Top 9 Pest Reports In The Past Two Years

Several pest outbreaks took place across the U.S. over the past two years. Here are the top 9 pest-related stories you should know about:

Emerald ash borer free image1. Researchers Tracking Emerald Ash Borer In White Fringetree

Advertisement

A recent report from Don Cipollini, Ph.D. and plant physiology professor at Wright State University in Dayton, Ohio, documents the first confirmed cases of emerald ash borer in white fringetree in its completed life cycle.

“Four of 20 ornamentally planted trees in the Dayton-Springfield area that I have examined so far were infested based on obvious external symptoms,” Cipollini says. “I investigated one of them further and it yielded confirmed larvae and an adult emerald ash borer. Infested trees were showing signs of dieback.”

Ash trees can be protected with trunk injections and root drenches, Cipollini says. White fringetrees should be able to be protected in the same way, but their flowers attract pollinators and the fruits are eaten by wildlife, so non-systemic bark sprays may be the best strategy.

Top Articles
Why This Hydrangea From Green Fuse Botanicals Is a Gamechanger (Video)

“In some ways, it is perhaps not surprising that at least a few emerald ash borer were able to colonize and develop on this species,” says Deb McCullough, a professor in the Department of Entomology at Michigan State University. “In studies we conducted in past years, we evaluated the ability of adults to feed on leaves of privet and Japanese tree lilac, which are also in the Oleaceae family. Adults could definitely feed on privet leaves and larvae would try to feed on privet phloem.  However, the larvae always died before they could complete their development on privet,” she says.

“We had a relatively severe regional drought in 2012, so it appears that the fringetree (the original one anyway) might have been colonized that summer,” McCullough notes. “If a few larvae were able to feed on the phloem, they would further stress the tree, potentially attracting more egg-laying females in 2013 and 2014.”

McCullough suggests that garden center retailers might want to contact a regulatory official, either from the Ohio Department of Agriculture or at USDA’s Animal Health and Plant Inspection Service. “They may be developing new regulations to apply to fringe trees in nurseries located in areas where emerald ash borer is established.

“People in areas where emerald ash borer is present will probably want to keep an eye on white fringetree in their landscapes. We know EAB will preferentially colonize stressed host trees, so keeping the fringetrees healthy, irrigated, etc. can’t hurt.”

Vibernum Leaf Beetle

2. Viburnum Leaf Beetle Is A Pest To Watch For 

Garden center retailers are expected to be knowledgeable not just about the plants they are selling, but how to keep them healthy. This means getting familiar with pests that may threaten the health of these plants. Here’s a look at one such pest, the viburnum leaf beetle.

Where it’s found: New York/New Jersey

Why it’s a problem: The viburnum leaf beetle only attacks species of viburnum. Susceptibility among different species is highly variable, however. Cornell University’s viburnum leaf beetle citizen science website has a complete list of susceptibility ranges, but the most susceptible species are shown in the box below. Plants in the shade are generally more susceptible to attack that those of the same species in the sun.

Pest Facts:

● The beetle has just one generation per year. Eggs hatch in mid-late spring, producing larvae that damage the plants over several weeks.

● The larvae pupate in the soil, yielding adults that emerge in early summer and feed on the leaves until late summer.

What You And Your Customers Need To Know:

● If a retail garden center customer purchases one of the highly susceptible varieties, they will likely need to perennially manage viburnum leaf beetle, if it exists in their area. Resistant varieties will be largely carefree.

● There are a range of management options, which vary with respect to efficacy, cost and impact on non-target organisms. The most effective management practice is systemic application of imidacloprid, applied to the soil. This chemical will protect the entire plant for two growing seasons if properly applied and allowed time to be taken up by the plant distributed throughout its foliage.

● For homeowners who wish to use less persistent insecticides, applications of insecticidal soap offer adequate control of feeding by small larvae, but application must be thorough (reaching the undersides of leaves where small larvae feed), and may require re-application. Larger larvae and adults are not controlled by insecticidal soap. Check the label of insecticides to make sure a particular product is labeled for use against viburnum leaf beetle in your area and the particular setting.

