Knock Out Rose Rosette Disease: Controlling Witches Broom Disease

While it’s a myth that everyone loves roses, they remain one of the most popular and expressive flowers a plant lover can grow.

In recent years, a new type of landscape roses has taken the world by storm for its beauty and very un-roselike ease of cultivation.

Knock-Out Roses remain vulnerable to rose rosette diseasePin
Rosette Rose disease

Known as Knock Out Roses, this growing family is very forgiving and can even tolerate a little neglect.

Unfortunately, sometimes a rose is just a rose, and Knock-Out Roses remain vulnerable to the infamous rose rosette disease.

Originally considered a beneficial control method when wild multiflora roses became invasive, the rose rosette is a deadly disease spread by tiny eriophyid mites that also attack Aloe plants.

Dealing with this infection early on is vital, as infected plants will quickly become incurable.

Rose Rosette Disease On Knockout Roses

Sometimes referred to as witches broom, rose rosette is a growing problem for rose growers and can easily spread.

Understanding this disease and how to treat it can potentially save your Knockout Rose collection (and regular roses) from an untimely demise.

What Is Rose Rosette?

Rose rosette is caused by a virus most commonly spread through eriophyid mites (AKA wooky mites) which feed on rosebushes.

These mites are small enough that they’re often spread on the wind, making detection and control difficult.

Once infected, a new plant will begin rapidly, creating new, deformed shoots of an unusually bright red.

Unlike normal growth, an infected cane will retain its red color, and new leaves will fail to unfurl, giving the impression of little rosettes.

Any rosebuds which form on the plant will either be deformed or fail to blossom.

As more infected shoots grow, the healthy portions of the bush will die back until the entire plant is killed.

There’s no cure for rose rosette, but there are ways to treat infected roses if caught soon enough.

Providing Immediate Treatment

The moment you first notice traces of rose rosette, it’s imperative you treat the plant.

Don’t put it off because the virus can spread through your plant’s veins while you wait.

Target each infected shoot and cut them off a few inches below where the healthy green tissue ends.

This is not a cure, and you will need to carefully monitor the plant to make sure new signs of infection don’t appear.

However, if caught quickly enough, it’s possible you’ll remove the virus before it has a chance to spread.

NOTE: Neem soil drenches and other common antifungal methods known to target some bacteria will have no effect on this virus.

More on: Knockout Rose Diseases

The Best Prevention For Rose Rosette Control on Knock Outs

Pruning is very much like a haircut for roses.

It allows you to trim away scraggly or damaged bits so it will grow back fuller and healthier.

While Knockout Roses can be perfectly healthy without an occasional trim, this bit of extra grooming can be an important prevention technique.

The nursery responsible for first distributing Knockouts, Star Roses and Plants/Conard-Pyle, suggests you should prune back rose bushes in late winter by ⅔.

Check out our article on Pruning and When To Cut Back Knockout Roses

Not only will this encourage newer, healthier growth, but it can get rid of most or all pests that have decided to overwinter on your plants.

This includes the mites responsible for the spread of rose rosette, scale, and many other little nasties.

It can also help combat other diseases Knockouts face, such as black spot disease.

The Final Solution

Unfortunately, the rose rosette is highly virulent – and not just because it’s a literal virus.

Growers who don’t catch it in time or may have other roses nearby only have one possible solution – eradicating the bush itself.

Carefully dig up the rosebush, being sure to get the entire root system. Place the bush in a sealable plastic bag and dispose of it immediately.

The soil may contain mites or traces of the virus, so it is generally recommended you avoid planting any new roses on the spot for two full years after extracting a plant with rose rosette.

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