Stumped by something in your garden? Ask the Extension Agent!
Kirsten Conrad is here to help. She’s the Virginia Cooperative Extension Agent, Agriculture and Natural Resources – Horticulture, for Arlington County and Alexandria. Submit your question with photos to the Extension Master Gardener Help desk at mgarlalex@mgvn.org, and she may pick yours for this occasional feature. Please include your phone number in case she has questions.
Question:
Dear Kirsten,
Our friend, a Master Gardener, was helping us in our garden, and she noticed scale on our Japanese plum prostrate yews. She suggested we ask you what kind of scale this is and what can be done to get rid of it. See the photos below. Thanks so much for any information you can provide.
Answer:
Hello gardener,
GREAT photos. Thanks for sharing. This is probably Cottony Camellia Scale.
You have multiple tools for dealing with these peculiar insects that feed on plant sap.
- First, you can apply a horticultural oil spray during the plant’s dormant season to smother overwintering eggs and adults.As this is an evergreen, I would take great care to ensure that the label specifically lists use on your type of evergreen. In some cases, the oil sprays can remove the ‘bloom’ from evergreen foliage and dull the color.
- Two chemical treatments are listed for homeowner use: dimethoate and imidacloprid. The optimal time of treatment is when crawlers are active: May 1 to June 5 and Sept. 15 to 30. Specifically, treatment should be commenced May 10 to 20 and/or Sept. 10 to 20.
- For imidacloprid, see “Bee Advisory Box” as this systemic insecticide can affect any insect feeding on any plant part. While bees are not a huge visitor to this plant, care and consideration of bees should still be taken.
- Biological controls include the encouragement of natural predators — ladybird beetles or parasitic wasps.
- Cultural controls would include scraping off and disposing of these white egg masses and/or the removal of leaves, if the infestation is limited.
Here’s a related fact sheet from Virginia Cooperative Extension: Scale Insects.
Happy Gardening,
Kirsten
Question:
Dear Kirsten,
Photo © 2016 Christa Watters
Citrus is both an evergreen plant and one that can bloom pretty much any time of the year if the ambient temperature dips into the 60s at night. In my experience here in Baltimore, that means it usually sets blossoms indoors in January or early February and then again sometime in June, after I have put it outside.
What time of year would be most beneficial to prune citrus plants?
Answer:
Citrus can be pruned anytime, but the best time in our climate is right after harvest or in early spring up to March. Your goal is to remove branches that are poorly placed, suckers, and anything that looks unhealthy without removing more than a third of the healthy leaves. My suggestion is that you prune to shape the tree immediately before the blossoms open, twice in the year as needed. Some blossoms will be lost, but yield will not be affected.
Happy gardening,
Kirsten