Chewing caterpillar damage on St. Augustinegrass Photo by: Steven Arthurs, UF
Tropical sod webworm larvae are destructive pests of warm season turfgrasses in the southeastern U.S. especially in the fall. Commonly referred to as a worm, they are truly caterpillars, the larvae of a moth. Larval feeding damage reduces turfgrass aesthetics, vigor, photosynthesis and density, which is very evident on finer-bladed grasses such as bermudagrass and zoysiagrass. Feeding damage is possible on all grass types however. Adults, a dull brown colored moth about ¾ inch long, rest in sheltered and shrubby areas during the day and are active at dusk. Females deposit clusters of 10-35 eggs on the upper surface of grass blades. The eggs hatch in 3-4 days and develop from a 1 mm long caterpillar to one over 11 mm long through six instars within 21 to 47 days, depending on temperature. Larval feeding occurs at night, leaving the grass looking ragged, shortened and missing.
Sod webworm on soil surface
Photo by: Steven Arthurs, UF
Control should be against damaging larvae, not the flying moths. However, insecticidal soap applications to moth harboring areas can reduce re-population frequency. Soil-drenching soap flushes can be used to find the caterpillars, especially in dry and hot grass areas. Bacterial-based insecticides, such as Bt, Bacillus thuringiensis var. kurstaki or Spinosad, will control sod webworm caterpillars without impacting beneficial species as long as they are applied with each flush of grass growth.
Fall armyworms are also active when the weather turns cooler. They feed any time of the day or night, but are most active early in the morning or late in the evening. The 1 ½ inch long gray and white moth lays about 1,000 eggs in multiple masses on any vegetation. Two to 10 days later, the small caterpillar hatches and begins to grow to nearly 2 inches long over a two week period. The fall armyworm is easily recognized by its dark head marked with a distinct pale-colored inverted Y and the long black stripe running along each side of its body. These aggressive feeders “march” rapidly across grassed areas consuming every above-ground plant part. While bacterial-based insecticides will reduce the numbers, control of armyworms usually requires synthetic insecticides.
Photo by: Jim Castner, UF
The good news is that grass “worms” can be controlled and the blades will grow back. The damage may be devastating to see, but usually not a permanent problem.
As you garden this fall, check out the North Florida Vegetable Gardening Guide, compiled by UF/IFAS Leon County Extension.
Getting into vegetable gardening, but don’t know where to start?
Even experienced gardeners know there’s always more to learn. To help both beginners and advanced gardeners find answers to their questions, the UF/IFAS Leon County Extension Office put together the North Florida Vegetable Gardening Guide. It incorporates multiple resources, including articles, planting calendars, photos, and UF/IFAS EDIS publications.
The North Florida Vegetable Gardening Guide covers the many aspects of vegetable gardening, including how to get started, site selection, insects and biodiversity in the garden, soil testing, composting, cover crops in the garden, irrigation, and more.
You can click here to view the digital version of the guidebook. We also have physical copies of the guide available at the UF/IFAS Leon County Extension Office (615 Paul Russell Rd., Tallahassee, FL 32301).
Happy fall gardening!
Over the last decade or so, the Panhandle has been overrun, and I don’t just mean by the summer beach traffic. Rather, by an aggressive, exotic perennial grass that quickly displaces all native species, is not useful as a forage to wildlife or livestock, can spread by roots or seeds, and has no natural enemies. If you own property in the Panhandle or spend any amount of time on its roads, chances are you have become acquainted with this worst of invasive species, Cogongrass (Imperata cylindrica).
A native of Southeast Asia, cogongrass was introduced into the US in 1912 around Mobile, AL as a hitchhiker in orange crate packing. Then the 1920s, 30s, and 40s, it was intentionally introduced from the Philippines into other Gulf Coast states, including Florida, as a potential pasture forage for livestock. Since then, cogongrass has become one of the most economically and ecologically important invasive species in the US and worldwide, infesting nearly 500 million acres and is now found on every continent.
Cogongrass in Calhoun County, FL. Photo courtesy of Daniel Leonard.
Cogongrass is easily identified in late spring, when the grass throws easily spotted fluffy, white-colored seedheads above the mats of grass beneath. Additionally, patches of cogongrass are almost always noticeably circular in nature, radiating out indefinitely from the initial infestation. A closer inspection of the grass will reveal light green leaves up to 4’ in length, with an off-center, silvery colored midrib (the primary leaf vein that runs from the base of the leaf to the tip) and serrated leaf edges. Underground, cogongrass exhibits a dense underground root system that can reach as deep as 4’. This feature is the primary reason cogongrass outcompetes other plants, withstands any drought, fire, or soil condition thrown at it, aids in its resistance to herbicide activity, and generally makes it very difficult to manage.