● For those not wishing to use insecticides at all, removal of viburnum shoots infested with eggs can significantly reduce damage from larvae if done before eggs hatch. Time of egg hatch varies with location and the particular season, but typically occurs in mid to late spring. To be safe, the infested shoots should be removed in late winter; not only will this allow removal of egg masses before the eggs hatch, it is much easier to spot the egg masses before leafing out occurs.

● Larvae tend to cause more damage than adults because they occur in larger numbers because of the clustering of eggs, their feeding damage is often undetected early on and they feed on the plants at a more vulnerable stage.

Information courtesy of Paul Weston, previously with Cornell University and now at the Charles Sturt University School of Agricultural and Wine Sciences in Australia

 

Red Headed Flea Beetle

3. Red-Headed Flea Beetle Targeting Mid-Atlantic Plants

Garden center retailers are expected to be knowledgeable not just about the plants they are selling, but how to keep them healthy. This means getting familiar with pests that may threaten the health of these plants. Here’s a look at the red-headed flea beetle, which is becoming a major concern in the Mid-Atlantic region.

Where it’s found: As far north as Connecticut, as far west as Michigan and as far south as Mississippi

Why it’s a problem: The red-headed flea beetle has become more common and widespread in nurseries and greenhouses since 2008. The initial appearance was of little concern and thought to be a nuisance or sporadic feeder on ornamental plants.

Currently, this insect is causing substantial damage to a large number of different plants in the mid-Atlantic. The insect seems to prefer feeding on new leaves as they begin to grow, but will also feed on older leaves. They chew holes either through the entire leaf or just on one side of a leaf, which dries out, thus turning brown. This scarring of the leaves often renders them unsalable.

Pest facts: Some of the most common hosts include itea, salvia, sedum, blueberry, roses, forsythis, hibiscus, hydrangea, rudbeckia, hollies, weigela and many other ornamentals.

What you and your customers need to know:
● Customers should plant their newly purchased plant in the proper place in the landscape and help the plant establish. The insect tends to cause problems in the nursery/greenhouse environment but little in landscapes.
● The insect targets new growth as leaves are expanding, and feeds on older leaves. Larvae may be in pots feeding on roots, but cause no visible signs of damage to the plant. Feeding damage causes very little damage to the overall health of the plant.
● They have multiple generations in a year and are difficult to control with insecticides, although work is ongoing.

Information courtesy of Brian Kunkel, University of Delaware

Bagrada Bug

4. Bagrada Bug Poses Threat To Southwest Veggies

Garden center retailers are expected to be knowledgeable not just about the plants they are selling, but how to keep them healthy. This means getting familiar with pests that may threaten the health of these plants. Here’s a look at the bagrada bug, which is becoming a major concern in the Southwest.

Where it’s found: California and Arizona

Why it’s a problem: The population of the bagrada bug has greatly increased in California. Dara says it is mainly a problem in the spring and again in the fall, but it depends on climatic conditions.

Weather may be contributing to the pest’s proliferation. When warmer temperatures prevail, so do the bugs. “Dryer and warmer winter and spring conditions than previous years might have contributed to wider distribution of the pest this year,” Dara says.

Pest facts:

● The bagrada bug targets mainly veggies, including tomatoes and brassica/leafy greens, as well as sunflowers. It causes damage by feeding on newly emerged seedlings.
● Adults are typically most active from mid-morning to late afternoon, when temperatures climb above 90°F.
● When sampling for feeding damage, look for fresh feeding signs on young leaves.

What you and your customers need to know:

● Several weeds may host bagrada bug, so it’s important to keep gardens free of weeds.
● If you can plant sweet alyssum in the area, do so. Sweet alyssum is a beneficial habitat, and the bagrada bug is drawn to it.
● Aside from conventional pest control materials, there aren’t many proven options for managing bagrada bug. Microbials or insecticidal soaps may be an option.
● To find out more on how to manage bagrada bug, check out the Bagrada Bug Management Tips from the University of Arizona.

