Dr. Ramon Leon, Extension Weed Specialist, West Florida Research and Education Center
Herbicides simplify weed management by allowing you to cover extensive areas in a relatively short time, and reduce the need for time-consuming control practices such as hand weeding. Additionally, many herbicides have the advantage of selective control. Selective herbicides are those that kill weeds without significantly injuring the desired plant. In turfgrass, selective herbicides are particularly important because we do not have the option of using cultivation or non-selective herbicides, as is commonly done in other agricultural systems such as row crops and orchards.
A common misconception is that when a herbicide is registered for use on a given turfgrass species, this herbicide has little negative effect on the turf. In reality, even when the herbicide is registered for a specific turfgrass species, it can cause a certain level of injury. If the herbicide is applied at the recommended label rate, and the growing conditions are ideal, the turfgrass will only suffer minor, temporary injury that may go completely unnoticed. Conversely, the weeds that are susceptible to the herbicide will be severely affected resulting in the desired control.
Over the last few summers, there has been an increase in complaints about herbicide injury on sod farms, golf courses, and home lawns after applications of herbicides, especially during the summer months. Many of those complaints originated from situations in which the application was done properly, using the recommended label rate, and thus the level of injury observed was not justified. After studying all these cases, it was determined that at the time of herbicide application the turf was under a moderate level of stress, but not high enough stress to cause visible symptoms. However, when the herbicide was applied the combined effect of the existing stress, and the stress caused by the herbicide made it harder for the turf to maintain the desired quality. For example, Figure 1 below shows that the turf looked fine before the application (A), but after the herbicide was applied, there was a significant loss in turf cover and quality (B). The interesting aspect is that the injury was not present across the entire treated area, but only on patches (C). Those patches corresponded with sand pockets where soil moisture, especially on hot days, was considerably lower than the rest of the area. In that particular case, the irrigation system was providing enough water to help the turf tolerate the moderate stress of high temperatures and limited moisture, but not enough for the turf tolerate the combined stress that occurred after the herbicide was applied.
Figure 1. Centipedegrass growing during the summer in Florida before herbicide application (A), 3 weeks after herbicide (sulfentrazone and metsulfuron-methyl) application (B). Herbicide injury pattern with highlighted areas showing where sand pockets caused drought and heat stress that contributed to herbicide injury (C).
In Florida, there are a combination of environmental factors such as high temperatures and sandy soils that can create stressful conditions limiting turfgrass growth, especially when irrigation is not sufficient to keep the turf hydrated. Furthermore, we also experience periods of excess rainfall, and areas of turf growing under shade. Additionally, pest problems that affect roots and leaves are frequently found in our state. All these conditions affect turfgrass health and its ability to tolerate herbicide applications. For these reasons, turf producers and managers need to be proactive to help turfgrass overcome the injury that herbicides might cause. To achieve this goal, you need to follow five simple steps:
1) Identify weed problems early. Most weed problems will start in the spring for summer weeds and in the fall for winter weeds. Controlling them when they are small not only increases the effectiveness of our applications, but also allows us to implement our control when the turfgrass is less likely to be stressed.
If herbicide applications are needed when conditions might be stressful for the turf (high temperatures and/or dry conditions)
2) Make sure irrigation is adequate (increase frequency or duration if needed) for up to three weeks following application.
3) Reduce mowing frequency and increase mowing height 0.5 inches for up to 3 weeks following a herbicide application, to allow the turfgrass to continue producing energy to support its recovery. Mowing too short and too frequently immediately after the application weakens the turfgrass.
4) Fertilize with a small amount of nitrogen (0.25 to 0.5 lb N/acre) a week or two after herbicide application to help the turf recover and produce new leaves.
5) If the turfgrass is suffering from serious pest problems (pathogens, nematodes or insect infestations) do not apply herbicides on the affected areas until the turfgrass has recovered.
Maintaining optimal turfgrass growth is the best way to ensure that herbicide applications will maximize weed control while still protecting the health and aesthetics of your turfgrass.
For more information on growing turfgrass in Florida, please see the following:
When watering to establish a lawn or when renovating (redoing, patching, reestablishing, starting over, etc.) a lawn, we normally call for 2-3 “mists” throughout the day for the first 7-10 days until roots get established. These are just 10 minute bursts. Then back off to once a day for about ½ hour for 7-10 days. Then go to 2-3 times a week for about 7 days. By then your lawn should be established.
Of course, if we are experiencing adequate rainfall, you may not need to irrigate. Rain counts. But in the absence of sufficient rain, you’ll need to provide enough water at the correct time to allow your new sod to root – hence, the above directions.
