A close-up shot of Leslie’s once-again healthy camellia shrub.

Duchess of Dirt: Dormant oil cures ailing camellia

Leslie Cox

Special to The Record

Good news! Well, mostly good news.

I checked our 50-year-old camellia shrub over recently. Last winter, it was looking quite sickly. There were a number of yellowing leaves, covering almost half of the shrub, and many of those were covered in a black, sticky, soot-like substance. Flipping those yellowed leaves over, I discovered quite a number of rectangular-shaped, white, fluffy objects.

Turns out, our camellia shrub had been infected by cottony camellia scale (or Pulvinaria floccifera, to be botanically correct). And what I was seeing on the underside of the leaves last winter were the empty egg sacs from the previous generation.

Doing some research into this pest, I discovered other afflicted gardeners were using dormant oil spray to control this pest. I also found a reference on the UBC Botanical Gardens forum claiming they were undertaking this same treatment to control the outbreak they had on their camellia shrubs.

So we followed suit. John valiantly gave our shrub a dousing of dormant oil on the underside of the leaves. Not an easy task considering the shrub stands taller than him, the leaves reach all the way to the ground, and the shrub itself is wedged up against the house.

The good news? The leaves on our camellia shrub have returned to a healthy green colour this year and the black soot substance has disappeared.

That black soot, by the way, was actually a fungal mould which often develops as a residual from the honeydew the scales excrete as they suck the sap from the leaves. Always a clear indication there is something wrong with your plant which needs immediate investigation.

Doing an inspection on the underside of the leaves this year, I only found a total of five ovisacs in a random search of about 50 leaves. Searching further, there were very few ovisacs anywhere. One more spray treatment this year should get the remaining overwintering scales and then we will leave the camellia alone.

Word of caution about dormant oil and lime sulphur sprays: annual applications are not recommended as these products kill beneficial insects, along with the pests. So only spray your trees and shrubs when you actually have a pest problem, as we did with our camellia.

Having said that, horticultural oils are actually a safe and effective method of controlling certain pests such as aphids, mites, and scales.

Once upon a time, their use was restricted during winter months when plants are dormant because of their possible toxic threat of causing real injury to the plant itself.

However, improvements in petroleum oil refining, its base ingredient, has now made these oils safe to use as pest treatments after leaf bud break, in the summer months, and on leaves of evergreen plants such as the camellia.

But there are still restrictions on usage, even with their improved safety. These include:

• Do not apply when shoots are growing

• Avoid applying when temperatures are excessively low (below freezing), or high (above 38 deg C)

• Do not apply if plant tissues are wet or rain is imminent

• Do not apply in fall until winter hardening has occurred

•Do not use in combination with sulphur-containing pesticides

To find out more about horticultural oils, check out my website: www.duchessofdirt.ca.


Just Posted

A Tribe Called Red, Tanya Tagaq among artists featured in Indigenous music film

When They Awake coming to Stan Hagen Theatre for one night

CVRD moves to goal-setting stage for sewer service plan

Workshops planned for next week in Comox and Courtenay

Comox Valley Santa’s Workshop in need of bicycles for youngsters, gifts for teens

Santa’s Workshop, at 464 Puntledge Road (formerly the Red Cross building), is… Continue reading

Comox connection to launch of new $10 bill

Great nephew of Viola Desmond says bill is a ‘step in the right direction’

Changes coming to BC Ferries reservations for Vancouver Island routes

Many customers are booking multiple reservations, inflating wait times

Police aim to prevent retaliation after Hells Angel found dead under B.C. bridge

IHIT confirms Chad Wilson, 43, was the victim of a ‘targeted’ homicide

Mid Island Farmers Institute discusses fleece at November meeting

Are you a lover of wool and local fibre? Interested in raising… Continue reading

Comox Valley Nature invites the public to learn about nature photography

Comox Valley Nature is hosting a public lecture on photography. Join Terry… Continue reading

The latest advent calendar trend: Holiday cannabis

A Canadian company is giving people from coast to coast a new way to celebrate the Christmas countdown.

B.C. woman allegedly threatens to rip out intestines of American man

A Kamloops-area woman is accused of harassing and threatening to disembowel an American man

B.C. model looks a lot like expanded taxi industry, ride-hailing group says

Ridesharing Now for BC says it had hoped the bill would be more customer-driven like in other cities

Otter makes a snack out of koi fish in Vancouver Chinese garden

Staff say the otter has eaten at least five fish

731,000 Canadians going into debt to buy prescription drugs: UBC

Millennials and those without private coverage were more likely to borrow money

Pot users, investors need to be vigilant at Canada-U.S. border

U.S. authorities say anyone who admits to having used pot before it became legal could be barred

Most Read