Information courtesy of Surendra Dara, University of California, and John Palumbo, University of Arizona

Crape Myrtle Bark Scale Sooty Mold

5. Watch For Crape Myrtle Bark Scale In The Southern U.S.

Suppliers of crape myrtle should be aware of a relatively new insect pest that was first found in Texas about 10 years ago and since has spread across much of the Southeast at an alarming rate. Crape myrtle bark scale (CMBS) was first identified in a north Dallas suburb in 2004. By October 2013, it had made its way to the metropolitan Memphis area, and earlier this year sightings were confirmed in Little Rock, Ark.

“Heightened concern about this new pest is based on the speed at which it is spreading and the common use of crape myrtles in landscapes across a large part of the U.S.” says Jim Robbins, a professor and Extension horticulture specialist in ornamentals at the University of Arkansas.

How To Recognize The Pest

Since CMBS is the first and only known bark scale to occur on crape myrtles, it should be easy to identity.

Adult females appear as white or gray felt-like encrustations on small twigs to large trunks, often appearing near pruning wounds or in branch crotches on older wood. On the most current flush of growth and under heavy infestation, distribution may be more uniform. Up close, CMBS is white to gray in color. Careful examination may reveal dozens of pink eggs or crawlers under some of the larger white scale covers.

The most obvious red flag, says Robbins, will likely be black sooty mold, which appears on the bark.
As female nymphs mature, they secrete a white thread that becomes felted or matted into a thick, whitish to grayish scale covering the entire body. Adult females under this covering are wingless and incapable of moving. It is thought that for this species of scale, eggs are laid under the covering (probably late April to mid-May in Arkansas) and the female then dies. When the eggs hatch into first instar nymphs, these nymphs have legs and antenna and are mobile, dispersing over a short period (about one to two days).

It is thought that this emergence occurs beginning mid-May to early June in Arkansas, according to Robbins; however, crawlers were observed on a warm day in January 2014.

At present in the Southern U.S., the number of generations completed in a year for this species is unknown, but it is suspected that CMBS may complete at least two generations in Arkansas. It is possible that adult females and eggs overwinter, but crawlers and later stage nymphs have been observed overwintering in Arkansas under loose bark and in cracks and crevices.

So far, there has been no research to evaluate whether there is a range in susceptibility to CMBS across the hundreds of crape myrtle cultivars.

Which Methods Control CMBS

Dr. Mike Merchant, an entomologist with Texas A&M University AgriLife Extension, notes that while CMBS will likely not kill healthy crape myrtles, it can overstress the tree. Perhaps more problematic, the intense black sooty mold might be a big turn-off for consumers. “In some years, and in certain locations, the scale can detract significantly from the appearance of crape myrtle plantings,” says Merchant.

Current best suggestions for control of CMBS include:
• For heavily infested plants, wash the trunk and reachable limbs with a soft brush and mild solution of dishwashing soap. This will remove many of the female scales and egg masses and make insecticide control more effective. Also, washing will remove much of the black mold that builds up on the bark on infested trees.
• Horticultural oil has not yet been shown to be effective against this insect; however, a winter application of dormant oil to the bark and crotches of the plants where scales shelter may be beneficial. Be sure to use sufficient volume to allow for penetration behind loose bark and into cracks and crevices. Thorough coverage of the tree is especially important when treating with oil.
• Application of systemic insecticides as a drench applied to the root zone has shown the most promise in tests to date. Imidacloprid (Merit or Bayer Advanced Garden Tree and Shrub Insect Control), thiomethoxam (Meridian) and dinotefuran (Greenlight Tree and Shrub Insect Control with Safari) have shown best control when applied between May and July. When drenching the soil with a systemic insecticide, allow several weeks for the product to be distributed throughout the plant.

Crape Myrtle Fact Sheets Available

Additional fact sheets on crape myrtle bark scale, and other crape myrtle pest management tips, are available at the following locations:
• Texas A&M: http://bit.ly/MBlyAJ
• The Crape Myrtle Trails of McKinney (otherwise known as the “crape myrtle city”): http://bit.ly/1bmJW4f
• LSU Ag Center: http://bit.ly/1fAdLtT

boxwood blight free image

6. Quick Facts About Boxwood Blight

Boxwood blight was first discovered in Europe in the mid 1990s and is now widespread there. North America escaped confirmed cases until late October 2011. Since that time, it has been found in most East Coast states, Ohio and Oregon, as well as the Canadian provinces of British Columbia, Ontario and Quebec.

