Greenhouse Management Editor
Nursery Management Editor
Greenhouse Management Editor
Nursery Management Editor
Mums are a key product for many greenhouse and nursery growers in North America. While many of the tenants of mum production are well-established, there are still a variety of issues growers must navigate.
According to Nancy Rechcigl, technical services manager for ornamentals at Syngenta, mum production largely takes place outside of a controlled environment, which means the crops are susceptible to certain pest issues.
“Since much of the garden mum production is grown primarily outside, they can be prone to invasion by several insect pests such as aphids, thrips, caterpillars and occasionally some leafminers,” Rechcigl says. “Two spotted spider mites can also be a problem and can build up quietly and quickly under the high temperatures of summer.”
As far as disease issues are concerned, she says root rot, caused by Pythium spp., and fusarium wilt, caused by Fusarium oxysporum, cause the most problems for garden mums.
“High temperatures and direct sun on the container can raise soil temperatures and cause stress to the root system,” Rechcigl says. “Then periodic rain events can sometimes cause the media to become over-saturated for a period of time. This drying and wetting of the media can cause injury to the roots, allowing an entryway for these pathogens. In the northern regions, rust diseases are also of serious concern and must be prevented with a rotation of appropriate fungicides.”
There are, however, ways for growers to have successful mum crops and deal with these issues and others.
According to J.C. Chong, professor of entomology at Clemson University, the top pest issue for mums are aphids. Common types of aphids include melon aphids and green peach aphids. He says aphids are a problem for growers during the entire production cycle.
“When the plant is being stuck, fungus gnats become a huge problem there too,” Chong says. “But as soon as the plant gets to a certain size and the growing media dries up a little bit, the fungus gnats more or less disappear. And then aphids really start to pick up.”
He says whiteflies and spider mites can also be a problem during the mum production cycle, especially if mums are being produced outside.
At Clemson, Chong has performed trials with two Syngenta products: Mainspring® GNL, an IRAC Group 28 insecticide used to combat thrips, whiteflies, aphids, caterpillars and other chewing pests, and Acelepryn®, an insecticide providing season-long control of grubs, as well as several species of caterpillars.
In Chong’s studies, he and his team looked at how the products were dealing with caterpillars, particularly armyworms, which are common in South Carolina.
For Mainspring GNL and Acelepryn, Chong trialed the products as a drench and a spray to see how long the products will work. They were applied once, but at different rates.
“What we do is drench the plant, put the leaves in a dish, offer them to the armyworm larvae and see how many survive,” Chong says. “What we are seeing is that the survival rate is extremely low. From zero to 14 days, we don’t see any of them surviving at all. For 35 days after foliar applications, we see a little bit of reduction in their mortality rate, but the mortality rate is still at about 80-90%.”
According to Chong, both sprays and drenches of Mainspring GNL and Acelepryn work well for controlling worms across all rates.
“You can really expect one foliar application to give you 30 days of protection and one drench probably giving you 39 days of protection,” Chong says.
For growers looking to decide what product is right for them, Chong recommends matching the label for what the exact needs are. Acelepryn has a narrower pest spectrum than Mainspring GNL, but for controlling worms, the two products work similarly. If growers need protection and control against a broader spectrum of pests (aphids, thrips, leafminers, etc.), then Mainspring GNL is your tool, says Rechcigl.
For controlling worms, both products work well, Chong says.
As noted, fusarium is a leading disease issue for mums. According to Dave Norman, an associate professor of plant pathology as the University of Florida, fusarium is a fungus common in the environment. It often gets into production during the beginning stages. During mum production, it can cause root damage, but is most harmful toward the crown of the plant.
“It primarily moves in a nursery via contaminated soil, by workers or by plants that have been brought in from an infected area,” Norman says. “It easily moves around a growing environment.” He adds that it can be especially harmful when plants are bigger or near the end of the growing cycle, and is more harmful when the weather is hot and/or humid.
“When you get into the southern states, it’s more severe, especially in the summer months when you’re getting your plants ready to sell,” Norman says.
