scale bugs on hydrangea - Ask Extension
Cottony cushion or hydrangea scale? They're mostly on the woody stems...Also, what's the most effective intervention?
Knowledgebase
scale bugs on hydrangea #648886
Asked June 10, 2020, 1:37 PM EDT
Cottony cushion or hydrangea scale?
They're mostly on the woody stems...
Also, what's the most effective intervention?
They're mostly on the woody stems...
Also, what's the most effective intervention?
Multnomah County Oregon
Expert Response
Thank you for your inquiry and images.
The insects are holly scale which affects both camellias and hydrangea. The very small brown spot is the scale whereas the larger fluffy white objects are egg-cases.
To manage this scale
1.) Start by crushing all the scale you see. But, because you will miss many, also spray as below.
2.) Next, spray. To do so effectively, target the crawler stage which will soon hatch. Use //
To determine when crawlers present, encircle a branch with double-sided sticky tape above and below one or several scale. Spray when you see tiny dots stuck on the tape.
3.) Apply a dormant oil during the dormant season to kill the adults and youngsters overwintering in cracks and crevices on the shrub.
See "Cottony camellia scale" - http://hortsense.cahnrs.wsu.edu/Search/MainMenuWithFactSheet.aspx?CategoryId=1&SubCatId=4&Pl...
re: "Next, spray. To do so effectively, target the crawler stage which will soon hatch. Use //"
...use //? Was there meant to be a product recommendation or website, or...?
Thank you
...use //? Was there meant to be a product recommendation or website, or...?
Thank you
Uh, oh. Sorry for that glitch.
To spray when the crawlers are present, you can use neem or a commercial insecticidal soap, directed to the stems and the undersides of the leaves.
Do not use a homemade soap concoction as doing so may damage the shrub.
...spent some time picking and destroying scales and egg cases today. That's labor-intensive.
Follow-up questions:
are the egg cases too robust to be affected by insect-killing soap?
these insects seem pretty sedentary; do they travel very far (ie more than 4') in the course of their life cycle?
what are their natural predators?
Follow-up questions:
are the egg cases too robust to be affected by insect-killing soap?
these insects seem pretty sedentary; do they travel very far (ie more than 4') in the course of their life cycle?
what are their natural predators?
Yes, physically removing the visible scale can be labor-intensive. The satisfying part of that is youknow they are cgone!
The adults are "settled;" they don't move after they find a place to feed. They're not susceptible to most sprays because of the hard shell covering.
The crawlers (newly hatched youngsters) are the target for sprays because they have not yet developed a waxy covering. The leaave the cottony egg case andd go to a new place on the lef or stem. Once they've located a choise site, they insert their needle-like mouthparts into the plant tissue and begin to feed. That's the end of their journey; they are literally stuck there for life.
The females die after lying their eggs in the protective cottony material. That cottony substance is disrupted with a direct hit of an insecticidal soap spray or is smothered when coated with a horticultural oil.
And yes, they have natural predators, among them lady beetles and various non-stinging wasps. But things on your shrub are far beyond what naturally-occuring beneficial insects can manage.
That said, don't put any faith in purchased lady beetles.They are collected while dormant and are genetically programed to fly up and away when they come out of dormancy. They leave!