Cause

Boxwood blight is caused by a fungus, Cylindrocladium buxicola. The fungus has also been referred to by two other Latin names, Cylindrocladium pseudonaviculatum or Calonectria pseudonaviculata.

Hosts

Plant species within the genera buxus, pachysandra and sarcococca have been reported as hosts to this fungus. However, there is limited information about the role pachysandra (spurge) and sarcococca (sweetbox) species play as possible vectors for initiating the disease in boxwood. Although the full host-range of this fungus has not been finalized, it is believed that only plants within the family buxaceae can be infected by the pathogen.

Research conducted at North Carolina State University in 2012 indicated a wide range in susceptibility of boxwood cultivars to boxwood blight, however B. sempervirens types were more susceptible in general, with Buxus sempervirens ‘Suffruticosa’ (English boxwood) and Buxus sempervirens ‘American’ (common or American boxwood) especially susceptible..

Symptoms

  • Dark- or light-brown, circular leaf spots, often with darker margins. Leaf spots may grow together to eventually cover the entire leaf.
  • Dark stem cankers or black streaks on stems
  • Straw- to bronze-colored, blighted foliage
  • Leaf drop
  • Less commonly, white fuzzy masses consisting of numerous clumps of spores may be observed on infected stems and leaves with a hand lens under high humidity.

In container boxwood, sometimes only the lower foliage and stems become infected, leaving the tops green and making the plant appear top-heavy. On large field-grown or landscape plants, only one section of the plant closest to the ground on the shaded side will be blighted.

Blighting and defoliation can occur rapidly, with complete leaf loss under warm (64°F to 80°F) and humid conditions. Due to the shady and moist conditions during propagating, young boxwood plants are especially at risk if the pathogen is unintentionally introduced into the growing area.

Even after severe defoliation, root systems of boxwood-blight-infected plants remain healthy and intact, unlike roots infected with Phytophthora. The stems of infected boxwood typically remain green under the outer bark until a secondary invader or opportunistic pathogen attacks this tissue and eventually kills the plant.

How It Spreads

The primary way this disease spread throughout Europe was the movement of infected plants and cuttings. Another significant way this disease spreads locally (nurseries and landscapes) is through contaminated tools and workers as well as by movement of boxwood debris (especially fallen leaves).

What To Do

Identifying measures for preventing and managing boxwood blight in commercial nursery and field settings is a work-in-progress; researchers are in the process of evaluating fungicides and sanitizers, as well as identifying resistant boxwood cultivars. All plants infected with boxwood blight should be destroyed, as the chance of further spreading this fungus is highly probable. Once introduced, limiting movement of this sticky, contagious fungus is very difficult and will only be accomplished by always following good sanitation practices.

Information courtesy of North Carolina State University

rose rosette disease causing phyllody in rose free image

 

7. A Quick Guide To Rose Rosette Disease 

Symptoms. Rose rosette disease manifests itself in different ways, depending on the rose species and cultivar and the severity of the infected plant. Common symptoms include leaf disfiguration and reddening, stunted leaf growth, elongated or thickened stems, excessive thorn production, witches’ broom (multiple stems at the ends of branches) and malformed flowers. Roses with rosette disease may abort blooms and exhibit fewer petals. The petals that do appear are likely to be discolored or have an abnormal shape.

How it spreads. Rose rosette disease is spread via Phyllocoptes fructiphilus, a tiny eriophyid mite. The mite lives between leaf petioles and axillary buds. It is mobile at temperatures above 70°F and inactive at temperatures below 50°F but is not killed in cold weather. These mites can be spread aerially for up to 100 miles, but infestation via this method is a matter of chance. Multiflora rose is the main host of the disease, so limiting the plant will help in reducing the spread of rose rosette.

How to control it. Like downy mildew, there is no cure for rosette disease. Unlike downy mildew, rosette is detrimental to most rose and hybrid rose varieties. The best plan for limiting the disease involves reducing the amount of multiflora rose in the landscape and using chemical controls effective against Phyllocoptes fructiphilus.