He recommends not irrigating too late in the day to avoid the plants being wet overnight and using benches when possible to keep plants off the ground.
Some symptoms of fusarium are a dark grey stem at the soil line in young plants, crown rot and root discoloration. Younger plants, however, sometimes don’t show symptoms until they have become much larger. Combatting fusarium requires rigorous treatment with the right products, Norman says. To treat fusarium, he says it’s best to use FRAC groups 3, 7 and 11. One product that combines FRAC Groups 7 + 11 is Mural® fungicide from Syngenta. Mural can be used as a drench or a spray for effective disease control.
When a grower thinks they have a fusarium outbreak, Norman says to act quickly to try and limit the spread of spores and to at least consider sending your plants to a lab to be tested.
“It’s a very aggressive fungus for mums,” Norman says. “Some of the most popular and unique colors you come across are very sensitive to fusarium. This has to be taken seriously.”
With mum production, Rechcigl says to start by thinking about rooting.
“Remember that success is all about having healthy roots,” she says. “Before placing pots out in the field, make sure the field is level with good drainage and that any low areas are fixed so standing water doesn’t accumulate. Keep plants evenly moist. If you are using drip tape to apply irrigation, look at the wetting pattern over time so you get proper wetting across all pots in all areas of the field.”
Scouting weekly for pests is vital, as is being prepared for any problems that could pop up. “While symptoms of fusarium wilt are typically seen in August, the initial infection began several weeks earlier,” says Rechcigl. “Protecting the roots in July is critical.”
As a resource for growers, Syngenta built an agronomic program for mum production that offers timing and treatment recommendations for the most common insect and disease targets. It’s available here.
According to Mark A. Smith, technical service lead for Syngenta Flowers, one other market change is a shift toward unrooted cuttings vs. rooted cuttings. The cuttings are coming in around May/June if they are unrooted, with growers finishing the plants in the fall. Smith says the rise of larger growers having a propagation team in place at their facilities is a major reason why unrooted cuttings have grown in popularity.
“Mums are one of the easiest crops to root, so why not save on the input cost and do that work yourself?” Smith says. “It’s a lower cost to start with unrooted, too.” The only difference is the length of the growing cycle. Smith says if a grower wants to produce mums from unrooted cuttings vs. rooted cuttings, it’s wise to start two to three weeks earlier. Otherwise, the process — and the different issues growers can face during production – is largely the same.
“One key thing to remember is that feeding and watering mums will absolutely drive growth,” Smith says. “Mums are best on a constant liquid feed program. They need to be on a high volume of nitrogen, but they need to be fed on a regular basis.”
©2020 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration status and proper use. Acelepryn®, Mainspring®, Mural®, and the Syngenta logo are trademarks of a Syngenta Group Company. Syngenta Customer Center: 1-866-SYNGENT(A) (796-4368).
Although less common than traditional ornamental insect pests like whiteflies and thrips, the European pepper moth and red-headed flea beetle are two pests continuing to gain notoriety across the country. While both pests have their signature activity, they share one thing in common: plant damage. J.C. Chong, professor of entomology at Clemson University and Nancy Rechcigl, technical services manager of ornamentals at Syngenta, share ways growers can control, combat and contain these pests.
While the European pepper moth originated in Europe, Rechcigl says their appearance in the U.S. has grown over the last five years. In 2014, the moth was a confined “quarantine pest” in a small area in Southern California, but now, she says they are being seen in states in the Northeast like New Jersey, New York, Connecticut and Pennsylvania, along with Southeastern states including Florida and in Texas. Chong says he’s also seen “a big jump” of moths in North and South Carolina.
Rechcigl recalls the first observance of European pepper moths in herbaceous crops, annuals, perennials and poinsettia production, but they are quickly claiming other crops. “We are starting to see activity in woody ornamentals as well,” she says.Chong believes the moths seek herbaceous crops and woody ornamentals because it is easier for them to feed on the plant tissue.
As for the red-headed flea beetle, Rechcigl says there has also been a surge of them in outdoor ornamental production. Like the pepper moth, they feed on herbaceous and woody ornamentals, and the injury they can cause in a short period of time can leave plants unsalable, she says.
