful. Horticultural oil sprays (also called supreme, superior or summer oils) work well to control armored scales, such as the rose scale, by penetrating their waxy covers and smothering them. Horticultural oils applied at higher rates of 3% to 4% during the dormant season (i.e., to a rose bush that has lost its leaves) will penetrate the thick waxy covers of the overwintering adults. Applications at lower rates of 1% to 2% can be used during the spring to target the crawlers (immatures) and the newly settled scales with thin waxy covers. It is best to spray when temperatures are between 40 and 85 degrees.

Monitor the crawler emergence in the spring with sticky cards, double-faced tape wrapped around a branch, or by putting an infested shoot into a baggie and watching for crawler movement. The presence of crawlers can sometimes be determined by sharply tapping an infested twig on a piece of white paper. Crawlers are very small and will appear as moving specks of dust.

Avoid using insecticides as much as possible as they will often kill the naturally occurring enemies of scale. When insecticides are necessary, they should be applied only when the crawler stage is present. The following insecticidal sprays are effective against crawlers only: acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, malathion, or permethrin. Soil drenches of imidacloprid do not control these armored scales, but soil applications of dinotefuran will give good control.

Rose Leafhopper

Adult rose leafhoppers (Edwardsiana rosae) vary in color from white to gray to yellow to green. They are wedge-shaped and between ¼- to ½-inch long. When a plant is disturbed, they hop or fly away quickly.

The adult female deposits eggs within the bark of rose canes in the fall. Dark, purple, pimple-like spots on the bark indicate the presence of eggs. In the spring, the young nymphs (immature forms that resemble adults but are wingless) emerge from the cane. The wounds that remain in the bark as they emerge, as well as wounds made during egg-laying, can provide openings for stem canker-causing fungal pathogens to enter. Stem canker can result in plant death.

Nymphs and adult leafhoppers feed on the undersides of leaves, using their piercing-sucking mouthparts to suck plant sap. Their feeding causes white stippling (small dots) on the upper surface of the leaf. The stippling spots may merge, causing leaves to appear almost white. Damaged leaves may drop prematurely. Between feeding by the nymphs and adults, and egg laying by adult females, a severely infested rose bush may be killed.

Control: Natural enemies of rose leafhoppers include damsel bugs and assassin bugs. As such, broad spectrum insecticides that may kill these beneficial predators should be avoided. When an insecticide is necessary, be sure to spray lower leaf surfaces thoroughly. The following insecticidal sprays are effective against rose leafhoppers: acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, malathion, or permethrin. Soil drenches or granular applications of dinotefuran or imidacloprid will suppress leafhopper populations. See Table 1 for specific products.

Rose Slugs

Rose slugs are the larvae (immature forms) of sawflies, non-stinging members of the wasp family. Three species of sawflies, the roseslug (Endelomyia aethiops), bristly roseslug (Cladius difformis), and curled rose sawfly (Allantus cinctus), are pests of roses. The larvae of some sawfly species are hairy and often mistaken for caterpillars. Others appear wet and shiny, superficially resembling slugs. The larvae generally reach about ½-to ¾-inch in length.

Rose slug feeding on leaf surface.
John A. Weidhass, Virginia Tech, www.insectimages.org

Generally, rose slugs feed at night. Depending on the species, young rose slugs feed on the upper or lower surfaces of leaves between veins, leaving a ‘window’ of translucent tissue that turns brown. As some species of rose slugs get larger, they chew large holes or the entire leaf with only the midrib remaining. Regular inspection of roses is important because feeding typically progresses quickly and extensive leaf skeletonizing can occur if infestations are not noticed. In addition, with their coloring, they can be very difficult to spot on leaves.

Control: Rose slugs can be controlled by handpicking. They can also be removed by spraying with water. Once dislodged, they cannot climb back onto the plant. Insecticidal soap and horticultural oil are also effective against rose slugs. Other insecticidal sprays that are labeled for homeowner use include acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, permethrin, or spinosad. Sprays should thoroughly cover both upper and lower leaf surfaces. Soil drenches or granular applications of dinotefuran or imidacloprid will control sawfly larvae. Bacillus thuringiensis will only control true caterpillars and not the larvae of sawflies. See Table 1 for examples of brands and products.

