by Daniel J. Leonard | May 20, 2019
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.
by Mark Tancig | Dec 17, 2018
Native trees, like this Live Oak (Quercus virginiana), provide habitat for various insects fed upon by birds. Source: James Holland, Bugwood.org
Planting native plants is a topic many north Florida gardeners, and subscribers to Gardening in the Panhandle, have seen covered in various ways and formats. It doesn’t take a great leap of understanding to realize that native plants are highly valued by our wildlife, which have adapted to living with these plants for millennia. However, we also get a lot of information about the latest, greatest landscape plant variety, many of which are non-native, and are lured to purchase them by their beautiful flowers and/or foliage. In the wake of Hurricane Michael, the importance of selecting native plants for the landscape becomes apparent when you look around and see whole forests severely disturbed. Furthermore, recent research has shown how much our native wildlife prefer native plants and need them for the best chances of survival.
Eastern bluebirds are an example of a bird that relies on insects. Source: Sandysphotos, Creative Commons.
Why Native Plants?
It’s not that non-native ornamental plants are “bad”, unless they’re the terrible invasive, exotic species like kudzu, Chine privet, etc., it’s just that the food chains that support our wildlife are adapted to native plants. A recent report published in the National Proceedings of Science found that chickadees had far better success fledging young when they foraged landscape areas containing 70% or more native plant cover. The reason for their success was that the insects they feed on utilize native species more than non-native plant species. Does that mean non-natives provide no value? Not necessarily. Non-native ornamental plants can be important sources of nectar and pollen and, as you know from experience dealing with pest problems on non-native plants, they also support insects. Native plants just support more of an abundance of these insects.
Following a large disturbance like Hurricane Michael, many insects, birds, and other wildlife will likely see a decrease in numbers and/or reproductive success due to the loss and/or disruption of native plant ecosystems. As stated in the recent report, restoration of urban areas should prioritize native plants to support local food webs.
The deactivated_site website is a great resource to find native trees for your area. Source: Screenshot, deactivated_site.
The deactivated_site website is an easy way to start putting together a list of potential plants. The website’s Florida-Friendly Plant Database allows users to select the area of Florida they live in, site conditions, plant type (tree, shrub, etc.), and to specify native plants only. It then searches the database for plants that meet those conditions and creates a list of species, along with photos and care information. If you’re thinking about how these trees hold up to storms, you can cross-check that list with UF/IFAS’s Wind and Trees EDIS publication. Of course, if you have any questions along the way, please contact your local UF/IFAS Extension Office.
by Mary Salinas | Oct 20, 2018
A natural disaster such as Hurricane Michael can cause excess standing water which leads nuisance mosquito populations to greatly increase. Floodwater mosquitoes lay their eggs in the moist soil. Amazingly, the eggs survive even when the soil dries out. When the eggs in soil once again have consistent moisture, they hatch! One female mosquito may lay up to 200 eggs per batch . Standing water should be reduced as mush as possible to prevent mosquitoes from developing.
You should protect yourself by using an insect repellant (following all label instructions) with any of these active ingredients or using one of the other strategies:
- DEET
- Picaridin
- Oil of lemon eucalyptus
- Para-menthane diol
- IR3535
- An alternative is to wear long-sleeved shirts and pants – although that’s tough in our hot weather
- Wear clothing that is pre-treated with permethrin or apply a permethrin product to your clothes, but not your skin!
- Avoid getting bitten while you sleep by choosing a place with air conditioning or screens on windows and doors or sleep under a mosquito bed net.
Now let’s talk about mosquito control in your own landscape.
Let’s first explore what kind of environment in your landscape and around your home is friendly to the proliferation of mosquitoes. Adult mosquitoes lay their eggs on or very near water that is still or stagnant. That is because the larvae live in the water but have to come to the surface regularly to breeze. The small delicate larvae need the water surface to be still in order to surface and breathe. Water that is continually moving or flowing inhibits mosquito populations.
