by Daniel J. Leonard | May 13, 2020
It’s been a challenging spring in this guy’s garden! Despite getting the normal early start required for successful gardening in Florida, I’ve been affected by Bacterial Leaf Spot stunting my tomatoes, cutworms that reduced my watermelon plantings by half, and an eternal test of my patience in the form of a dog that seems to think my raised beds are merely a shortcut to a destination further out in the yard. My latest adversary is the most potentially destructive yet, an outbreak of Southern Armyworm (Spodoptera eridania).
Early Southern Armyworm damage on Okra seedlings. Photo courtesy of the author.
Unlike some serious garden pests that wait until the heat of summer to emerge, Southern Armyworms begin appearing in spring gardens around the end of April. Adult moths can survive mildly cold weather and venture into the Panhandle as soon as warmer spring weather arrives. Once the adult moths arrive, egg masses are then laid on the undersides of leaves and hatch in a little under a week. Once loosed upon the world, Southern Armyworm larvae (caterpillars) become indiscriminate, voracious feeders and congregate in extremely large numbers, allowing them to destroy small, developing garden vegetable plants in a manner of days. Young larvae feed on the undersides of leaves and leave little but a skeleton. As larvae grow larger, they become solitary and begin to bore into fruit. Once they’ve eaten the good stuff (leaves and fruit), large larvae turn to branches and even plant stems!
Southern Armyworm larvae feeding on Okra leaves. Photo courtesy of the author.
The good news for gardeners is that Southern Armyworm, and most other caterpillar pests, are easily controlled if outbreaks are caught early. Scouting is critical for early detection and good control. Armyworm damage generally appears from above as brownish-gray sections of affected leaves with a yellowish ring surrounding these sections, this ring indicates the current feeding zone. Affected areas will appear transparent and “lacy” due to the skeletonizing effects of larval feeding. If you see leaves that look “off” in the manner just described, check underneath for the presence of a horde of tiny greenish worms.
If found in this early stage, an application of Bacillus thuringiensis (Bt), a biological pesticide utilizing a bacterium destructive to caterpillars, is extremely effective. Bt has to be ingested by caterpillars with leaf tissue to work; thorough coverage of leaf surfaces is critical for maximum control. I generally follow up with a sequential application of Bt a day later to ensure that I achieved good coverage of the plant surfaces and, therefore, good control. Unfortunately, Bt is much less effective on older larvae. Infestations not caught early require harsher chemistries like carbamates, pyrethroids and organophosphates for adequate control.
Don’t let armyworms or other caterpillar pests destroy your garden, get out there daily and scout! You have a short window for easy caterpillar control with a harmless to people, natural product, Bt. Don’t waste it!
For more information about Southern Armyworm, other caterpillar pests, Bt, or any other horticultural topic, please consult your local UF/IFAS Extension Agent. Happy Gardening!
by Daniel J. Leonard | Apr 29, 2020
‘Multipik’ fruit. Photo courtesy the author.
Never one to be satisfied growing “standard” vegetable varieties, last year I decided to peruse various seed sources in search of a superior yellow summer squash selection. Plain ‘Yellow Crookneck’ just wasn’t doing it for me anymore. After doing a little research and consulting a friend who works for Johnny’s Selected Seeds, I settled on a straightneck variety called ‘Multipik’.
Developed in the 1980’s by Harris Seed and now sold by many seed purveyors, ‘Multipik’ enjoyed immediate popularity with commercial squash growers due to its many outstanding qualities but curiously, is just making inroads with the home garden market. Even as it is set to celebrate its 30th anniversary next year, two years of personal experience with ‘Multipik’ verify several important characteristics making it a superior choice to many other traditional summer squash varieties: earliness/heavy yields and a precocious gene.
Newly developing ‘Multipik’ fruit. 4 weeks after planting. Photo courtesy the author.