Leafcutting Bees

Leafcutting bees (Megachile species) are similar in size to honeybees, but are a blackish or metallic purple or green color. The females cut out semi-circular sections of leaves, which they use to line their nests. The cut surface is very smooth as compared to the ragged edge that results with most leaf feeding insects.

An unusually severe leaf cutting injury to wild rose by leafcutting bees (Megachile sp.).
Whitney Cranshaw, Colorado State University, www.insectimages.org

Control: No control is recommended because the damage caused by leafcutting bees is minimal, and the bees are important as pollinators.

Caterpillars

Infrequently caterpillars (immature stage of moths and butterflies) will be found feeding on rose foliage. Damage will appear as holes or irregular-shaped areas of the leaf blade that have been eaten. Several caterpillars may feed upon rose foliage, including the corn earworm, eastern tent caterpillar, stinging rose caterpillar and puss caterpillar.

Control: Insecticidal sprays of Bacillus thuringiensis, acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, malathion, neem oil, permethrin, pyrethrin, or spinosad will control caterpillars. See Table 1 for examples of brands and products.

Grasshoppers

Grasshoppers are general feeders that feed on the foliage of many kinds of plants.

Control: Keep weeds and grass near roses under control because these are the breeding sites for grasshoppers. Insecticidal sprays with acephate, bifenthrin, cyfluthrin, lambda cyhalothrin, malathion, permethrin or pyrethrin will control grasshoppers. See Table 1 for examples of brands and products.

Table 1. Insecticides for Rose Pest Control.

