Clip columbine to undermine the leaf miners

D. emailed us to say that

I sprayed insecticide to prevent leaf miner damage on the columbine but they're a mess of mines, anyway. What now?"

 

Columbine leaf miner can be handled many ways:

ignoring it while it simply runs its course

applying insecticide,

plucking leaves or

cutting the plant back.

Hold it to the light and you can see the little buggers are in there right now. Which brings another control option to mind, the squeeze play...

Hold it to the light and you can see the little buggers are in there right now. Which brings another control option to mind, the squeeze play...

Columbine: It's SO PRETTY when it's blooming, and free of insects. But it's a bit tatty after bloom, insects or no (going, going... at center and right). So Option 4 actually becomes an attractive idea.

Option 1: Ignore it

Columbine leaf miner (one of a couple of insects like a fruit fly; Phytomyza aquilegivora makes serpentine mines and P. aquilegiana makes blotches) is not a threat to a columbine's existence. It's just ugly, a leaf-spoiling nuisance. However, if you are determined to reduce the damage:

 

2: Perfect your timing and insecticide may work

This insect species' larvae come out of the leaf as they complete their mining phase, attach themselves to the plant and pupate in about 2 weeks -- faster if it's warmer, more slowly if it's very cool. Adults emerge as tiny flies that lay eggs on the leaves. There may be two or more rounds of this in spring, until eventually one generation of larvae drops into the soil and remains there until the next spring, to emerge and lay eggs about the time the flower stalks begin to lift above the columbine's foliage.

When each new generation of miners comes out of its eggs the insects quickly chew into a leaf. There the plant itself protects them from contact insecticides. Spray a bit early or late and you miss the first flight of adults and/or the briefly exposed young, and have to make a second pass. Insecticides that are absorbed into the leaf to kill what eats them, can't stop all the damage. So this insect is tough to control that way.

3: Get picky - pluck off every bad leaf as you see it.

Picking off leaves as you see miner damage occur can keep the insect's population down. However, when there is this much mining damage, the insect's already had a good year!

 

4: Deny the pest its meal

Right now (late spring) when most if not all columbine miners are inside columbine leaves, you can simply cut down your plants, then burn or hot compost or steam the clippings inside a plastic bag.

The plant will be fine. Sure, you lose a bit of flower but that's not a big loss as the plant's past its peak bloom. What blooms are left, you can cut for a vase.

Have no fear for the columbine if you cut it to the ground. It will be fine. Below: That thick nub of a root, which can be much larger on a plant older than this yearling, contains a lot of starch and thus a lot of comeback.

 

 

 

 

Its new growth might grow unspoiled by miners, and certainly look neater than the foliage of a stem that's bloomed out or ripening seed. It may even produce a few more blooms.

See it already producing new basal foliage?

See it already producing new basal foliage?

More about columbine problems from Connecticut's Ag Experimental Station

http://www.ct.gov/caes/cwp/view.asp?a=2823&q=377634