Posted by Mary Small, CSU Extension Master Gardener Coordinator
With that title, you might wonder about me – yes, I’m aware
it’s still March! And dealing with those guys is a bit down the road yet. But
here’s the deal:
I recently returned from a family gathering in Missouri.
While there I was asked about a plant problem. I’m usually pretty wishy-washy about
identifying out of state plant problems because conditions and pests can be so
different. But I fearlessly dove in. It went something like this.
FM (Family Member): What would make the leaves on a rose
look lacy? Do you think the recent cold weather would kill it altogether? (I determined she
meant would the cold have killed the overwintering stages.)
Me: (visibly annoying the FM by not giving an immediate,
decisive answer): It sounds like
rose slug to me, but I don’t know what pests you have here. I really need to
figure out what the pest is first.
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| Lace bug damage, Whitney Cranshaw, CSU Extension |
FM: The garden center said it was lacebug. They feed on the
leaf undersides – and it’s hard to treat there, so I’m not sure I killed them.
Me: (While hastily looking up symptoms of lace bug damage on
that state’s Extension web site): Did the garden center staff person see the
damage?
FM: No, but that’s what they thought it was.
Me: Well, here’s a picture of lacebug damage. Is this what
it looked like?
FM (looking at the pictures on my phone): Well, not quite, well,
maybe. Maybe there are still some leaves under the roses that you can look at.
Me: (Trudge outside, poke around under the rosebushes and find
some leaves with- ta da- pretty
heavy-duty rose slug damage. Go inside and show my “find”.) “Is this the damage
you were seeing?”
FM: Yes, that’s it!
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| Rose slug damage, Ask An Expert |
Me: Okay, you have rose slugs, not lacebugs.
FM: Will the pesticide in the garage kill them?
Me: Trudge out to the garage – mercifully there is only one
pesticide to examine. It contains spinosad and roses are on the label. Woo hoo
– the FM’s good to go with their annihilation plans.
Then the pesky overwintering question- and I found the
answer in a research-based source - “When spraying, be sure to spray both sides
of the leaf and the ground below the plant as the larvae pupate in the soil
prior to overwintering.”
Having not taken some of these steps, the FM will need
to do a bit of scouting this spring for the newly emerged larvae. Then treat,
continue to scout and possibly re-treat.
This late winter- time exchange reminded me the importance of one
of those early diagnostic steps – “examine the plant”. And while I kinda doubted lacebug was
the culprit – I checked my research-based resources to confirm. This story will
come in very handy shortly when I teach our Master Gardeners about the
diagnostic process.
And now I better send off the information about rose slugs
to the FM.