The longer I garden, the more I’m convinced that earliness to maturity is directly related to yield potential in home gardens, especially in the Panhandle. Lots of varieties have high yield potential but that potential is often at least partially wasted here due to the length of time from seed to harvest. Ideally, you could plant, grow a crop and be done by mid-late June, before intense heat, humidity and all the wonderful garden pests and diseases arrive to destroy spring gardens. Maturing just 50 days from planting, ‘Multipik’ beats that deadline (when planted on time in late March) and yields heavily for at least a month before succumbing to the harsh Panhandle summer. Many traditional summer squash varieties, including ‘Yellow Crookneck’ mature 8-14 days later. While 8-14 days doesn’t sound like much, it can mean a major yield difference when factoring in the almost certain late season pests, diseases, and adverse weather conditions.
The next major advantage ‘Multipik’ offers is a precocious gene, meaning that it will mask symptoms and maintain its yellow color if infected with either Watermelon Mosaic Virus (WMV) or Cucumber Mosaic Virus (CMV), two destructive pathogens commonly affecting squash by discoloring fruit and reducing yield. This trait is critical to commercial growers because yellow squash that isn’t yellow isn’t marketable and is important to home gardeners too as a means to eke out higher yields under virus pressure. While the precocious gene isn’t a cure for either virus, it can help hold them at bay while you harvest! Another quirk caused by the precocious gene is the all-yellow appearance of the fruit, from the peduncle (the stalk holding the fruit to the plant) to the apex! From one end of the fruit to the other, Multipik ensures that when you plant yellow squash, you harvest yellow squash.
‘Multipik’ just days from harvest. Photo courtesy the author.
Whether you are trying to avoid yield loss from late season insect and disease pressure plaguing your traditional squash plantings or just want to try something a little different, I highly recommend planting ‘Multipik’ Squash. This early, disease-resistant cultivar with delicious medium sized, light yellow fruit is sure to be a hit in both in the garden and on the table. As always, if you have any questions about vegetable gardening or any other horticultural topic, give your local UF/IFAS County Extension Office a call! Happy gardening!
by Larry Williams | Apr 29, 2020
In times like these, it seems that our own perceived “problems” pale in comparison to the “big picture.” In my day-to-day work, I have the opportunity to help people solve problems with their landscapes, lawns and gardens. I enjoy the problem solving part of my job as an extension agent.
Winter annual weeds in lawn in early spring. Photo credit: Larry Williams
You’d be surprised how upset some people can be about a few weeds, a dying petunia or a tomato with a crack in it. They’ll let small things like this upset their entire world. It’s as if they think we live in a perfect world when it comes to expectations for the plants in their own landscape.
It has become apparent to me that too many people spend too much time letting too many small things bother them too much.
When my twin sister, Linda, and I were growing up in a small town in middle Georgia, an elderly couple (Mr. and Mrs. Hunt) would crack pecans and give the shelled halves to us to eat. They’d hand the shelled pecans to us over the fence that separated our yards. At five or six years old this was a treat for my sister and me.
I remember their landscape. I remember Mrs. Hunt sweeping their dirt driveway lined with coconut sized rocks. She used handmade brooms. I remember their pink flowering dogwoods in spring. I remember their old-fashioned yellow and orange daylilies during summer. I remember the fascination of seeing red spider lilies seemingly come from nowhere in the fall underneath deciduous trees as they displayed their autumn colors. I remember Mrs. Hunt letting me smell a flower from a sweetshrub plant, which reminded me of sweet apples. The deep red blooms and dark green leaves of this shrub complemented the white wooden wall on the east side of their home.
Mulberry tree with fruit. Photo credit: Larry Williams
I remember climbing a large mulberry tree in their backyard and picking and eating the berries. I remember watching Mr. Hunt prune grapevines growing on an overhead trellis. I remember learning about the history of a ginkgo tree planted just outside a chicken pin in their side yard. I remember watching hummingbirds flying in and out of the reddish orange funnel-shaped blooms of a large trumpet vine growing on an old metal frame of a water tank.
I don’t remember the weeds, even though I know there must have been weeds in the Hunt’s landscape. I know there was the occasional pecan that didn’t fill out or that was worm infested. And I’m sure an occasional plant had to be replaced. But these are not the things that made lasting impressions for me.
