Question of the Week Number 1: July 6, 2017
“Neil, what are these little insects that are all over my euonymus shrubs? It looks like they’re killing them.”
First things first. Most folks misidentify euonymus shrubs. The quick ways to ID the shrubs themselves are by their very glossy leaves (most species), many with highly variegated gold or silver leaves and rounded lobing around the leaf margins.
As for the euonymus scale, this insect is extremely common with all shrub-form types of euonymus. It may take a few years for it to show up, but it almost always does. The plants begin to thin and show browning leaves, then you start noticing the crusty white pests on the leaves and twigs. The insects are extremely prolific, and within a few months sections of the plantings begin to die out entirely. By then it’s usually too late to save the rest of the plants unless you’re willing to look at unsightly gaps.
• Horticultural (dormant) oil sprays applied in late winter offer the best means of keeping populations under control. But even they aren’t completely dependable.
• Systemic insecticides may offer help during the growing season.
• Summer-weight oil sprays can be used to slow populations during the growing season. However, follow label directions implicitly to avoid damage to foliage due to sunlight and high temperatures.
• In all honesty, growing euonymus shrubs in Texas is a slippery slope. If there are other shrubs you can choose, you’d be well advised to do so. And I have a hard time recommending expensive repetitive treatments to plantings that are heavily infested. You’d be better advised to invest those same dollars in replacement shrubs of other species.
Note about wintercreeper groundcover…
I’ve been growing purple wintercreeper euonymus groundcover for 30 some years in my own landscape. It’s also quite common in thousands of commercial and residential landscapes where we have traditionally used Asian jasmine in the past. Most of the times when I have observed euonymus scale to be a problem on wintercreeper have been when it was allowed to escape its groundcover status and grow up fences and tree trunks. As a groundcover growing flat on the ground, I’ve only encountered a scale issue one time and it was easily stopped.