Scouting at the base of the plant is critical for finding this pest.” — NANCY RECHCIGL, technical field manager of Turf and Ornamentals at Syngenta
The damage both pests can do differ from the destruction caused by whiteflies and aphids. Instead of leaf yellowing and distortion as the result of the latter sucking pests, the pepper moths and flea beetles chew.
“The European pepper moth larvae chew and bore their way into the base of the plant,” Rechcigl says. “This can cause the plant to appear wilted and can be mistaken for a root issue. Unfortunately, if too much of the lower stem is damaged, this can result in the death of the plant. Flea beetles feed on the upper layers of leaf tissue, leaving the plant with a skeletonized appearance. The more injury present can significantly reduce the value and salability of your crop. When injury levels approach 40% or higher, the plant is often unsalable.”
Like many insect pests, scouting and preventative applications are recommended. According to Rechcigl, European pepper moths lay their eggs in the upper canopy of the plant, but after hatching, the larvae drop to the soil and begin feeding on the base.
“Scouting at the base of the plant is critical for finding this pest,” she says. “They are rather small and can almost be mistaken for fungus gnat larvae because they have a dark head capsule and are just slightly bigger in size. The larvae will produce a light webbing which provides them some protection from predators. So when scouting, look for light webbing at the base of the plant at the soil line.”
Flea beetles, however, eat the upper layers of foliage and leave the lower epidermis intact, which gives a skeletonized appearance. Rechcigl says it’s harder to scout them due to their swift movement if the foliage is disturbed, and because of this, she says the feeding injury will most likely be seen before the actual pest. Chong says the multitude of these pests make them harder to control.
“These pests are quite destructive if left unchecked, so it is important to begin control treatments as soon as indications of their presence are observed,” Rechcigl adds.
To assist growers, Syngenta offers Mainspring® GNL, Acelepryn®, Flagship® 25 WG and Scimitar® GC, insecticides that guard against many pests and provides tools for integrated pest management plans.
“For the European pepper moth, both Mainspring GNL and Acelepryn can be used to control this pest … [they] should be applied as a heavy spray over the top of the plant so the base of the plant and stem is wet at the soil line,” Rechcigl says.
Recent trials have shown Mainspring GNL and Acelepryn are effective on the European pepper moth for seven weeks.
In Chong’s 2019 trial for European pepper moths, he observed the efficacy of Mainspring GNL and Acelepryn against the pests in the greenhouse.
“From treatment until 42 days, plants that were treated with Mainspring and Acelepryn did not see any foliar damage at all,” he says. “For water-treated plants, we saw about 33% of the plants showing damage. This tells me that Acelepryn or Mainspring can wipe out the European pepper moth caterpillars.”
For flea beetles, Rechigl recommends Flagship 25 WG, Scimitar GC, Mainspring GNL or Acelepryn. During his flea beetle research, Chong sprayed plants with Acelepryn and Mainspring GNL three times at a 14-day interval.
“To give an example, at 42 days after the first treatment, 40.8% of the terminals of plants sprayed with only water suffered some level of damage,” he says. “But the damage was reduced to 21.7% and 25% for Mainspring GNL- and Acelepryn-treated plants. So, Mainspring GNL and Acelepryn can certainly reduce, but not completely eliminate foliage damage [because] there are just so many of the hungry beetles out there and damage can accumulate even if one beetle takes just a little bite.”
Trials on the flea beetles have shown three applications of Mainspring GNL and Acelepryn on a 14-day interval keeps the plant injury levels under 20% to 25% for a seven-week period.
©2020 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration status and proper use. Scimitar GC is a Restricted Use Pesticide. Acelepryn®, Flagship®, Mainspring®, Scimitar® and the Syngenta logo are trademarks of a Syngenta Group Company. Syngenta Customer Center: 1-866-SYNGENT(A) (796-4368).