A well designed and correctly installed irrigation system with a controller, operated correctly, really helps to achieve uniform establishment. It can be very difficult or impossible and inconvenient and time consuming to uniformly provide sufficient water to establish a lawn with hose-end sprinklers, especially if the lawn is sizeable and during dry weather. Most people are not going to do the necessary job of pulling hoses around on a regular basis to result in a well established lawn.
There is no substitute or remedy for incorrect irrigation when establishing a brand new lawn or when renovating an entire lawn or areas within a lawn.
It would be wise to not invest the necessary time and money if the new lawn cannot be irrigated correctly. Taking the gamble that adequate (not too much, not too little) rainfall will occur exactly when needed to result in a beautiful, healthy, thick, lush lawn is exactly that – a gamble.
An irrigation system is nothing more than a tool to supplement rainfall. As much as possible, learn to operate the irrigation controller using the “Manual” setting. It is also wise and is state law to have a rain shutoff device installed and operating correctly. The rain shutoff device overrides the controller when it is raining or when sufficient rainfall has occurred. Rain shutoff devices are relatively inexpensive and easily installed. Also, a good rain gauge can be an inexpensive tool to help you monitor how much rain you’ve received. Rain counts.
Too much water will result in rot, diseased roots and diseased seedlings and failure. Too little water will result in the sod, seedlings, sprigs or plugs drying excessively and failure to establish. The end result at best is a poorly established sparse lawn with weeds. Or complete failure.
For additional information on establishing and maintaining a Florida lawn, contact your County UF/IFAS Extension Office or visit http://hort.ufl.edu/yourfloridalawn.
Setting the sprinkler head for an irrigation system. UF/IFAS Photo: Josh Wickham
Lawns and landscapes require water to flourish and provide the green surroundings desired around homes and recreational areas. Often nature provides water for the landscape in the form of rain, but that is not always adequate. Turf and ornamental plants in the establishment stage need supplemental irrigation during hotter months, especially in the sandy soils of northwest Florida, which can dry out at a rapid pace. February is typically a time when very little supplemental irrigation water is needed because most of the desired landscape plants and grasses do not use much water in the cooler temperatures. The warmth of spring and the heat of summer are around the corner and preparations should be made now to ensure that irrigation systems are working properly before being needed. Here are a few things to think about when prepping irrigation systems for spring:
Maintain, Repair, or Replace the Rotors, Nozzles, and Heads. Many sprinkler heads get damaged over time from riding lawn mowers, utility workers, vehicles, or other causes. To avoid having a geyser in the irrigation zone, it is a good idea to test run the system to make sure the rotor and heads are working properly and the nozzles have not been knocked loose. Many times broken rotor or spray heads can be replaced simply by taking the interior mechanical parts out and replacing them with new parts. This may not even require digging! Sometimes repairs are as simple as replacing a filter or spray nozzle that has popped off over time.
Calibrate the system to provide 1/2 inch to 3/4 inch during an irrigation event. Many Florida homeowners and horticultural professionals apply too much or too little water while irrigating. Most do not even know how much irrigation water is being applied. It is important to calibrate the irrigation system to apply only 1/2 inch to 3/4 inch of water during an irrigation event to promote a healthy lawn and landscape. To little water will stress the plants while too much water may promote disease and insect problems. Irrigating improperly may also cause environmental issues, from soil and fertilizer runoff, to develop. Watch this short video on irrigation calibration.
Inspect and make sure the Rain Shutoff Device is working properly. In Florida, it is state law to have a rain shutoff device on an automatic irrigation system. Most systems have a device installed that utilizes a small cork disc that expands when wet and physically clicks a button to tell the system to skip the next automatic cycle. As the cork degrades over time, it will cause system malfunction and should be replaced periodically. It is best to skip using an automatic timer and instead watch the weather and the plants for symptoms of drought stress. If an automatic timer is used, a functioning rain shutoff device is essential for proper irrigation management. Other types of shutoff devices are available as well.
The following University of Florida / IFAS publications contains more information on proper irrigation management for landscapes:
Late summer brings hot, humid temperatures, and many Floridians are retreating from the heat into their air-conditioned homes. Unfortunately, those comforts of home also come with a price tag. When people think about energy efficiency, practices like turning off lights, purchasing energy-efficient appliances, good insulation and windows, and managing A/C temperature settings are the first things that come to mind. These are very important steps to take, not only to save money but also to conserve energy. The US Department of Energy has an excellent publication that can take you step-by-step through a home evaluation, and many energy companies offer a similar walk-through energy audit for free.
