In the garden with Felder: Keep watch for sap-sucking bugs on your crape myrtles

 

Mississippi gardens are facing a tough opponent — serious sap-sucking insects called crape myrtle bark scale.

Mississippi gardens are facing a tough opponent — serious sap-sucking insects called crape myrtle bark scale.
Photo by: Felder Rushing/Courtesy photo

 

 

Felder Rushing

 

 

Sorry to be the bearer of bad news, but Mississippi gardens have just started getting a little less rosy.  

 

While I rarely get into diagnostic stuff in this column, I'm seeing a lot of something new and bad enough to have landscape experts worried; need to nail down early what can be done.  

 

Not talking about usual hard-to-treat calls we horticulturists dread getting, such as bad weeds, sudden midsummer "browning out" of healthy-looking shrubs or trees dropping old limbs or leaking sap from their trunks.  

 

Both are usually related to severe root or lower trunk problems, often having built up over several years. Azaleas, Japanese hollies, roses, Eleagnus, junipers and other shrubs with weak roots can't take back to back long wet and dry spells, and often pop their corks in midsummer heat.  

 

Older trees usually have internal decay caused by fungi that get into interior wood through broken limbs, improper pruning cuts, lightning, insect holes, or even tiny cracks that occur during strong winds and ice storms. Happens to young trees damaged by mowers or string trimmers.  

 

It might take years for affected shrubs or trees to die, and there's not much we can do except replace the dead with new ones, being careful to rework and widen holes, and, crucially, loosen the potting soil and roots of new plants so they can quickly adapt to your garden soil. 

 

And with older trees, simply prune out dangerous limbs and hope to get a few more years from what's left.  

 

But the really big thing that has us worried is a serious sap-sucking insect found on crape myrtle trees for the first time in Mississippi less than four years ago; it's already all over the place, and control is pretty difficult. 

 

Called crape myrtle bark scale, the tiny legless white or grayish bugs have insecticide-resistant waxy shells and cover twigs, branches and trunks of trees, sometimes a few at a time but often in crusty masses.  

 

They produce a sticky, plant-sugary excrement, just like the stuff aphids and mites drip from undersides of leaves of crape myrtles, oaks, hackberries, gardenias and a few other plants. A distinctive black "sooty mold" develops on the drippings, covering everything underneath.  

 

No way to prevent aphids and mites from attacking plants, and it's not practical to spray for them; all I do is move my outdoor furniture and pink flamingos out from underneath. The mold scrubs off with soapy water, or eventually flakes off over winter.  

 

However -- and this is a serious new problem -- if you also see and can scrape off tiny white or grayish bumps on crape myrtle twigs, limbs and trunks, and the black stuff is all over the trunks, it's gonna be scale.  

 

What I'm trying to get across is what all the experts say, that treating for bark scale successfully requires careful timing; you can spray a horticultural oil in late fall or winter to smother overwintering nymphs, or soak the ground underneath plants with "systemic" insecticide -- but only in April, May or June when they are best absorbed into trees.  

 

Reread that last sentence. Treating in the summer or early fall simply has little or no effect. Don't overreact or pay anyone to overreact for you. Wait for the right times.  

 

These problems are real heartbreaks to folks who've invested years in trees and shrubs just to watch them peter out when they are reaching their peak of beauty and usefulness.  

 

But all over the South we're working hard to find a solution to the bark scale. Stay tuned to what the Extension Service recommends. 

 

Felder Rushing is a Mississippi author, columnist, and host of the "Gestalt Gardener" on MPB Think Radio. Email gardening questions to [email protected]

 

 

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