The first step in managing cogongrass is prevention. If your property or the property you manage doesn’t have cogongrass, do everything you can to keep it that way. While the species can spread distances through seed dispersal, it is much more frequently moved around by fragmented rhizomes hitching a ride on equipment. If you or a contractor you’ve hired are working in or around an area with cogongrass present, avoid disturbing it with equipment and be diligent in monitoring the site for outbreaks following the job’s completion.
If you find cogongrass on your property, effectively eradicating it requires patience, persistence, and several years’ worth of herbicide applications. Currently, of the hundreds of herbicides available for purchase, only two chemistries have been proven to be very effective in destroying cogongrass, impazapyr (Arsenal, Stalker, etc.) and glyphosate (Roundup, Cornerstone, etc.).
- Imazapyr is an extremely effective non-selective, residual herbicide that controls a wide variety of weed species, including cogongrass. Just one or two applications of imazapyr can provide 18-24 months of effective cogongrass control, with follow up treatments required as needed after that. However, Imazapyr has a major downside that limits its use in many settings. Because it is a non-selective herbicide with significant soil residual activity, it cannot be used around the root zones of desirable plants. Oaks, other hardwood trees, and most landscape plants are especially sensitive to imazapyr. This herbicide is best limited to use in fields, waste/fallow areas, natural areas, and monoculture pine plantations – it is not appropriate in most residential and commercial landscapes.
- The other option, glyphosate is a non-selective herbicide with no soil residual activity. It is often a better option where severe injury or death of desirable hardwood trees and ornamental plants cannot be tolerated. However, due to its lack of residual soil activity, glyphosate applications on cogongrass patches will need to be repeated on an annual or biannual basis for up to five years for eradication of the infestation.
*Regardless of which herbicide you choose, controlling cogongrass is a multi-year affair requiring diligence and patience.
For more information on cogongrass and for specific herbicide recommendations and application rates/timing for your site, please contact your local UF/IFAS County Extension Office.
Photo by Full Earth Farm.
Yes, that’s right! We made it through the hottest part of the year and we are looking ahead to fall just around the corner! I am excited to be discussing September and what we can do to prepare for fall in the garden. As the nighttime temperatures start to cool down, we are given many more options.
For annual color plantings in September, try Ageratum, Celosia, Zinnias, and Wax Begonia to add fall color to your landscape. Bulbs will also add color, texture, and pattern to a bed. If you have some extra space, a variety of elephant ears could really accent a bed or you could always go with the classic calla, narcissus or zephyr lily. Popular vegetables to plant in North Florida in September are broccoli, carrot, cabbage, and collards. See Vegetable Gardening in Florida This is also the time of year to establish strawberry plants. Some great herbs to get started are Mexican tarragon, mint, rosemary, and basil.
Image Credit: Matthew Orwat UF/IFAS Extension Washington County
There are many things that can be done in your lawn during September. Monitoring your lawn for its health and potential insect pests is important this time of year. Common insects to scout for are fall armyworms, chinch bugs, mole crickets, and sod webworms. The last fertilizer application should be done by the middle to end of September. Make sure you choose a fertilizer with little to no phosphorus unless a soil test shows differently. To maintain a healthy lawn, avoid weed and feed products and only apply herbicides in areas with high infestations of weeds. Weed and feed products are not recommended because the timing of when to fertilize and the timing of the weed killer is not always the same. The best management practice is to use a separate treatment for weeds and when possible spot treat weeds.
If you already have bulbs in your landscape from previous growing seasons, this is the time to divide and replant those that are big. You can also add organic matter to new planting areas. Continue working on your vegetable plants and prepare them for either transplants for a fast start, or plants seeds for more variety. Throughout your landscape, it is important that plants are getting the right amount of water as we go in and out of wet and dry weather this time of year.
October will be here before we know it in just a couple of weeks. Look out for the next article to come. We will be getting into the cooler nights and more options for planting vegetables and herbs!
Growing Key Limes in the home landscape is not only a fun and unique addition, but is also delicious – any way you slice them.
The key lime, Citrus aurantifolia, originated in southeast Asia. Genetically speaking, the key lime is likely a tri-hybrid cross between the “odd ball fruits”, known as citron, pummelo and a microcitrus species, Citrus micrantha. There is little commercial key lime production nowadays in Florida, but the fruit remains a very popular landscape option.
