white spots on holly leaves - Ask Extension
There are many oblong white spots, darker on one end, on the backs of holly leaves in my yard. Is this some sort of insect? Will it kill the trees? Th...
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white spots on holly leaves #643326
Asked May 30, 2020, 9:48 AM EDT
There are many oblong white spots, darker on one end, on the backs of holly leaves in my yard. Is this some sort of insect? Will it kill the trees? Thank you!
Montgomery County Maryland
Expert Response
This looks like Cottony camellia scale, (Pulvinaria floccifera), a sucking insect.
It exudes a honeydew as it feeds which fosters the growth of a black sooty mold.
It is showing up in landscapes in many parts of Maryland this year. For this scale, you can treat your plants in June with horticultural oil to help smother the more vulnerable juvenile insects when they first hatch (called "crawlers") and use a slightly more concentrated "dormant oil" to manage overwintering scale in the dormant season (when leaves have fallen from deciduous trees). The product label will guide you as to the dilution (unless it's a ready-to-spray product) and how often to re-apply. Thorough coverage of all plant surfaces, including undersides of the leaves, is important for effectiveness.
If you have a very large holly, spraying may be difficult or impractical. Beneficial insects that prey on scales tend to arrive to control their numbers naturally, so you can also forgo spraying if the scale populations aren't extensive or if you can live with the sooty mold for the time being. Another option would be to hire a landscape professional to apply a treatment for you.
https://extension.umd.edu/hgic/topics/cottony-camellia-scale-shrubs
Marian
It exudes a honeydew as it feeds which fosters the growth of a black sooty mold.
It is showing up in landscapes in many parts of Maryland this year. For this scale, you can treat your plants in June with horticultural oil to help smother the more vulnerable juvenile insects when they first hatch (called "crawlers") and use a slightly more concentrated "dormant oil" to manage overwintering scale in the dormant season (when leaves have fallen from deciduous trees). The product label will guide you as to the dilution (unless it's a ready-to-spray product) and how often to re-apply. Thorough coverage of all plant surfaces, including undersides of the leaves, is important for effectiveness.
If you have a very large holly, spraying may be difficult or impractical. Beneficial insects that prey on scales tend to arrive to control their numbers naturally, so you can also forgo spraying if the scale populations aren't extensive or if you can live with the sooty mold for the time being. Another option would be to hire a landscape professional to apply a treatment for you.
https://extension.umd.edu/hgic/topics/cottony-camellia-scale-shrubs
Marian
