Unexplained Plant Problems? Might be an Abiotic Issue!

by | May 20, 2019 | Best Management Practices, Cold Damage, Disease, Foliage, Freeze protection, General Gardening, Insects, Integrated Pest Management, Ornamental Shrubs, Pests, Shrubs

Spring is a wonderful time of year.  After months of dreariness and bare branches, bright, succulent green leaves and flowers of every kind and color have emerged.  So too, have emerged gardeners and outdoor enthusiasts ready to tackle all their home and landscape improvement projects planned over the winter.  However, this is also the time, when folks first start paying attention to their plants again, that strange, seemingly inexpiable plant problems crop up!

All plant problems can be divided into two categories: biotic problems, or issues caused by a living organism (think insects, fungus, and bacteria), and abiotic problems, issues that arise from things other than biotic pests.  It’s the first category that people generally turn to when something goes wrong in their landscape or garden.  It’s convenient to blame problems on pests and it’s very satisfying to go to the local home improvement store, buy a bottle of something and spray the problem into submission. But, in many of my consultations with clientele each spring, I find myself having to step back, consider holistically the circumstances causing the issue to arise, scout for pests and diseases, and if I find no evidence of either, encouraging the person to consider the possibility the problem is abiotic and to adopt patience and allow the problem to correct itself.  Of course, this is never what anyone wants to hear.  We always want a solvable problem with a simple cause and solution.  But life isn’t always that easy and sometimes we must accept that we (nor a pest/disease) did anything wrong to cause the issue and, in some cases, that we ourselves actually caused the problem to happen in the first place!  To illustrate, let’s consider two case studies from site visits I’ve had this spring.

Cold damage on Boxwood hedge

Three weeks ago, I got a call from a very concerned client.  She had gotten her March issue of a popular outdoor magazine in the mail, in which was a feature on an emerging pathogen, Boxwood Blight, a nasty fungus decimating Boxwood populations in states north of us.  She had also noticed the Boxwoods in front of her house had recently developed browning of their new spring shoots across most the hedgerow. Having read the article and matching the symptoms she’d noticed to the ones described in the magazine article, she was convinced her shrub was infected with blight and wanted to know if there was a cure.  Agreeing that the symptoms sounded similar and wanting to rule out an infection of an extremely serious pathogen, I decided to go take a look.  Upon inspection, it was obvious that Boxwood Blight wasn’t to blame.  Damage from disease generally isn’t quite as uniform as what I saw.  The new growth on top of the hedge was indeed brown but only where the eaves of the house and a nearby tree didn’t provide overhead cover and, to boot, the sides of the hedge were a very normal bright green.  Having gone through a recent cold snap that brought several mornings of heavy frost and knowing that the weeks before that the weather had been unseasonably warm, causing many plants to begin growing prematurely, all signs pointed toward an abiotic problem, cold/frost damage that would clear up as soon as the plant put on another flush of growth.  The client was delighted to hear she didn’t have a hedge killing problem that would require either adopting a monthly fungicide regime or replacing the hedge with a different species.

Damage to ‘Sunshine’ Ligustrum from pressure washing siding with bleach.

The very next week, another client asked if I would come by her house and take a look at a hedge of ‘Sunshine’ Ligustrum that lines her driveway, whose leaves had “bleached” out, turning from their normal chartreuse to a bronzy white color.  This time, having seen similar issues with this particular plant that almost always involved an infestation of Spider or Broad Mites, I figured this was a cut and dry case that would end with a call to her pest control company to come spray the offending bugs.  However, though the leaf damage looked similar, I was not able to locate any existing pests or find evidence any had been around recently, rather it appeared the leaves had been exposed to something that “bleached” and burned them.  Puzzled, I began asking questions.  What kind of maintenance occurs on the plants?  Have you fertilized or applied any chemicals recently?  Nothing.  Then, near the end of our conversation, the client mentioned that her neighbor had pressure washed their house on a windy day and that she was irritated because some of the soap solution had gotten on her car.  Bingo.  Leaf burn from pressure washing solution chemicals.  This time I was guilty of assuming the worst from a pest when the problem quite literally blew in on the wind from next door.  Again, the client was relieved to know the plant would recover as soon as a new flush of growth emerged and hid the burned older leaves!

This spring, I’d encourage you to learn from the above situations and the next time you notice an issue on plants in your yard, before you reach for the pesticides, take a step back and think about what the damage looks like, thoroughly inspect the plants for possible insects or disease, and if you don’t find any, consider the possibility that the problem was abiotic in nature!  And remember, if you need any assistance with identification of a landscape problem and want research-based recommendations on how to manage the problem, contact your local UF/IFAS Extension office.

Daniel J. Leonard
Latest posts by Daniel J. Leonard (see all)