With the advent of new fungicides and pesticides available, it’s important for growers to take note of the options available to them. IRAC/FRAC (Insecticide/Fungicide Resistance Action Committees) provide growers with relevant pest control information and advice. With proper product rotation and new MOAs (mode of action), growers can keep pests and diseases at bay.
Daniel Gilrein, extension entomologist with Cornell Cooperative Extension of Suffolk County, is an expert in this field and often advises growers concerning the use of insecticides and miticides. Gilrein says the IRAC classifications are very helpful, particularly when targeting some pests and situations where there is a significant risk of resistance development, such as in greenhouse and nursery production of ornamentals.
Gilrein says there are a few things growers need to keep in mind when it comes to properly rotating insecticides. After the pest problem is identified where treatment is deemed necessary, he lists out a plan based on the following factors:
When pests develop a resistance, managing them becomes an extremely difficult task and may lead growers to have to discard a portion, or all, of their crops. “They must rotate chemistries and be proactive about managing resistance because some pests are notorious for developing insecticide- or miticide-resistant populations. Additionally, the population at hand may already have resistance to some materials,” Gilrein says.
“Rotating among different modes of action can reduce the risk of promoting resistance or maintaining resistance in a population that already has it. It is especially important for propagators to be aware of the issue, so resistant pests are not conveyed with plant material,” he says. “Also, we want to make sure insecticides and miticides will work when we need them, and they continue to be available and useful for a very long time; thinking of susceptibility as a kind of ‘natural resource’ we want to conserve.”
Enter diamide insecticides in IRAC Group 28, which differ from traditional chemistries. Nancy Rechcigl, technical services manager for ornamentals at Syngenta, shares why using diamides is a good option for growers.
“The active ingredients in this group selectively activate the ryanodine receptor in the insects’ muscles, causing the release of calcium ions,” Rechcigl says. “This results in paralysis and rapid inhibition of feeding and other key physiological functions. Insect feeding is typically stopped after initial ingestion, and insect mortality is observed within 2-7 days, depending on the pest.”
“Many insecticides in other IRAC groups affect different aspects of the pest’s nervous system, the diamides target a different site, making them a good rotational tool. This class of chemistry has also shown to be compatible with the use of beneficial insects and mites, which makes them an ideal partner in integrated pest management programs,” she says. “When plants are treated with a diamide and challenged with insect pressure, the plants are protected and the pests are not able to establish in the crop.”
For successful integrated pest management programs, growers should focus on preventive applications rather than curative, which is especially necessary when using biological controls, according to Gilrein. Managing the problem early is key, because gaining control later may be much more difficult, due to things like high pest populations, dense plant canopies and plants arranged or spread out that makes insecticide coverage difficult — and may require more material to get rid of the insects.
Rechcigl notes diamides can be used in curative applications for pests such as worms and leafminers, but preventive applications (when the pests are first observed) are best for controlling whiteflies, thrips and mealybugs.
“In addition to use as foliar sprays, some diamide insecticides have systemic activity when applied to soil, media or bark, and relatively few other insecticides have such systemic uses,” says Gilrein.
Mainspring® GNL and Acelepryn® insecticides from Syngenta are two diamide chemistries with systemic activity that act as shields to protect plants from a wide range of insects.
“While the mode of action of how they work is similar, the different active ingredients within the diamide class of chemistry differ somewhat in their pest spectrum and in their systemicity,” says Rechcigl. “While all diamides have translaminar activity, only cyantraniliprole (Mainspring GNL) and chlorantraniliprole (Acelepryn) can be applied as a foliar or bark spray or as a drench for long, systemic protection.”
Margery L. Daughtrey, senior extension associate at Long Island Horticultural Research & Extension Center at Cornell University, shares why it’s important to properly rotate fungicides. She says diseases with rapid epidemic development and prolific pathogen sporulation, such as Botrytis blight, downy mildews and powdery mildews, are the ones where it is most important to practice fungicide rotation — and is critically important for crops being cultivated in greenhouses.
She notes key resources are the information on the product label (where the FRAC group is always given) and the FRAC website itself, which updates listings every year.