However, there are many best management practices that can be done outdoors to offset expensive home power bills. Planting trees is one example. Department of Energy studies have shown that when compared to a home in full sun, a shaded home may experience up to a 25% decrease in energy for cooling.
This home uses passive cooling from a front porch and numerous shade trees. Photo credit: Carrie Stevenson
Trees planted to shade eastern and western facing walls of your home can be the most effective, as these areas receive direct sun in the morning and afternoon. By preventing heat from entering your home, you prevent straining an air conditioning system that would otherwise have to counteract that heat. It is also helpful to provide shade over an air conditioning unit. Deciduous trees are ideal, as they have leaves to provide shade in the summer but drop them by winter, when you might want sunlight to passively heat your home.
In addition to shade, transpiration—the process of plants emitting moisture as they release water from leaf pores—creates cool spaces around vegetation. Grasses and shrubs along the edges of a home, or vines on nearby trellises, can cool walls and windows in this manner.
Finally, consider sprinkler systems. A home irrigation system can use a significant amount of energy to pump water throughout your yard. Calibrating your system and even reducing run time or frequency can also conserve water and reduce water bills.
For more information on energy-efficient landscaping, please visit www.myfloridahomeenergy.com or contact your local Extension office.
If you’ve been gardening for more than a few years, you may be confused by UF/IFAS recommendations that conflict with practices you’ve used for years. You aren’t imagining things, we do change recommendations based on the most current research available to help you with your agricultural endeavors.
I want to share a few common mistakes that gardeners make based on old recommendations but that research has shown are not the best choices. Check out the list below to see if you can break an old habit or two!
Old Habit
Current Recommendation
Throw a little “starter fertilizer” in the hole (or under new sod, seed, etc.)
It is not beneficial to add fertilizer to plantinghole or under newly installed sod.Quick release (soluble) fertilizer may burn roots if added to planting hole.If applied properly, a slow release fertilizer may be applied to trees and shrubs but should be applied to the top of root ball or mulch following label instructions.Turfgrass grown from seed, sprig, or sod does not use fertilizer efficiently at planting. Wait 30 days to apply fertilizer – after roots have been established.
Dig the hole twice as deep and wide as the root ball for trees and shrubs
1.5 times the width of the root ball is good, but planting too deep can be a death sentence.Planting depth should be 10% shallower than the distance from the topmost root to the base of the root ball.
Mulch 3-5 inches deep
2-3 inches with a very thin layer directly over the rootball (less than 1 inch) and none touching trunk. This is the ideal amount to conserve water and suppress weeds.
Native and drought tolerant plants don’t need water
All plants need water until established – depending on the type and size of the plant, weather, and soil conditions this may take months.Always plan to give a little TLC to newly installed plants no matter how tough they are supposed to be.
With the over abundance of rainfall the western panhandle has seen in recent weeks, tomato gardeners need to be aware of foliar diseases that could appear. Tomato leaves are an ideal host when moisture is present on the leaf surface. There are several of these diseases that, if not managed, can destroy the garden.
Early Blight
Advanced symptoms of Early Blight (Photo Credit: UF/IFAS U-Scout website)
Early Blight is a fungal disease that can affect tomato leaves and fruit. The disease is most prominent when temperatures are 80°F and excess moisture is present from rain or irrigation. The most classic system is the presence of leaf lesions that are approximately 1/2 inch in diameter.
Bacterial Spot
Bacterial Spot on a Tomato leaf (Photo Credit: Hank Dankers, From U-Scout)
Bacterial Spot can also cause problems for Florida tomato gardeners in rainy and high temperature periods. Generally the symptoms are darkened circular lesions on the leaves and fruit. Sometimes bacterial spot can be confused with other leaf lesion diseases. The bacterial spot will ooze when cut where as fungal type lesions will not.
How to prevent foliar diseases in tomato:
Always start with disease free seed and transplants.
Irrigate early in the day to minimize the time the leaves stay wet. Use drip irrigation when possible.
Remove blighted leaves when the garden is dry. This technique should not be relied on exclusively.
Remove and destroy crop residue at the end of the growing season. If not removed, it can become a breeding ground for disease next year.
Rotate to different plant families that are not affected by the same diseases.
Spray protective fungicides such as Mancozeb, Copper, and Chlorothalonil (for example sold as Daconil) when the conditions are right for disease (higher temperatures, excessive moisture, and rainfall).
If you have questions about these diseases or other tomato diseases, please comment below or call your local UF/IFAS Extension Agent.
