by Carrie Stevenson | Jul 19, 2016
Florida home and yard. Home, house, stone pavers, walkway, yard, landscaping. UF/IFAS Photo: Tyler Jones
Dr. Ramon Leon, Extension Weed Specialist, West Florida REC, Jay
Last year the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) classified glyphosate as “probably carcinogenic to humans.” This generated a lot of controversy because the Environmental Protection Agency (EPA), the European Food Safety Authority, and recently a joint report between the Food and Agriculture Organization (FAO) and WHO concluded that glyphosate is unlikely to be carcinogenic in humans.
As a University of Florida/IFAS Weed Specialist, I have been receiving multiple phone calls and e-mails from homeowners, homeowner associations (HOA), lawn care companies and contractors, municipalities, and county managers requesting a list of herbicides that are “safer” than glyphosate. When I ask them the reason for this particular preference, all of them acknowledged that their concern originated from hearing about the IARC report.
The first point that I always explain to people concerned about this issue is that most of the scientific evidence indicates that glyphosate does not have a higher carcinogenic risk compared to many other substances that they are normally exposed to in their daily activities. The second point is that it is important to continuously monitor how chemicals we use affect our health and the environment in the long run. The IARC report is a reminder that we should keep a close eye on glyphosate, the most widely used herbicide in the world, but it is not necessarily a call to stop using it, because at this point there is no direct evidence that it causes cancer in humans.
Very frequently, regardless of the technical details, many homeowners and citizens in urban areas are considering not using glyphosate in their gardens and landscapes, and they would like to use “safer” herbicides.
What do you mean by “safer?”
If you mean lower risk as a carcinogen, then most herbicides registered for use in urban areas would be acceptable because none of them are considered “probably carcinogenic” by IARC or any other regulatory agency. Therefore, you have multiple options to choose from. However, many of the conversations have lead to the statement, “No, I want something that is less toxic than glyphosate!”
Toxicity in pesticides is predominantly assessed using the lethal dose 50 (LD50), which indicates the amount of a chemical that kills 50% of a reference population of test animals (e.g. mice, rabbits, rats). When the LD50 is high, this means that the chemical has low toxicity, and when the LD50 is low it is considered that toxicity is higher because small amounts of the chemical can cause mortality. Glyphosate has one of the highest LD50s for herbicides. In other words, glyphosate is one of the least toxic herbicides available based on the LD50 standard. Therefore, if we want an alternative herbicide that is less toxic, we do not have any options for urban areas.
What about organic herbicides?
Many people associate “organic” with “safer.” This can be misleading because it depends on how safety is measured. For example, there are multiple organic herbicides that are considered to have the same or even higher toxicity when compared with glyphosate, because many of them have irritant and corrosive properties. Furthermore, organic herbicides have dramatically different herbicidal properties that make them unlikely alternatives to effectively replace glyphosate.
Glyphosate has one of the broadest spectrums of control, so it kills many different weed species effectively. Also, glyphosate works systemically. This means that it is absorbed by leaves and then moves inside the plant to growing points, roots, and other propagating structures. This systemic effect increases the ability to kill relatively large plants. In contrast, the majority of organic herbicides have a contact effect, so they only kill the tissue they touch without being able to move inside the plant. Therefore, they are effective at killing very small plants (<2 inches tall). Large plants can suffer leaf burning after treatment with organic herbicides, and if the application is done properly, the user will see a lot of control shortly after the application (Fig. 1). However, the plants will soon recover and the control level will decrease because, unlike plants treated with systemic herbicides, they can produce new growth from tissues that were not directly expose to the herbicide.
Figure 1. White clover (4 inches tall) control after treatment with glyphosate and twelve different organic herbicides based on natural oil extracts from plants. The green bars represent the level of control 7 days after treatment (DAT) and the yellow bars indicate control 21 DAT.
Considering the lack of alternatives to replace glyphosate, if you want to stop using this herbicide, and you do not want to use any other synthetic herbicides, because their toxicity might be higher, then you need to recognize that weed management will be more challenging. It is unfair to ask lawn care companies or members of HOAs to stop using the tools they have to control weeds and yet expect “weed free” lawns, gardens, and landscapes. Controlling weeds in these scenarios without glyphosate and other synthetic herbicides will require more intensive use of mechanical control approaches and hand weeding. Also, if relying on organic herbicides, these herbicides will have to be frequently applied (probably once or twice a week) in order to kill the weeds at the right time (before they get too big). Also, all these activities will increase weed control costs and the results will likely be not as satisfactory. Thus, you might end up paying more to have lawns and landscapes that will have more weeds escaping control. If this is not acceptable to you, then you probably should be more open to consider the weed control tools we have available. Also, you should be more vigilant about what are the appropriate ways to use them to minimize their risks to humans and the environment, while obtaining the benefits that you are seeking. Otherwise, you should get used to seeing more weeds in the landscape, and to be fair… this might not be as bad as some people think.
by Molly Jameson | Jul 19, 2016
Carrots and squash at the Lake Ella Growers’ Market. Photo by Jennifer Taylor.
When you think of farmers’ markets, what is that comes to mind? Is it the customers perusing the tables, the vendors organizing their displays, the variety of colors of the fruits and vegetables, the aromas of many types of baked breads, the pop-up tents forming a loose circle…? Or is it all of these things wrapped up in a sense of community?
Honey from Mac’s Honey and Bee Farm. Photo by Molly Jameson.