The big picture is not the weeds, the dying petunia plant or the pecan with a worm in it. Sure you will have weeds in your yard and certain plants that don’t survive. Just don’t let these things become the source of worry. In my opinion, a landscape should be a source of pleasure, a place to learn and a place to pass along lasting memories. Besides, with all the things there are to worry about in this world (as recent days have revealed), why let your own backyard be one of them?
by Sheila Dunning | Apr 23, 2020
Members of the Phyllophaga genus are found throughout Florida and most of North America. One of them is the May/June beetle. Adults are most active during the rainy season. So in parts of the country where the wetter months are May or June, the common name of this insect makes common sense. But, when an area experiences extra rain earlier in the spring, the May/June beetle may emerge from the ground in March or April. That is what has happened in the western Panhandle this spring. May/June beetles have been leaving the soil and flying to the lights of people’s homes.
The life cycle of these beetles varies from one to four years. Eggs are laid in soil each spring by females. In 3 to 4 weeks, small grubs (larvae) hatch from eggs and develop through three stages (instars), with the first two stages lasting about 3 weeks. The larvae will move closer to the surface and back deeper in the soil as the soil temperature changes. While close to the surface, larvae feed on grass roots about one inch below the soil surface. Damaged grass turns brown and increases in size over time. Heavy infested turf feels spongy and moves when walked upon. The last larval stage remains in the soil from the fall through spring. The cool soil temperatures drive the larvae deeper in the soil where they remain relatively inactive. Typically, on the third year, white grubs pupate 3 to 6 inches deep in the soil and emerge as adults.
Larvae, called grubs, vary in length from ¾ to 1 ¾ inches depending on the stages. Grubs are white with a C-shaped body with a brown head and three pairs of legs near the head. Adults have ½ to 1 inch long, shiny bodies that are dark yellow to brownish-red in color. Adults do feed on the foliage of several species of ornamental plants, but the damage is typically only aesthetic; not causing long-term harm.
Monitoring of and managing emerging adults can help with deciding on the need for insecticide control for the grubs. To catch and remove adult beetles, place white buckets containing soapy water near plants that have chew marks or areas with lights at night. Leave it overnight. The beetles can easily be disposed of the next day. If there are more than 12 in the bucket be prepared to monitor the lawn for grubs. Extra rain or frequent irrigation during the adult flight time may attract more egg-laying females.
To inspect for grubs, turn over sod to a depth of at least two-inches. If there are an average of three or more per square foot, an insecticide treatment may be needed. To confirm that they are May/June beetles inspect the darkened rear of the grub. Locate the anal slit. It should be Y-shaped with two rows of parallel bristles that point toward each other. This is referred to as the raster pattern. All grub species can be identified using their unique “butt” features.
The most effective time to control this pest is summer or early fall when the larvae are small. Remove as much thatch as possible before applying an insecticide. Spot treat the off-colored area plus the surrounding 10 feet with products containing imidacloprid or halofenozide in early summer. Follow up in the fall with insecticides such as trichlorfon, bifenthrin or carbaryl if grubs persist.
by Larry Williams | Apr 23, 2020
One of the things to do while stuck at home due to COVID-19 restrictions, is to look for caterpillars and butterflies in your landscape. I’ve noticed giant swallowtail butterflies (Papilio cresphontes) a little early this year. The giant swallowtail is one of the largest and most beautiful butterflies in our area. Its larval stage is known as the orangedog caterpillar. This unusual name comes from the fact that it feeds on young foliage of citrus trees.
Orangedog caterpillar. Photo credit: Donald Hall, University of Florida
The orangedog caterpillar is mostly brown with some white blotches, resembling bird droppings more than a caterpillar. When disturbed, it may try to scare you off by extruding two orange horns that produce a pungent odor hard to wash off.
