Insects That Are Harmful To Your Rose Bushes
Aphidsby Bob Bauer
Popillia japonica Also sometimes known as the Chafer Beetle Rose chafer and garden chafer are two different varieties. Japanese Beetles are a shiny copper and green beetle about 1/4 to 1/2 inch long, that can eat entire flowers as well as foliage. In areas where these are abundant, they can be devastating to the look of your blooms. Japanese beetles eat large round or oblong holes in the leaves leaf edges and flowers (especially those with light colored blooms), sometimes leaving nothing but a leaf skeleton behind. They usually eat the plant from the top down. They are not going to kill the plant, but they can cause considerable damage. They are a problem for about a month to 6 weeks in the summer when they are in their adult flying form. Before that in the spring, they are 1/2 in to 1 inch long grayish white grubs living in the soil and the grass below. They feed on grass and roots at this point. When they start showing up on roses, they appear to have flown in all at once, but this is just because they all mature at about the same time. They are a much bigger problem in areas of the USA east of the Mississippi River. More information can be obtained here: The Japanese Beetle Fact Sheet . OR Control Of Japanese Beetle Adults And Grubs In Home Lawns
Treatment: You need to go out early in the morning or late in the evening when they are the least active, and shake and pick them off the blooms by hand into a bucket with soapy water in it. This will kill them. Can be controlled by introducing milky spore (Bacillus popillae), or certain other beneficial nematodes into the soil in the spring. These will kill them as grubs. Unless all of your neighbors do this too however, you will still have some level of infestation. Another good reason to attract birds to your garden. You can also try spraying with neem oil, but this is not always effective. These beetles are repelled by garlic, catnip or geraniums. One thing that you must be careful about is that the same things that kill these beetles will kill ladybugs. Using beetle traps usually just attracts your neighbors beetles over to your yard.
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Macrosiphum rosae Also called Plant Lice Aphids are very small insects about a 1/16 to 1/8 inches long, usually light to lime green, but they can also be brown, red or black. They appear seemingly out of nowhere in the spring and feed on and damage tender new growth. They puncture the soft tissues and suck out the juices. Severe infestations will cause leaves to curl up and die, and they have been known to be able to completely kill a small new plant or just leafed out bare root rose. As they feed they excrete a sticky honeydew like substance that is attractive to ants. This honeydew substance can after a period of time grow molds and fungus and make the surface appear black and discolored. Aphids sometimes have a mutually beneficial relationship with ants, and this can work to your advantage, because the ants bite off the aphids wings and once knocked off they cannot return to the but. "I've fallen and I can't get up!" is their motto. Aphids overwinter as tiny black eggs on the stem of the rose near the new leaf buds or crevices. The young hatch on the bush and are right there where the new growth will be. Aphids are capable of producing several generations without being fertilized. At the end of the season, males and females with wings appear, mate and that is when the eggs are deposited. For more about aphids check out: Aphids on Trees and Shrubs.
Treatment: A hard spray of water from the hose can help to remove aphid infestations. Aphids reproduce very rapidly and water treatment may need to be repeated every couple days for a couple weeks. But, insect predation is the best control of aphids. It is good to keep a healthy bug ecosystem in your garden in order to promote the health of ladybugs and other aphid eating insects such as lacewings and syrphid fly larvae. It is the juvenile ladybug larvae that are the most voracious eaters of aphids. If you are a regular sprayer of pesticides you will have to buy your ladybugs at the garden store. Release them in the evening so they don't immediately go over to your neighbor's yard. It might take two weeks for the cycle of new ladybugs producing new larvae for this to take effect.
'Gertrude Jekyll'
Also called Grass Thrips or Oat Bugs. Anaphothrips obscurus or Frankliniella tritici Thrips are tiny, quick moving, sucking insects (about 1 mm long). They are dark brown in color with fringed wing tips that do severe cosmetic damage to roses by ruining the blooms. The nymphs are the same size and shape, but do not have wings and are lighter yellow brown in color. They have a life cycle of about two weeks. Thrips seem to have a preference for buds that are on the verge of opening. They will either prevent blooms from opening, or if the blooms do partially open they will be distorted and have brownish, yellowish, white or black lines and spots. The edges of the petals will turn brown. Leaves curl and leaf margins turn white yellow or brown. Damage is caused when they attack the plant tissure and suck out the sap. Severe thrip attacks will lead to buds being destroyed in place. Thrips seem to prefer light-colored flowers. They are especially active from late spring through mid summer. Thrips seem to prefer hot and dry conditions. So keeping your plants moist might help. Additional information can be found here: Grass Thrips Fact Sheet
Treatment: Cut off and remove any infected buds that you can spot as soon as you see any evidence. Then remove them from the garden totally. They don't like wet conditions and can be drowned easily, so keeping them wet is a safe treatment. They are also repelled by Alliums. Laybugs, lacewings and other beetles will eat them if you nuture these good insects in your garden. Spray the tops of the bushes with insecticidal soap, but don't spray too often, because they can become resistant to this treatment. Beneficial nematodes can be added to the soil in the spring. They will eat the thrip larvae. Chemically, thrips can be controlled by spraying the buds and blooms with Orthene, mixed with one tablespoon of dark brown sugar per gallon of water.