“The main danger is that you think you are rotating properly when in reality you’ve followed one fungicide application with another one from the same FRAC group — which means they will have the same mode of action, even though the product name and the fungicide’s common name might sound quite different,” Daughtrey says. “Strobilurin fungicides, for example, they are all in FRAC Group 11, so there is no point to treating twice with Heritage and then ‘rotating’ to treat twice with Compass. You’ll be exposing the fungus population to the same weapon by a different name, and you will be encouraging strobilurin resistance in the fungus population.”
With the help of 11+7 fungicides, like Mural® from Syngenta, growers can be sure they are using an effective management method.
The combination of two highly effective and broad-spectrum fungicide modes of action — an SDHI (succinate-dehydrogenase inhibitor) fungicide paired with a strobilurin — will slow resistance development to a pathogen that happens to be susceptible to both, she says.
“Using contact action materials at low or no danger of resistance development during periods when the environment is not highly conducive to disease, or alternating them with 11+7 materials, is a good strategy.” — MARGERY L. DAUGHTREY, senior extension associate at Long Island Horticultural Research & Extension Center at Cornell University
“An 11+7 material will help you to cope with leaf spots, powdery mildews, downy mildews and rusts,” she says. “And you are likely to be getting some systemic action against the pathogens.”
Daughtrey notes growers shouldn’t rotate an 11+7 or an 11+3 fungicide with an 11 fungicide. This is due in part from the perspective of the tiny fungus growers want to manage. It will see continuous 11s, and growers will thus increase the selection pressure, so the strobilurin component will become ineffective sooner, she says.
“Using contact action materials at low or no danger of resistance development during periods when the environment is not highly conducive to disease, or alternating them with 11+7 materials, is a good strategy,” she says, “Learn which fungicides work best against the problems your crops are subject to, and deploy them strategically, keeping in mind the need for thoughtful fungicide rotation.”
The key attribute that makes Mural an ideal choice for growers is due in part to its translaminar and systemic activity, but also because it is xylem mobile.
“When applied as a drench for protection against root and crown rots, Mural will move upward into the plant canopy to provide protection against certain foliar diseases, such as rusts and some powdery mildews,” says Rechcigl. “It is very useful for protecting daylilies or ornamental grass crops against rust, with one drench application providing six to eight weeks of protection.”
Mural also provides good control/suppression of Pythium spp. and offers plant health benefits. Increased root density has been routinely observed with drench applications using 2-3 ounces and foliar sprays applied at rates of 4-5 ounces.
When it comes to proper rotation, Rechcigl says a robust resistance management program should include a rotation of products from at least three to four different classes of chemistry (three to four different IRAC and FRAC Codes) for each pest or disease target. For fungicides, growers should make one or two applications of the same product (if the label allows) before rotating to a different class of chemistry. Insecticide/miticide applications should target the life cycle of the pest.
“Being good stewards and preventing resistance from developing allows the grower to have more options and tools in their management toolbox. Research and development activities for the discovery of new active ingredients with new and different modes of action takes time, often 10 to 12 years, and requires a significant investment in time and resources,” Rechcigl says.
Syngenta has developed several agronomic programs with built-in resistance management strategies. They are available for download here.
©2020 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration status and proper use. Acelepryn®, GreenCast®, Mainspring®, Mural®, and the Syngenta logo are trademarks of a Syngenta Group Company. Syngenta Customer Center: 1-866-SYNGENT(A) (796-4368).
The Horticultural Industries Leadership Awards (HILA), sponsored by Syngenta, is the only North American awards program to honor leaders from the greenhouse and nursery industries. Six award winners will be honored in these industry sectors in North America.
HILA recipients have made significant contributions to the horticulture industry, such as furthering its development with their innovation and expertise, excelling in environmental stewardship, enhancing the lives of employees, customers, communities and the industry at large with their charitable giving, and/or otherwise making a positive impact on the industry.
Is there a nursery or greenhouse grower you think should join the Horticultural Industries Leadership Awards Class of 2021? Email the following information to HILA@gie.net to nominate them today!