Pesticide Active Ingredient Examples of Brands & Products
Acephate Bonide Systemic Insect Control Concentrate
Bacillus thuringiensis (Bt) Bonide Thuricide Bt Concentrate
Garden Safe Bt Worm & Caterpillar Killer Concentrate
Monterey Bt
Natural Guard Caterpillar Killer Spray with Bt Conc.
Safer Caterpillar Killer with Bt Concentrate
Southern Ag Thuricide Bt Caterpillar Control Concentrate
Tiger Brand Worm Killer Concentrate
Bifenthrin Bifen I/T Concentrate
Ferti-lome Broad Spectrum Insecticide Concentrate
Hi-Yield Bug Blaster Bifenthrin 2.4 Concentrate
Monterey Mite & Insect Control Concentrate
Ortho Bug-B-Gon Insect Killer for Lawns & Gardens Conc.; & RTS1
Talstar P Concentrate
Up-Star Gold Insecticide Concentrate
Cyfluthrin Bayer Advanced Vegetable & Garden Insect Spray Concentrate
Bayer Advanced Rose & Flower Insect Killer RTU2.
Dinotefuran Gordon’s Zylam Liquid Systemic Insecticide (drench)
Gordon’s Zylam 20 SG Systemic Insectcide (drench)
Valent Brand Safari 2G Insecticide (2% granules)
Valent Safari 20SG Insecticide (drench)
Horticultural Oil Bonide All Seasons Spray Oil Concentrate
Ferti-lome Horticultural Oil Spray Concentrate
Monterey Horticultural Oil Concentrate
Southern Ag ParaFine Horticultural Oil
Summit Year Round Spray Oil Concentrate
Imidacloprid Bayer Advanced Garden 12 Month Tree & Shrub Insect Control Conc.
Bonide Annual Tree & Shrub Insect Control w/ Systemaxx
Ferti-lome Tree & Shrub Systemic Insect Drench
Hi-Yield Systemic Insect Spray
Martin’s Dominion Tree & Shrub
Monterey Once A Year Insect Control II
Insecticidal Soap Bonide Insecticidal Soap Concentrate
Espoma Earth-tone Insecticidal Soap Concentrate
Natural Guard Insecticidal Soap Concentrate
Safer Brand Insect Killing Soap Concentrate
Garden Safe Insecticidal Soap Insect Killer Concentrate
Lambda Cyhalothrin Spectracide Triazicide Insect Killer – Lawns & Landscapes Conc.; &RTS1
Martin’s Cyonara Lawn & Garden Concentrate
Malathion Spectracide Malathion Insect Spray Concentrate
Southern Ag Malathion 50% EC
Hi-Yield 55% Malathion Insect Spray Concentrate
Ortho Max Malathion Insect Spray Concentrate
Tiger Brand 50% Malathion Concentrate
Gordon’s Malathion 50% Spray Concentrate
Bonide Malathion Insect Control 50% Concentrate
Martin’s Malathion 50% Concentrate
Neem Oil Bonide Neem Oil Fungicide, Miticide, Insecticide Concentrate
Ferti-lome Rose, Flower & Vegetable Spray Concentrate
Garden Safe Fungicide 3 Concentrate
Monterey 70% Neem Oil Concentrate
Natural Guard Neem Concentrate
Southern Ag Triple Action Neem Oil Concentrate
Permethrin Bonide Eight Insect Control Vegetable, Fruit & Flower Concentrate
Bonide Total Pest Control Outdoor Concentrate
Hi-Yield Indoor/Outdoor Broad Use Insecticide Concentrate
Bonide Eight Yard & Garden RTS1
Tiger Brand Super 10 Concentrate
Martin’s Vegetable Plus Concentrate
Pyrethrin Bonide Garden Insect Spray Concentrate
Monterey Bug Buster-O
Monterey Pyganic Gardening
Southern Ag Natural Pyrethrin Concentrate
Spinosad Southern Ag Conserve Naturalyte Insect Control Concentrate
Bonide Colorado Potato Beetle Beater Concentrate
Bonide Captain Jack’s Dead Bug Brew Concentrate; & RTS1
Dow Conserve SC Turf Ornamental Concentrate
Ferti-lome Borer, Bagworm & Leafminer Spray Concentrate
Monterey Garden Insect Spray Concentrate
Natural Guard Landscape & Garden Insecticide RTS1
Ortho Insect Killer Tree & Shrub Concentrate
Tau-Fluvalinate Bayer Advanced 3-in-1 Insect, Disease & Mite Control Conc.; & RTU2
1 RTS = Ready to Spray (hose-end applicator)
2 RTU = Ready to Use (pre-mixed spray bottle)
Drench = Add to water and pour around base of plant

Identifying Rose Slugs And Effective Rose Slug Treatment

In this article, we will take a look at rose slugs. Rose slugs have two main members when it comes to this family of slugs, and the particular variety and damage done will typically tell which one you have. Read on to learn more.

Rose Slug Identification

The rose slugs look like caterpillars, but they are not. They are about 1/2- to 3/4-inch in length when fully grown. The European rose slug is smooth and greenish yellow in color with a brown head and also tends to be slimy like typical slugs. The other is the Bristly rose slug, which is covered with small hair-like bristles. Both are the larvae of plant feeding wasps known as sawflies.

The Bristly rose slug will typically feed on the underside of the rose leaves, leaving the translucent lacy layer of the leaf tissue that some rosarians refer to as skeletonizing of the foliage. Thus, it turns brown, and later large holes may develop with all that is left being the main vein of the leaf or leaves affected.

The European rose slug will do virtually the same thing to the leaves affected except that they like to attack the surface tissues of the leaves rather than the underside. Thus, the Bristly rose slug can be more challenging to control.

Rose Slug Control

Contact insecticides are very effective against both family members of the rose slug family. However, it is important to note which one you may be dealing with, as to be sure to get the Bristly rose slug under control one must be sure to get the insecticide spray up under the foliage.

If only a few rose slugs are seen, they may be picked off by hand and disposed of. However, if several are seen and the damage to the foliage is significant, the use of an insecticide is important to gain control before the health of the bush or bushes effected is placed at risk.

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