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.
One of the interesting ants that I am seeing more commonly in landscape settings is the Trap jaw ant (Odontomachus sp.). This ant is so named because of it’s large mandibles (mouthparts) that spring shut capturing prey. These mouthparts can also be used as a defensive mechanism allowing the ant to spring away from something it encounters.
Trapjaw ants. Photo by MSU Ag Communications/Kat Lawrence
A nesting area is very recognizable after you have seen one because it looks like a collection of soil and small wood debris piled at the base of plants or old stumps. I have encountered nesting areas around living shrubs in many mulched areas of the landscape and under pots sitting on old tree stumps.
Nesting debris from the Trapjaw ants at the base of a Princess flower. Photo by Beth Bolles, UF / IFAS Extension Escambia County.
My first experience with the trap jaw ant was not very pleasant. I was working in a mulched area pulling a few weeds without gloves. I unknowingly disturbed the nest and received a pain sting similar to a paper wasp sting. The discomfort was short-lived and I personally did not have inflammation or inching a few minutes later. Of course, I identified the ant and have since become very familiar with recognizing nesting spots.
Although trap jaw ants are not native to our area, they do not rank in the same category as fire ants which are both economically and medically problematic. Since trap jaw ants are currently found in more natural areas of the landscape, homeowners should just be aware of their presence. Consider a pair of gloves or garden tools when rooting around in mulch. When a nesting area is disturbed, the large ants (about .5 inches) will be easy to observe as one of the more interesting ants we may encounter.
The UF/IFAS Extension and FAMU will be bringing the Florida Pest Management Conference to Milton on April 17th. Attend to earn CEUs for your PCO License. Attendance is free and we are currently seeking sponsors at $80 per sponsoring business/organization. For more details and to register, please visit the conference webpage at Northwest Pest Management Conference.
One of the incredible benefits of living in Florida is exposure to the biodiversity of our wildlife population. From ordinary squirrels and mockingbirds to the more exotic panthers and migratory tropical birds, it is rare one can step outside the house without seeing or hearing wildlife of some variety. One of the practices we “preach” here at Extension is to provide habitat for wildlife in our yards and gardens. While cities and neighborhoods are human-centric, we share these spaces with thousands of wild animals, birds, fish, and insects and should always consider them in our actions.
Attracting birds and butterflies are popular pastimes, and Extension faculty can provide a tremendous amount of information on their preferences and food sources. However, a few unsung critters deserve homes and space as well. Just yesterday, I took a call from a gentleman who was excited to discover a small colony of bats roosting in a tree on his property. He was looking for ways to encourage them to stay, because he realized the countless benefits they provide in free insect control. Many people are nervous around bats of because of their unpredictable, irregular night flight pattern and association with scary stories. However, an average Florida bat can eat 1,000 insects a night, keeping pest populations down, reducing mosquito-borne disease, and saving millions of dollars in crop damage.
In our demonstration garden today, I was delighted to walk up on a black racer sunning itself in the grass. These common garden snakes provide valuable pest control of rats and mice, and are not aggressive or venomous. The fear of snakes often comes from the surprise of finding one unexpectedly, so always be alert and observant when outdoors. Respect for these creatures and a basic working knowledge of common venomous and nonvenomous species can go a long way towards calming one’s nerves. An excellent resource for snake identification in north Florida is this online guide. Like many snakes, this particular snake had been in tall grass, so it is always wise to be cautious in those areas.
This black racer sunning in the grass must have gotten the message about utilizing habitat provided for wildlife! Photo credit: Carrie Stevenson, UF IFAS Extension
To attract wildlife, learn about their life cycle and food sources, and provide shelter, water, and food for the species you are interested in attracting. Keep in mind that inviting wildlife may also draw their predators, but know that this is part of the larger cycle. Always keep safety in mind, and if necessary keep tall vegetation and deep water to a minimum in play areas frequented by young children. The benefits of providing food and shelter for wildlife are countless for human observers and wildlife alike.
Many gardeners plant a spring vegetable garden with a number of different vegetable types, which is excellent because a diverse and varied garden is proven to improve soil health. Intercropping is a gardening practice of growing different crops in the same field. When planting a mixture of crops in the same field year after year, it is important to rotate the location of each type of vegetable. This is a practice known as crop rotation. Intercropping and crop rotation will help reduce insect pest populations, increase beneficial insect populations, and reduce weed populations .
Including plants that pest insects don’t like to eat in a garden forces the pests work harder to find what they find palatable. Studies have found reduced whitefly numbers on squash plantings mixed with a crop of buckwheat when compared to squash planted alone. Another crop mixture that may be unintentional, but may be favorable, is a crapemyrtle stand along a garden’s edge. Crapemyrtles will attract the crapemyrtle aphid which will attract predatory insects. When the predatory insects run out of crapemyrtle aphids to eat, they will move to the vegetable garden and begin to hunt pest insects.
Squash with living mulch of buckwheat. Photo Credit: Oscar Liburd, UF/IFAS Extension
A trap crop is a plant that attracts a pest insect away from your food crops. Trap crops work best when planted at the garden’s edge, along a fence row, or in movable containers. A bare space, let’s say 5 feet or so, should be kept between trap crops and vegetable plantings. This will help keep the pests from moving desirable crops plants. When a large population of pests are found on the trap crop then it is time to spray them with insecticide, or cut the crop down and remove or destroy the debris. If trap crops are planted in containers, then it makes them much easier to remove from the garden when necessary.
Cover Crops and Green Manure
Soil organic matter can be increased by the use of green manure and cover crops. Cover crops are generally planted during the off-season, but they can be planted in between vegetable rows and tilled in at a designated time as a green manure. Both cover crops and green manure improve garden production by:
- Suppressing weeds by competing for water, light, and nutrients;
- Holding the soil in place and preventing erosion;
- Scavenging for nutrients that can be utilized in future crops;
- Reducing nematode populations;
- Providing a habitat for beneficial insects.
A mixed plot of cover crops and trap crops. Photo Credit: Matt Lollar, UF/IFAS Extension – Santa Rosa County
A number of different crops can serve as cover crops or green manure crops. Most are legumes (bean family) or grasses. A few that should be tried are:
- Sunn hemp
- Winter rye
More detailed information on cover crops and green manure can be found at this link: http://edis.ifas.ufl.edu/aa217.
You never know what you’ll find when you start looking closely in your garden. I was puzzled as to why there were three dead leaves hanging together on my sweetbay tree when all the other leaves looked so nice and healthy. On further investigation, I found a cocoon was made by binding the leaves together and it was firmly attached to the branch with silk.
The hanging dead leaves are a perfect hiding place for the cocoon of the sweetbay silkmoth. Photo credit: Mary Salinas.
This is the cocoon of the Sweetbay silkmoth, Callosamia securifera. Adult females lay their eggs on the native sweetbay tree, Magnolia virginiana, as the caterpillars only feed on sweetbay leaves. The trees tolerate having a few leaves eaten so there is no need to pick off the caterpillars if you find them. Local birds may do that for you as they rely on an abundance of caterpillars to feed their baby birds.
See photos of this beautiful moth with more details on its life cycle.
And then explore Gardening with Wildlife on UF/IFAS Gardening Solutions.