Another Rose Woe

July 2nd, 2012

    While most roses are blooming earlier and better than usual this spring, a relatively new rose disease is attacking some of them — apparently at random.

This kind of distorted reddish-purple growth is a possible sign of rose rosette disease.

   Rose rosette disease is popping up throughout central Pennsylvania, and it’s particularly wicked because it’s fatal, incurable and not picky about the kind of rose it attacks.

   Hampden Twp. gardener Cristina Papson had never heard of it before her friend, Melody Oligane, pointed out some suspicious leaves on one of her favorite climbers earlier this spring.

   At first, Papson thought the clusters of deformed leaves were mutations that could be pruned off.

   “The more I researched, the more I found that it’s a fatal disease,” she says. “And it’s contagious.”

   Spread by a wind-blown mite (a tiny bug), the virus that causes rose rosette disease can’t be sprayed away or otherwise controlled.

   The prevailing advice is to yank out infected roses ASAP to reduce the spread to other roses.

   Papson, a former Penn State Master Gardener, was heart-broken to have to rogue out the deep-pink ‘Blueberry Hill’ climber that had clambered its way 30 feet up a blue-needled atlas cedar in her front yard.

   “People used to stop to see it,” she says. “It was a tourist attraction, it went up so high.”

   She’s also sacrificed two other climbers and a shrub rose called ‘The Fairy.’

   But the hardest blow is digging out a light-pink climber called ‘Dr. Van Fleet’ that drapes like a valance over her back windows.

   That nearly century-old variety is a descendent of one of Papson’s great-grandmother’s roses.

   “I grew up with that rose,” says Papson. “I got cuttings of it from my brother, who still lives in the house.”

   The irony is that Papson got rid of all of her finicky hybrid-tea roses years ago in favor of these more durable old-fashioned types.

   Apparently, though, no rose is immune from rose rosette — including the heretofore bullet-proof KNOCK OUT (R) series.

   While the problem is far from epidemic, it’s been getting around.

   James Spare, president of the Greater Harrisburg Rose Society, and his wife, Marva, a consulting rosarian, have seen rose rosette in their 450-rose collection in suburban East Shore.

   “We’ve taken out two or three plants a year for the last three or four years,” says James Spare. “It’s been very random, and it’s been all different types of roses.”

   Mary Slade, a Rose Society member for 35 years, says she’s had rose rosette on two of her 150 roses in Steelton. She’s heard of an outbreak in Chambersburg as well as occasional reports from around the Harrisburg area.

   Like the Spares, Slade dug up her infected plants.

   “I’m not taking any chances,” she says.

   If anybody has cause to worry, it’s the staff at Hershey Gardens, which grows 5,500 rose bushes of every kind.

   “We’ve had (rose rosette) for about 10 years,” says Jamie Shiffer, the Gardens’ grounds manager. “We pull about 10 or 15 roses every year. The main sign is excessive distortion of the new growth. The thorns also aren’t as hard. It’s really ugly. You know it once you see it.”

   The first sign of trouble is often shoots that grow straight up. Infected plants usually put out excess branch clusters with new leaves that are small, contorted and typically reddish-purple.

   As with the Spares, Hershey Gardens’ infections have been random.

   You’d think the disease would strike all of one variety or all roses in a particular bed. But Shiffer says it’s been very sporadic.

   “It could hit any of them anywhere,” he says. “We dig out the soil, wait a year and replant.”

   An accurate diagnosis is important because rose rosette symptoms can be confused with benign mutations, weather injuries and herbicide reactions.

   Penn State Extension offices and Penn State’s Disease Clinic (plantpath.psu.edu/facilities/plant-disease-clinic) are two resources to help diagnose.

   Some gardeners have tried to prevent trouble by spraying their roses with a miticide, figuring that if they stop the mite, they stop the disease. However, that’s expensive, time-consuming and can lead to outbreaks of other pests.

   Yanking nearby wild multiflora roses is another option since multifloras — once intentionally planted but now one of Pennsylvania’s most aggressive weeds — are highly susceptible to rose rosette. They’re thought to be partly responsible for rose rosette’s spread.

   A third prevention strategy — also time-consuming and not terribly practical — is sterilizing pruning tools with bleach or Lysol. Cleaning between bush-prunings is a way to stop tool-spread virus transfers.

   Once an infected rose dies or is removed, some experts advise waiting at least two years before replanting another rose — or switching to a different plant altogether.

   That’s the approach Papson is taking.

   She’s replacing ‘Dr. Van Fleet’ with a honeysuckle vine.