'Jayne Austin'
Cane borers are the larvae of Sawflies and Carpenter Bees and some Wasps. Ceratina spp. Cane Borers can enter the rose through the tops of pruned canes. These pests lay their eggs on the freshly pruned stems of roses in the late spring or early summer. The eggs hatch and the larvae bore and eat their way into the center of the plant down the length of the cane. This can kill the cane down as far as the borer goes. If the borer reaches the bud union, it can sometimes lead to the death of the rose. If you notice a small hole in the center of a pruned cane end, you probably have cane borers. Wilting, and dying foliage at the top of the bush with yellowing leaves which drop off can also indicate the presence of cane borers. Sometimes you will notice a small swelling where the cane borer is present inside of the cane. As the borer hollows out the inside of the rose cane (the pith), the cane will turn brown lose all its foliage and die. You can learn more about carpenter bees from the Carpenter Bee Fact Sheet
Treatment: Prune the bush below any areas of pith damage. Put a little dab of household glue, tree wound paint, wax or nail polish on any pruning cuts that are over the diameter of a pencil. Add a dropof food coloring to the glue so that you can tell which canes you have dabbed. These insects are somewhat repelled by plantings of Alliums.
Indications: Leaves discolor, wilt and drop off. Growth can be stunted. These tiny insects attach themselves permanently to a rose cane they hide underneath small gray or brown oval shells. They sometimes can appear to look like a bed of little oysters. Scale insects insert sucking tubes and draw out plant juices to feed on them. If left to their own devices, they are capable of rapid multiplication and serious damage to the plant. Scale bugs are relatives of mealy bugs, whiteflies and aphids.
Treatment: The good news is that they can easily be rubbed of with a rag or squirted off with blasts of water from a hose. They are also the food source for lacewings.
These are slender yellowish or greenish insects feed on the underside of the leaves causing pale, mottled or flecked marks on the surface of the leaves. The adults are winged and when disturbed take flying leaps. Where extensive damage occurs there may be premature leaf-fall. These small insects are often seen on the underside of the leaves. Leaf Hoppers are a bug that sucks the plant juices. The feeding causes curling, stunting and dwarfing accompanied by a yellowing, browning or blighting of the foliage know as hopperburn or tipburn because the damage is first seen at the leaf tips working inwards.
The leaf hopper is small (3mm), pale green and wedge shaped. They are very fast and often not seen by the gardener until the damage is so great that you finally look carefully. It sometimes is too late then. If leaf hoppers are in your area, look now and continue looking on a regular basis. The best way to spot them is to run your hand over the top of the crop lightly brushing the leaves. If you have them you will see them hop quickly. If you have them bad you may see a cloud of them jump away.
Whitish spots or stippling on upper leaf surface are evidence of rose leafhopper feeding. Sticky honeydew secretions from leafhopper feeding frequently cover lower plant part are called "tar spotting." Leafhoppers feed with piercing-sucking mouthparts. Damage is caused by nymphs and adults removing chlorophyll and sap from the lower leaf surface which can affect bud formation. They overwinter on roses floribunda roses are most vulnerable. Rose leafhopper adults are long and slender, wedge-shaped, with a convex back. The body is a light yellow with the head slightly darker. Juveniles are generally pale white, wingless and "scurry" around when disturbed. Rose leafhopper nymphs have a few small black spots on the black of the thorax and wingpads. Rose leafhopper can overwinter as eggs on wild roses and brambles. Nymphs emerge in the spring and feed on the wild hosts. In June, newly emerged adults disperse.
Treatment: There are insecticides that are specifically targeted for leafhopper. The only organic control that works for the leaf hopper is a concentrated pyrethrum spray such as Pyrenone or Pyronyl. Keep in mind that are many organic certification agencies that do not allow pyrethrum as it contains PBO.
Sawflies are a small non-stinging
type of wasp. Adult sawflies are not a problem, but the larvae are. Sawfly larvae are also called Roseslugs. They feed from May to September for 2-3 weeks when they are in larval stage, and then they change into adult flies and the feeding stops. The reason they are called roseslugs because of their slug-like appearance. The larvae also resemble caterpillars, but they are not true caterpillars.
There are several types of sawflies that attack roses as larvae.
The bristly roseslug is a major pest on roses. The larvae are pale green, with a brownish-orange head and very small, bristlelike hairs. They skeletonize the leaf from the underside when small, and then chew holes through the leaf as they enlarge.
The curled rose sawfly occurs in lesser numbers, but each one can cause relatively substantial damage. The curled rose sawfly larvae skeletonize leaves when small and eat the whole leaf, except the main vein, when large. To make matters worse, when they pupate they bore into the pith of twigs, killing portions of the twig and opening it up for fungal infections. The larva has a yellowish head with black eye spots, and a pastel green body with white dots down the length of it.