If you have not experienced a farmers’ market that evokes such senses, then you should stop by one of the farmers’ markets where vendors selling the produce actually grew it themselves. These markets are often referred to as growers’ markets.
Still not convinced? What is it that you are looking for? Liven up your summer dinner table with fresh blueberries grown in Monticello, sweet corn that hardly needs cooking, flavorful heirloom tomatoes, freshly dug potatoes, lime-green field peas, cucumbers with a crunch, sweet yellow onions, multi-colored oblong peppers, juicy garlic, yellow crook-neck squash, dark green zucchini, shitake mushrooms harvested off oak logs, herbs just picked that morning, edible flowers….
The adjectives used to describe the produce may seem like an exaggeration until you really dive into these flavors and learn about how they were grown, where they were grown, and why the farmer decided to concentrate his or her efforts on the particular varieties. And when you are at a growers’ market, don’t be shy! Ask the farmers what they are growing and the methods they use for farming. What has gone well, what has not. They very well may tell you it’s all in building the soil, conserving the water, and supporting diversity.
Jack from Crescent Moon, selling fresh baked bread. Photo by Molly Jameson.
And don’t just come for the produce. At many growers’ markets, there are so many types of fresh-baked breads and cookies, local wildflower honey, local eggs, grass-fed meats, fruit preserves, hand-made soaps, and dried vegetables and powders.
Some growers’ markets in the Tallahassee area include the Lake Ella Growers’ Market, the Red Hills Online Market, the Frenchtown Heritage Marketplace, and the Sunshine Growers’ Market. If you do not live in the Tallahassee area, visit the Florida Department of Agriculture and Consumer Services Community Farmers Markets locator to find farmers’ markets near you. Take some time to explore your farmers’ markets to see who is growing their own and what markets are growers’ markets. In this way, you can help support local farmers!
by Beth Bolles | Jul 7, 2016
Many of the plants in our gardens have been developed and discovered that offer interesting characteristics. These may include leaves with variegations, dwarf growth habits, or even contorted stems. We enjoy these plant differences and many of these plants are big business in the nursery trade. In nature, it is likely these interesting plant mutations would not survive as they are less likely to be able to reproduce successfully. Horticulture professionals keep these plants available most often by propagation through cuttings and tissue culture.
Sometimes in the landscape, nature prevails and we see one of our favorite plant varieties revert back to its original or “wild” form. You may see a stem on a variegated plant that has larger leaves that are all green.
‘Butterfly’ Japanese maple has beautiful variegated foliage. One stem has reverted to an original form with large green leaves. Prune out this stem. Photo by Beth Bolles
These stems often grow more vigorously and can use nutrients and energy that the remainder of the plant needs. As soon as you see these different stems, prune them back to a connection with another stem that exhibits the plant characteristics you want.
by Mary Salinas | Jul 7, 2016
The Zika virus has made us all more aware of the need to avoid getting bit by mosquitoes when we travel to those destinations that have confirmed reports of Zika infected mosquitoes. The Centers for Disease Control and Prevention lists the countries and territories that have travel notices to consult prior to planning a trip or traveling.
The invasive mosquitoes Aedes aegypti (left) and Aedes albopictus (right) occur in the Americas, including Florida, and have been implicated in the transmission of Zika virus.
Credit: J Newman, UF/IFAS/FMEL
The Florida Department of Health has recommendations for preventative action to take when traveling to any location that has confirmed Zika virus.
- You should use an insect repellant (following all label instructions) with any of these active ingredients:
- DEET
- Picaridin
- Oil of lemon eucalyptus
- Para-menthane diol
- IR3535
- Wear long-sleeved shirts and pants
- 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.
According to the Georgia Department of Public Health you should also protect yourself against mosquito bites for at least a week after you return home from any location that has confirmed Zika. You may have an active infection without symptoms that can be spread to others through mosquito bites.
Now let’s talk about mosquito control in your own landscape.
Even though we don’t have confirmed Zika infection in Florida mosquitoes at this writing, mosquitoes in our state can transmit other diseases such as: eastern equine encephalitis, dengue fever, dog or cat heartworm, chikungunya, malaria, St. Louis encephalitis and west Nile virus.
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:
Zika, a Mosquito-Transmitted Virus
Mosquito Repellents
UF/IFAS Mosquito Information Website
Florida Container Mosquitoes
by Mary Salinas | Jul 7, 2016
Peppers and tomatoes are in the same plant family – solanaceae or more commonly known as the nightshade family – and can be susceptible to some of the same diseases. This is true of Tomato Spotted Wilt Virus (TSWV). The solanaceae family includes potatoes, eggplant, tobacco, petunia, tomatillo and deadly nightshade in addition to pepper and tomato.
Pepper with TSWV. Photo credit: Mary Derrick, UF IFAS Extension.
This virus is spread by very small insects known as thrips. They acquire the virus as larvae when feeding on an infected plant and then transmit the disease when they fly to other susceptible plants as adults.
Initial symptoms are yellowing and distortion of the leaves. The leaves can also display yellow or brown circular ring spots. The severity of the virus can depend on the particular cultivar of pepper, its age and the environmental conditions in which the pepper is growing. Fruit can develop yellow, brown or ring spots as well.
TSWV infection showing ring spot on leaves and lesions on fruit. Photo credit: Mary Derrick, UF IFAS Extension.
If you think your pepper has TSWV, consult your local extension agent to confirm the diagnosis. But once infected, there is no treatment for the plants and they should be pulled up and disposed of in the trash to prevent other susceptible plants from becoming infected.
For more information:
Some Common Diseases of Pepper in Florida
