4 Common Rose Pests
and how to prevent them...
1) Aphids
Description: Tiny sucking insects that feed on plant sap. Often
found clustered on young plant growth, especially on over-
fertilized plants.
Symptoms: Leaves may turn black with sooty mold.
Prevention and Control: Spray with a strong stream of water
early in day, or rub off small quantities. Insecticidal soap may
help. Avoid high-nitrogen fertilizers to avoid too rapid growth
spurts. Encourage natural predators like parasitic wasps and
lady beetles. Ants sometimes feed on honeydew excreted by
aphids, and may prevent beneficial insects from eating aphids.
Control ants with environmentally-friendly baits and sticky
barriers on roses.
2) Thrips
Description: Small, thin yellow-brown or black insects that attack
rose flowers, both as winged adults and larvae.
Symptoms: Cause damaged or deformed petals with brown
edges. Thrips often favor fragrant, light-colored or white roses.
Prevention and Control: Thrip problems are highest with many
rose bushes planted alone together. Encourage plant diversity in
your rose garden. Plant roses away from weedy areas. Remove
spent blossoms promptly.
Most thrips are difficult to control effectively with insecticides,
because the pests are protected by plant parts. Neem oil,
insecticidal soap or narrow-range oil may provide relief if applied
early. They are less toxic to beneficial insects. Some natural
predators, such as minute pirate bugs and predaceous mites,
help control certain thrip species. A strong spray or water will
knock thrips off plants.
3) Leafcutter Bees
Description: Small bees that use leaf material to line their nests.
Symptoms: These bees cut semicircular holes in leaves. Other
than aesthetic problems, these bees cause no serious damage to
plants.
Prevention and Control: Leafcutter bees are important crop
pollinators, especially of alfalfa. There aren’t any effective
controls, so it’s best to remove damaged leaves and tolerate a
little damage.
4) Spider Mites
Description: Tiny mites that bruise plant cells with their
mouthparts and suck the sap.
Symptoms: Leaves are stippled or yellow, often with webbing.
Leaves may dry up and fall.
Prevention and Control: Spider mites are most prevalent in hot,
dry conditions, and when natural enemies have been killed by
insecticides. Provide roses with sufficient irrigation, and
periodically wash leaves with water in early hours. If severe, try
insecticidal soap, neem oil or horticultural oil.
and how to prevent them...
1) Aphids
Description: Tiny sucking insects that feed on plant sap. Often
found clustered on young plant growth, especially on over-
fertilized plants.
Symptoms: Leaves may turn black with sooty mold.
Prevention and Control: Spray with a strong stream of water
early in day, or rub off small quantities. Insecticidal soap may
help. Avoid high-nitrogen fertilizers to avoid too rapid growth
spurts. Encourage natural predators like parasitic wasps and
lady beetles. Ants sometimes feed on honeydew excreted by
aphids, and may prevent beneficial insects from eating aphids.
Control ants with environmentally-friendly baits and sticky
barriers on roses.
2) Thrips
Description: Small, thin yellow-brown or black insects that attack
rose flowers, both as winged adults and larvae.
Symptoms: Cause damaged or deformed petals with brown
edges. Thrips often favor fragrant, light-colored or white roses.
Prevention and Control: Thrip problems are highest with many
rose bushes planted alone together. Encourage plant diversity in
your rose garden. Plant roses away from weedy areas. Remove
spent blossoms promptly.
Most thrips are difficult to control effectively with insecticides,
because the pests are protected by plant parts. Neem oil,
insecticidal soap or narrow-range oil may provide relief if applied
early. They are less toxic to beneficial insects. Some natural
predators, such as minute pirate bugs and predaceous mites,
help control certain thrip species. A strong spray or water will
knock thrips off plants.
3) Leafcutter Bees
Description: Small bees that use leaf material to line their nests.
Symptoms: These bees cut semicircular holes in leaves. Other
than aesthetic problems, these bees cause no serious damage to
plants.
Prevention and Control: Leafcutter bees are important crop
pollinators, especially of alfalfa. There aren’t any effective
controls, so it’s best to remove damaged leaves and tolerate a
little damage.
4) Spider Mites
Description: Tiny mites that bruise plant cells with their
mouthparts and suck the sap.
Symptoms: Leaves are stippled or yellow, often with webbing.
Leaves may dry up and fall.
Prevention and Control: Spider mites are most prevalent in hot,
dry conditions, and when natural enemies have been killed by
insecticides. Provide roses with sufficient irrigation, and
periodically wash leaves with water in early hours. If severe, try
insecticidal soap, neem oil or horticultural oil.
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| Published in Gardening How-To Magazine March/April 2006 |