Look around your home and landscape for these possible sites of still water that can be excellent mosquito breeding grounds:
- bird baths
- potted plant saucers
- pet dishes
- old tires
- ponds
- roof gutters
- tarps over boats or recreational vehicles
- rain barrels (screen mesh over the opening will prevent females from laying their eggs)
- bromeliads (they hold water in their central cup or leaf axils)
- any other structure that will hold even a small amount of water (I even had them on a heating mat in a greenhouse that had very shallow puddles of water!)
You may want to rid yourself of some of these sources of standing water or empty them every three to four days. What if you have bromeliads, a pond or some other standing water and you want to keep them and yet control mosquitoes? There is an environmentally responsible solution. Some bacteria, Bacillus thuringiensis ssp. israelensis or Bacillus sphaericus, only infects mosquitoes and other close relatives like gnats and blackflies and is harmless to all other organisms. Look for products on the market that contain this bacteria.
For more information:
Mosquito Repellents
UF/IFAS Mosquito Information Website
by Matthew Orwat | Sep 13, 2018
Bare limb tips and clusters of webbing in pecan trees are often the first sign that fall is right around the corner.
This webbing is caused by clusters of the larvae of the Fall Webworm (Hyphantria cunea (Drury)) which is often also called Pecan Webworm. “Fall Webworm” is a bit of a misnomer in our region since they are able to strike in spring and summer thanks to our long growing season. They are most noticeable in the fall thanks to cumulative effects of earlier feeding.
The adult form of the fall webworm is a solid white or white and brown spotted moth that emerges in late March through August in southern climates. After mating they lay orderly clusters of green eggs, usually May through August. Soon after emergence, the larvae begin creating silk webs to protect themselves as they voraciously feed on their various host plants, of which Pecan is most common in Northwest Florida gardens.
Although they are capable of defoliating complete trees, especially smaller ones, most seasons they are kept in check by beneficial insects such as the paper wasp. It is beneficial for small orchards or home growers to scout their trees from June through August. If small webs are observed in young trees, it is best to prune them out with a pole saw or pole pruner and dispose of the branch. Pruning of small branches does not harm the tree, but it may be of no benefit to remove small webs in larger trees, if they are being controlled by natural enemies.
Most home gardens don’t have a practical ability to spray for this insect. For homeowners it is difficult to spray for control, due to the cost of the equipment required to get the spray into the tree canopy. If spraying is an option, many insecticides containing spinosad or Bacillus thuringiensis (Bt) exist. Both of these products target caterpillars while not harming beneficial insect predators that feed on these worm populations. Several more toxic insecticide products exist that will control fall webworm, but they often exacerbate insect problems by killing off beneficial insects that might be controlling other insect pests.
Fall webworm is not usually a serious problem for home gardens. Let natural enemies take care of the problem in most cases.
Supplemental Material:
by Beth Bolles | Aug 2, 2018
Burrow made by the female Cicada killer. Photo Credits: Beth Bolles, Horticulture Agent
During the summer months, landscapes are alive with insect activity. The majority of insects found in home landscapes are not harmful, although the sight of a few may cause some concern. One insect appears to be threatening but is not is the cicada killer, the largest wasp in Florida.
During the warmer months, female cicada killers make ground burrows that consist of several cells for raising a few young. There is an entrance hole, which often remains open, surrounded by a small mound of soil on one side of the entrance. The female makes this ground burrow after mating and then captures cicadas to add to the individual cells. The cicadas will serve as food for the developing wasp larvae that emerge from laid eggs.
Although the females are able to sting, they are not overly aggressive wasps. The males do make more aggressive flights around people but are unable to sting. When enjoying your landscape, just be aware of ground burrows and the flight of the female wasps into the burrows. If you are lucky, you may even see a wasp with a cicada in tow.
Cicada killers should not be treated in most landscapes. If you are unable to tolerate the wasps, you may reduce their habitat by covering open sandy areas with mulch or a groundcover. This does not completely prevent their ability to nest but will certainly reduce suitable nesting spots. For more information on cicada killers visit: http://edis.ifas.ufl.edu/in573.
This article is being revisited as part of our ‘Best Of’ series. August, 2012.