The key lime is a small, bushy tree that makes harvest and pruning a breeze. Like most citrus, it’s self-pollinating. The key lime is also an ever-bearing fruit, so there is no real seasonal harvest. The tree could technically bloom any month of the year. There are very few varieties, as trees mostly come from true seed or air layering.
Key Lime fruit at various degrees of ripeness. Photo courtesy of Ray Bodrey, UF/IFAS Extension Gulf County.
Climate is an important factor when deciding to plant a key lime. They are sensitive to cold temperatures, especially below freezing. For the Panhandle, it’s wise to keep key lime trees as patio citrus. In other words, keep the trees in pots so that they can be moved indoors for protection during the winter months. In the ground, trees should be planted in an area where there is a significant wind block. Once a few years have passed and tree has become more mature and acclimated to the environment, they may be able to survive on their own, though it is recommended to cover the tree under sub-freezing temperatures. However, it is important to remember that sunlight is a catalyst for citrus fruit production, be sure to plant the tree in an area with full sun.
The usual suspects of citrus insect pests apply to the key lime also. Citrus leaf miner and mites are the most common culprits. Horticultural and insecticidal oils will certainly help to combat these threats. For planting, key lime is well adapted to a variety of soil conditions in Florida. Be sure to water newly planted trees every other day for the first week and then one to two times a week for the first couple of months. Water periodically after that, making sure the soil doesn’t stay completely dry for long periods. A 6-6-6 fertilizer works great for the key lime. Please follow the fertilizer schedule found in the UF/IFAS EDIS publication, “Citrus Culture in the Home Landscape” by Robert E. Rouse and Mongi Zekri: https://edis.ifas.ufl.edu/pdf/HS/HS132/HS132-11822781.pdf
A final interesting thing about the key lime is the ripening stages of the fruit. Because key limes are ever-bearers, blooms can develop at sometimes widely varying times. This causes an uneven development of fruit across the tree. Be sure to wait until the fruit turns begins to turn yellow before harvest. That’s when it’s mature to eat! Fruit can be stored for up to a week in the fridge or can be juiced and stored in the freezer for later use.
Please contact your local county Extension office for more information. Happy Gardening!
Information for this article can be found in the UF/IFAS EDIS publication, “Key Lime Growing in the Florida Home Landscape” by Jonathan H. Crane: https://edis.ifas.ufl.edu/publication/CH092
UF/IFAS Extension is an Equal Opportunity Institution.
Hot, summer months are not the time to be using most lawn herbicides.
One issue is the heat of summer. Most lawn herbicide labels include statements such as the following.
“Do not apply when temperature exceeds 90°F.” “Do not broadcast apply this product when air temperatures are above 90°F (85°F for St. Augustinegrass) unless temporary turf injury can be tolerated.”
Every year we’ll see lawns that are injured or killed because of lawn herbicides being applied when temperatures are too hot.
Summer is usually a rainy and windy time of the year. Many lawn herbicide labels include statements such as the following.
“Allow 12 hours after application before watering lawn for maximum effectives on listed weeds.” “Apply only when wind is no more than 10 mph.” “Applying this product in calm weather when rain is not predicted for the next 24 hours will help to ensure that wind or rain does not blow or wash pesticide off the treatment area.”
It is critical to read and follow the label directions and precautions for any pesticide you use. Pesticide labels, including herbicides, include the following statements.
“To the extent consistent with applicable law, the buyer assumes all risks of use, storage, or handling of this product not in accordance with label directions.” “It is a violation of Federal law to use this product in a manner inconsistent with its labeling.”
Crabgrass growing in centipedegrass lawn. Photo credit: UF/IFAS Extension
By the time summer arrives, many of the lawn weeds are mature, which means they are well established with extensive root systems. These mature, well established weeds are much more difficult to control. They are more susceptible to herbicides when they are small, young, and not well established. Also, these mature weeds have been allowed to produce countless numbers of seeds as they move into summer. Most weeds are prolific seed producers. For example, a single crabgrass plant (a common summer lawn weed) can produce 150,000 seeds.
Applying a preemergence lawn herbicide in February to help prevent summer annual weeds such as crabgrass or applying a postemergence lawn herbicide during spring while the weather is mild and before the weeds are out of control simply makes more sense than waiting until summer.
The best options now with lawn weed control involve continuing to follow good mowing practices, maybe hand removal of some weeds, and just simply waiting it out until next February and spring to worry with the use of lawn herbicides.
In the meantime, you may want to read the following UF/IFAS Extension publication on lawn weed control.
Larry Williams, UF/IFAS