Many of our Riverhouse rhododendrons and azaleas are failing due to an infestation of lace bug.
Azaleas, rhododendrons face severe threat from lace bugs
Lace bugs usually become active in mid- to late May and early June, when they start laying eggs, but could get going earlier this year because of the mild winter. The bug is especially persistent because several generations are produced in one year, each one as hungry as the last.”
“Start looking now for eggs, which look like brown spots along the veins on the underside of evergreen azalea and rhododendron leaves. Once adults appear, you’ll see yellow dots on the surface and black feces on the underside. Eventually, foliage turns white, which is a sign the plant is not long for this world.”
Howard Donnelly of NW Trees says he has used Safari on Azaleas and Rhodies for 2 years without any harm to pollinators.
“With my applications, I use a soil drench method to insecticide off any blooming plants so it does not come in contact with pollinators.”
Jane volunteered to do some research on Safari for us and uncovered the information below.
Insecticide temporarily banned by Oregon Department of Agriculture after 50,000 bumblebees die in Wilsonville
Learn more >>
“To summarize, the disclosed toxin in Safari is Dinotefuran. It is a neonicontinoid which is the insecticide which caused a couple of big bee die-offs in Oregon last year and is now banned in Portland. I was told that this was the insecticide our landscape company wants to use to treat the Rhododendrons.”
Thank you, Jane, for researching this.
The Landscape Committee voted “no” to spraying Safari to control the lace bug.
However, many diseased plants have been marked with flags for removal.
In an attempt to look for other options to save our beloved rhododendrons and azaleas, John and I made a trip to the Crystal Springs Rhododendron Garden in Portland yesterday. It was a gorgeous northwest day to meander through those magical trails!
Dennis O’Malley, of the Portland Chapter of the American Rhododendron Society, was generous in sharing his anecdotal lace bug experience with us, explaining that The Crystal Springs Rhododendron Garden falls under environmental codes of the City of Portland banning many pesticides. So they had been experimenting with other solutions for dealing with the region-wide infestation of the lace bug.
The lacewing is a natural predator of the lace bug (confusing I know).
Lacewings are beautiful little green or brown insects with large lacy wings. Individual white eggs are found laid on the ends of inch-long stiff threads. It is the larvae that destroy most of the pests. They are sometimes called aphid lions for their habit of dining on aphids. They also feed on mites, other small insects and insect eggs.
Soap & Oil Sprays
The important point to remember is that the lace bugs attach to the underside of the leaves and the spray must come in direct contact with the bug to be effective. Dennis recommended the Safer brand of Insect Killing Soap. He also suggested a 1 gallon Gilmour Sprayer with a wand to help get up underneath the leaves. This has to be repeated every couple of weeks because the spray does not effect the eggs and new eggs hatch about every 14 days. He also talked about Kelp Spray which is believed to be released systemically providing extended protection.
Dennis said that he didn’t believe that removing one infected plant will have any effect on keeping others from becoming infected because it is an air-born region-wide infestation. He also said that he didn’t believe the lace bugs would kill a healthy plant. It may look a bit scraggly for a couple of years, but if you nourish it and bath it regularly in soap spray, it should pull through. That is obviously not an option on a large scale commercial level, however individual property owners may want to invest some time in nurturing a shrub they particularly love.
Another Rhododendron Society member shared her personal recipe for an organic systemic spray as we signed up for Membership. She recommended:
1 TBSP Kelp
1 TBSP Iron
1 TBSP Magnesium
1 GAL Water
Thank you Portland Rhododendron Society for so generously sharing your time, experience, and love of these northwest treasures!
I found a Safer Insect Killing Soap with Seaweed Extract that I am going to try on the rhododendrons and azalea by unit 444 that showed signs of lace bug last year.
As a Riverhouse Homeowner, what action do you propose? We welcome a discussion of the problem in the comment area below.