The roseslug is the third type of sawfly to occur on roses. It looks somewhat similar to the bristly roseslug, but lacks the hairs. It skeletonizes the upper surface of a leaf.
Treatment: If there are only a few rose bushes infested with the roseslugs, you can mechanically pull the leaves off and kill any larvae found on the upper or lower surfaces of the infested leaves. If the damage is widespread across many rose bushes in your garden and a lot of damage is being sustained, chemical control should be considered. Just about any contact insecticide labeled for use on roses will kill the roseslugs. Try to use the least toxic one possible, because you don't want to kill beneficial insects in your garden.
Also known as Rose Maggots. Midge damage is very diagnostic. The tiny rose midge larvae feed on the tender new growth and immature buds. When they have eaten, the buds and new growth turns black and withers. Adult rose midges are mosquito-like in shape and appearance. They are about 1-2 mm in length. The females lay their eggs inside the sepals of flower buds or leafy tips. The larvae then hatch from the eggs and damage the buds and rose tips. The full-grown larvae may measure up to 1.8 mm long and are sometimes reddish in color. The pupae stage usually occurs in the soil but pupae have also been observed in the damaged rose tips. When they leave the damaged tip, the buds wither, blacken, and die. The adults emerge from pupae in the soil early in the spring at the same time as the production of new rose plant growth and flower buds. There are several overlapping generations per year and a single generation, or life cycle, can be as short as two weeks. Populations of the midge build up until early fall and the last generation overwinters in the ground in cocoons.
Treatment: Insecticidal soaps. These specially formulated soaps are a key element in any least toxic pest-control strategy. They are effective against a wide range of mite and insect pests. Soaps are essentially nontoxic to humans and wildlife, but they can damage some plants, especially ones with dull leaf surfaces or many leaf hairs. The best time to apply insecticidal soaps is early morning or late afternoon Rose midges do not occur in all areas of the world, but some home gardeners who have a very serious problem will need to practice a preventive control program consisting of repeated soil treatments and foliar insecticidal sprays. Successful control measures require repeated soil and foliar insecticidal applications. Repeated applications of Diazinon to infested soil as well as a foliar spray give excellent control. Spraying the infested soil around the roses with Diazinon and treating the foliage with Mavrik at a 10-day treatment schedule, is also a recommended treatment.
Also known as Frog Hoppers, Spittle bugs are easy to spot because of the foamy looking "spit" nests that they make on the stems of your roses. They rarely do severe damage. There are more than 23,000 species of spittlebugs worldwide and they tend to be somewhat host-specific like their brethren, the aphid. The species in your gardem is most likely the Meadow Spittlebug (Philaenus spumarius). Female spittlebugs lay eggs on or near host plants in the summer. The eggs overwinter and hatch in the spring. As the nymphs ingest plant fluids, their exudate is voided to create the "spittle." The nymphs surround themselves with this gooey mess presumably to maintain a humid environment in which to develop.
Treatment: You can knock them off with a hard spray from the garden hose, or wipe them off the stem with a rag. They are preyed upon by yellow jackets. Insecticidal soap sprays or horticultural oil solutions work, but must penetrate the spit bubbles to be effective. Most gardeners simply wait out the nymphs for a few weeks, and the plants recover quickly.
Treatment: Many species of weevils are resistant to many insecticides, since these pests are regularly seen in commercial farming. The best thing to do is to hand pick the adult weevils off of the blooms as soon as you see them, then remove the damaged buds and spent blossoms. This will prevent continuing damage minimize the chance of large populations the following year. Make sure that you look for them in other places in the garden too, no just the roses. Adult weevils drop readily from plants and feign death when disturbed. In order to take advantage of this behavior, collect the adult weevils with a wide mouth container half full of soapy water. Touch the plant parts where the weevils are feeding and they readily fall down into the soapy water and drown.
Several species of wasp-like insects lay their eggs in stems of roses and their larvae cause large swellings or galls. One species makes a gall resembling fibrous moss on the stem. Another causes a large wart-like gall near the ground surface. These galls may be confused with the crown galls caused by bacteria. However, if insect galls are cut open, numerous larvae, or the cells in which they develop, will be visible. No known insecticide will control the insects that produce these galls.
Treatment: The best available control is to prune the infested stems to remove the galls and bury them promptly to destroy the larvae in the galls before they emerge. Cut off and throw away any galls that are seen on your rosebushes. Cut them well below the infestation.
Leaf cutter bees cut semi-circle shaped holes in the leaves of roses. The damage looks worse than it really is. Usually, there are a limited number of these bees in your garden and the damage they will do is only cosmetic. They pose no real threat to rose health, but they drive rose exhibitors crazy. A couple of bites out of the leaf on that otherwise perfect boom can be disappointing.
Treatment: My advice is to just leave them alone. Their damage is usually minor. If you are a serious rose exhibitor, you are probably spraying like crazy anyway and they won't be living in your yard.