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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.

Solving pest issues with the right products

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.

How to deal with fusarium

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.”

more helpful tips

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.

Rooted cuttings

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.

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).

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!

• Person nominating
• Email/phone number of person nominating
• Company of person nominating
Nominee name
• Nominee email
• Nominee phone number
• Nominee company name
• In your own words, please explain in detail why you think this person deserves to win a HILA.

Nick Collins
Publisher
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Kate Spirgen
Greenhouse Management Editor
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Kelli Rodda
Nursery Management Editor
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