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Information, including identification, symptoms and control, related to most common pests that plague rose growers in Western Missouri and Eastern Kansas. 
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Insects that chew and suck can be especially harmful to roses. Not only do they disfigure and weaken the plant, they can also spread disease pathogens.

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Select Below to Learn More About

• Aphids
• Cane Borers
• Japanese Beetles
  
• Leef Cutter Bees

• Midge
• Rose Slug
• Spider Mites
• Thrips​

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Aphids  
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Description:

• Small green or black insects, with or without wings, about 1/8 inch long.
• Appear throughout the spring and fall.
• Suck the plant juices from tender parts of the plant, such as, new foliage and buds.
• Excrete honeydew, a sweet sticky substance that attracts ants and favors the growth of sooty mold.
• Prolific breeders and multiply rapidly in warm weather.

Symptoms

• Leaves curl upward.
• Buds are deformed.
• Buds may fall before opening.
  
  

Control

• Easily controlled, washing the plant with a stream of water will knock the aphids off the plant, and since most cannot fly, they will not be able to return to the plant. 
• Most insecticides will control aphids.
• Natural enemies that feed on aphids such as lady beetles, lacewing larvae and parasitic aphid wasps.

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Reference: K-State Extension, Common Pest Problems PDF

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Cane Borers

Description:

• Several wasps and bees lay eggs in the pith of cut rose canes.
• Larvae bore a hole down the middle of the pith to make their nests.
• Active boring from spring through early fall.

Symptoms

• Damage is easily seen, a hole in the center of a cut cane.
• Hole may only be a few inches deep or down to the base of the plant.

Control

• The most common cane borer wasps are predators, so keeping aphids under control will ​remove their food source.
• Damaged canes should be cut below the larvae to prevent generation of cane borer wasps.
• Borer damage can be prevented by sealing each cut cane after pruning with waterproof wood glue.

           
Reference: Plant Talk, Colo. State, Rose Cane Borer  PDF

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Japanese Beetles
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Description:

•  3/8 inch long metallic green beetle with copper-brown wing covers.
• Adults emerge in June and feed on plants.

Symptoms:

• Feed individually or in large groups.
• Totally consumed flowers and flower buds.
• Skeletonized leaves starting from the top of the plant.

 
Control:

• Can be removed by hand and placed in a container of soapy water.
• Many insecticide are available for control.
• Don’t use Japanese beetle traps because they attract more beetles from the surrounding area.

 
References:

• Entomology CA, UKY  PDF​
• Extension UMN, Japanese Beetles  PDF​

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Leaf Cutter Bees

Description:

• Rarely seen and are similar to honeybees.
• Excellent pollinators of alfalfa and other crops.

Symptoms

• Perfectly cut semi-circles on leaf edges.
• Little other damage. 
• Mostly an aesthetic problem.
• Often prefer the leaves of a particular rose.

Control

• Control by insecticides is questionable due to their value as pollinators.

Reference: Missouri Botanical Garden, Leaf Cutter Bees  

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Midge
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Description:

• A tiny fly lays its eggs in the flower buds and new shoots.
• Fly larva’s rasping mouth parts cause damage to the soft rose tissue.

Symptoms:

• Bent and misshapen flower buds and withering shoots.
• Black flower buds and shoots.
• Flower buds and shoot tips fall off.
• Lack of flowers.

Control:

• Prune out affected buds and shoots.
• Treat soil with imidacloprid drench or granules
• Spray plants with lambda-cyhalothrin or other pesticide listed for midge.

References:

• U of Minn., Rose Pests
• Ohio State U., Rose Midge

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Rose Slug
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​Description:

• Caused by the yellow-green larval stage of several different sawflies.
• Feed on the soft tissue of rose leaves.

Symptoms:

• Soft tissue of leaves is missing, while tough veins are left intact.
• Papery, translucent leaf surface which crumbles to leave holes.
• Holes appear as tissue crumbles.

Control:

• Remove affected leaves at first sign of damage
• Use a forceful spray of water on both sides of the leaves to knock-off larvae. 
• Minimize use of pesticides to allow beneficial predators to control.
• Many organic and chemical controls are available for control if needed. 

References: 

• Missouri Extension, Rose Slug PDF
• Oregon State, Rose Slug 

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Two-spotted Spider Mites
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Description:

• Tiny mite with two red spots.
• Mouth-parts adapted to suck the juices from plant tissue, especially leaves.
• Feed on most landscape plants as summer temperatures heat up.  

Symptoms:

• Leaves become spotted or stippled, dull, and lose substance, then become yellow or bronze, and then fall off.
• Telltale webbing on the underside of the leaves.  
• Major infestations can lead to death of parts of the bush or the entire bush.  
• Presence of spider mites can be confirmed by shaking a branch of the plant over a white sheet of paper.  Tiny, dark specks will be seen moving across the paper and will leave a red streak if squashed with a fingertip.

Control:

• Controlled at first sign of spider mite activity by spraying the underside of the affected leaves with a forceful spray of water every three days.  
• Organic controls include insecticidal soap and horticultural oils.  
• Spider mites are not insects, but are related to spiders, so many insecticides are not effective for control.
• Pesticide must be labelled for mite control.  

Reference: K-State Extension, Spider Mites  PDF

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Thrips
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Description:  

• Tiny, slender brownish yellow winged insects.
• Just visible with the naked eye hiding at the base of the flowers.
• Hide inside buds and blooms and damage the petals with their rasping mouth-parts.
• Prefer lighter colored blooms and attack the bloom when it is still a bud making control difficult as they hide inside an unopened bloom.

Symptoms:

• Browning and brown streak of the flower petals.
• Flowers deformed and petals drop quickly.

Control: 

• The link below has a long list of possible control options.
• Because thrips lay their eggs in grasses and weeds, keep the garden weed-free and control grasses.

Reference: U of California, Pest Notes