Signs of Common Rose Pests
As spring unfurls, plants aren’t the only things waking up outdoors. Insects are also coming to life. Spring pests that survived winter are hatching, and insects that burrowed into soil or beneath leaf litter to ride out the cold are emerging. After a long winter’s nap, these pests are ready for a good meal.
Some pests specifically target roses. You can help protect plants by inspecting them a few times a week. Pests reproduce quickly, though, so you want to be sure you recognize the symptoms of a problem before it becomes a major headache. Use our guide to sharpen your pest-spotting skills.
These sucking insects show up early in the season, before the first rose ever opens. Oval-shaped, small and light green or pinkish, aphids are easy to overlook. They reproduce rapidly, which is why one day your roses look fine, and the next day stems appear alive with movement.
Aphids suck the juices out of new shoots, buds and leaves. They produce honeydew, a sweet, sticky substance that hosts black sooty mold and attracts ants. If you miss the bugs clustering along new growth, you may see black mold or possibly ants racing up and down stems.
Other signs of aphids: curled, stunted or puckered leaves; yellowing leaves that fall from stems; misshapen blooms with streaked petals
Two kinds of inchworms affect roses: the fall inchworm and the spring inchworm. They’re actually cankerworm caterpillars. Both types hatch in spring when air temperatures hit the 50-degree mark.
You’ll typically spot them on unopened rose blooms, inching along petals, munching as they go. Infested roses are usually located beneath trees. The worms drop from the trees to the roses.
Other signs of inchworms: misshapen blooms with streaking on petals; edges of unopened buds are rough and nibbled
Several types of sawflies attack roses. These pests look like caterpillars but aren’t – and they’re not slugs, either. That means you can’t treat them using traditional caterpillar or slug controls. They’re about 1/2 inch long and move like an inchworm.
Sawfly larvae frequently feed along leaf undersides, sucking out the green parts and leaving a transparent, papery spot. Larvae feed for about four weeks before pupating. If you spot damage early and identify the culprit, you can treat. Depending on which sawfly species is present, you’re facing one to six generations per year.
Signs of rose slug sawfly: holes or papery spots appear along leaf midribs, then move toward leaf edges; skeletonized leaves
Cottony Cushion Scale
Scale insects lay eggs on rose stems in fall. Eggs hatch in late spring, and the young scale insects prowl along rose stems, seeking a spot to latch on and start sucking. The surest sign of scale is white, circular, limpet-looking things on rose stems. In early spring, egg cases are visible as white cottony masses.
Scale feeding produces honeydew, which attracts ants and may grow black sooty mold. Plant surfaces become sticky in a severe infestation.
Signs of scale: stems encrusted with small white circles; sticky plant surfaces; ants crawling up and down stems; black sooty mold growing along stems
When thrips are present, you get brown, streaky buds that only partially unfurl. Thrips are tiny (1/16 inch long), slender sucking insects that are usually yellow, brown or black. They’re very difficult to see. Normally you have to shake a bud over a piece of white paper to spot the insects.
Thrips typically infest roses when conditions are hot and dry. If an unseasonal spring heat wave arrives, watch for thrips. Otherwise, they usually appear as summer arrives. They prefer light-colored blooms in shades such as pale yellow, white or light pink.
Signs of thrips: flower buds don’t open; petals have brown streaks; petal edges look ragged and brown; infested flowers that open are distorted
You’ll also see beneficial insects in spring, including ladybugs, green lacewings, spiders and praying mantises. Don’t disturb or discourage these critters. They’re your partners in controlling pest outbreaks – not just on roses, but in your garden.
Image UGA5082075: Whitney Cranshaw, Colorado State University, Bugwood.org
Image 5439081: Joseph Berger, Bugwood.org
Image 5429886: Brian Kunkel, University of Delaware, Bugwood.org
Image UGA1482004: Sturgis McKeever, Georgia Southern University, Bugwood.org
Image 1476101: Whitney Cranshaw, Colorado State University, Bugwood.org