I’ve had some minor feeding on citrus trees in my landscape from orangedog caterpillars. But I tolerate them. I’m not growing the citrus to sell. Sure the caterpillars eat a few leaves but my citrus trees have thousands of leaves. New leaves eventually replace the eaten ones. I leave the caterpillars alone. They eat a few leaves, develop into chrysalises and then emerge as beautiful giant swallowtail butterflies. The whole experience is a great life lesson for my two teenagers. And, we get to enjoy beautiful giant swallowtail butterflies flying around in our landscape and still get plenty of fruit from the citrus trees. It is a win, win, win.
In some cases, the caterpillars can cause widespread defoliation of citrus. A few orangedog caterpillars can defoliate small, potted citrus trees. Where you cannot tolerate their feeding habits, remove them from the plant. But consider relocating the caterpillars to another area. In addition to citrus, the orangedog caterpillars will use the herb fennel (Foeniculum vulgare) and rue (Ruta graveolens) as a food source. Some butterfly gardens plant citrus trees to provide food for orangedog caterpillars so that they will have giant swallowtail butterflies. So you could plan ahead and grow some fennel, rue or find a butterfly garden in your area for the purpose of relocating the larvae.
Yellow giant swallowtail butterfly on pink garden phlox flowers. Photo credit: Larry Williams
The adult butterflies feed on nectar from many flowers, including azalea, bougainvillea, Japanese honeysuckle, goldenrod, dame’s rocket, bouncing Bet and swamp milkweed. Some plants in this list might be invasive.
Keep in mind that mature citrus trees can easily withstand the loss of a few leaves. If you find and allow a few orangedog caterpillars to feed on a few leaves of a mature citrus tree in your landscape, you and your neighbors might get to enjoy the spectacular giant swallowtail butterfly.
More information on the giant swallowtail butterfly is available online at http://edis.ifas.ufl.edu/in134.
by Larry Williams | Apr 15, 2020
Did you know that the first virus discovered was in plants, not in humans? As early as 1857, tobacco farmers in the Netherlands recognized a new disease of tobacco. It wasn’t called a virus at the time as the causal agent was unknown. In 1886, Adolph Mayer, a German agricultural chemist, determined that the “tobacco mosaic” disease could be transmitted to healthy plants by rubbing them with infected leaf sap.
Tomato leaf with tobacco mosaic virus. Photo credit: UF Plant Pathology Department
When taking a plant pathology course in college, it amazed me that viral organisms were ever discovered. They are extremely small. So small that it was not until the development of the electron microscope in the late 1930s that scientists were able to see the structure of the tobacco mosaic virus. Viruses are 20 – 250 nanometers in diameter, about 100 times smaller than bacteria.
The discovery of fungi and bacteria came before the discovery of viruses as the cause for plant diseases. In most cases, we have many chemical options for control of fungal and bacterial diseases in plants. But there are few to no chemical options to control viral organisms in plants. By the nature of how a virus operates in a plant cell, chemical control results in death of the host cell, surrounding tissue and possibly the whole plant.
Control of viruses in plants involves eliminating the source of the virus such as nearby weeds, control of insect vectors that transmit the disease such as aphids and thrips and use of resistant plants.
Historically, plant diseases have caused major impacts on humans. In 1845, the Potato Famine in Ireland was caused by the fungus Phytophthora infestans. This disease was responsible for the death of more than 1 million people as it devastated the production of the potato as a major food source at the time and is credited for the beginning of plant pathology as a science. Cryphonectria parasitica, an introduced fungus, essentially wiped out the American chestnut as the dominant tree in the eastern U.S. forests during the early 1900s. The excellent wood was used to build homes and the nutritious nuts were eaten by humans and fed to livestock. Currently, UF/IFAS plant pathologists are working to solve Citrus Greening, a bacterial disease that has severely damaged the citrus industry and has the potential to completely eliminate citrus production in Florida.
If it were not for the land-grant university system, of which Extension Agents are a part, there would be few to no plant pathologists in the United States. It is these land-grant universities, like the University of Florida and others, that provide plant pathology courses, training, research, development and ultimately that graduate with degrees those who go on to careers in the field of plant pathology, discovering new diseases and developing controls for these diseases.