When limiting multiflora rose, the best plan of action is to use herbicides and cutback. Pruning can also help in reducing the spread of rosette by removing overwintering mites. Infected plants should be dug up, bagged and discarded or burned immediately. Once infected with rosette, the plants will die.

Miticides that may be effective include Avid, Akari, Judo and horticultural oil. Star Roses and Plants/Conard-Pyle has created the Rose Rosette Disease Guide to educate people on how to limit the disease, which can be a valuable resource when explaining the disease to your customers.

Plant alternatives. Some rose varieties have shown resistance to the disease. One of these cultivars is Rosa bracteata. The plant’s foliage resists the mite and therefore is immune to the disease. Some native rose varieties have also shown resistance, including Rosa arkansana, Rosa blanda, Rosa palustris and Rosa setigera.

What To Tell Your Customers

Because rosette disease always kills the plants it infects, helping homeowners be successful involves educating them on how to stop the disease from claiming plants in their gardens and landscapes.

“I always recommend homeowners destroy symptomatic plants,” says James W. Amrine, Jr, is a professor of entomology at the University of West Virginia, Morgantown. “If the plants are of special value, I recommend they try to find healthy tissue and establish grafts on other roses or develop rooted cuttings in mist beds.”

For some customers, prevention is the key to success.

“If you live in an area with lots of nearby symptomatic multiflora roses, treat with a miticide on a weekly basis from April until late fall, when all growth ceases and leaves fall off,” Amrine says.

Retailers that sell a lot of roses should take a similar approach to those in areas where downy mildew is prevalent. Continue to educate customers using eNewsletters, social media and signage. Staff members should be able to answer questions or direct consumers to the proper sources of information.

Editor’s Note: The information in this article was written with the help of the Create A Plan Of Attack For Rose Rosette Disease webinar sponsored by Star Roses and Plants/Conard-Pyle. See the sidebar for more information.

impatiens downy mildew free image8. What To Tell Customers About Impatiens Downy Mildew

Symptoms. Impatiens exhibiting symptoms of downy mildew may appear different from landscape to landscape depending on how advanced the disease is. Early symptoms include leaves with light-green yellowing or stippling. The leaves may also curl downward, have gray markings on the upper surface or white fungal growth on the undersides.

Advanced symptoms include stunted plant and leaf growth, bare plants as the result of leaf and flower drop and softened, weak stems. Young plants and seedling cotyledons have an increased  likelihood of being infected.

How it spreads. Downy mildew is spread by sporangia, or sac-like structures filled with zoospores on the undersides of infected plant leaves. Because the sporangia easily detach from the plant, they can be spread by wind or water splash. In the landscape, spores can travel hundreds of miles via wind currents, and plants not yet showing symptoms may unintentionally infect those around them in the garden center setting, as well. It spreads most easily in moist conditions.

The problem continues to ravage Impatiens walleriana in the landscape, and gardeners living in states where the disease has been confirmed must be especially careful. In 2011, the disease was found in 13 states, and that number rose to more than 30 states and Washington, D.C. the following year. To see a map of the infected states, go to TodaysGardenCenter.com/March2013.

How to control it. Although there is currently no cure for downy mildew, there are ways to control the disease culturally and chemically. For cultural control, be sure to separate impatiens from different sources. This way, if the impatiens from one grower source includes infected but symptom-less plants, the disease will not spread to the rest of the crop. It is also essential to consistently scout the plants for symptoms and remove any plants or leaves that appear to be infected.

When it comes to chemical protection, a lot of the preventative applications must be completed at the grower level. Be sure to check with your plant suppliers to ensure the crops are being sprayed one week prior to shipping. When working with landscapers, additional precautions must be taken. For more information on how to work with your landscapers on limiting the spread of downy mildew, visit BallLandscape.com.

Plant alternatives. While Impatiens walleriana and its hybrid varieties are at risk, New Guinea impatiens (Impatiens hawkeri) have remained immune. Even at a higher pricepoint, however, many customers are willing to pay more to maintain a colorful landscape. Jim Dezell, owner of Flamingo Road Nursery in Southern Florida where the disease is especially prevalent, found getting his customers interested in alternatives was relatively easy.

“We converted our customers to New Guinea impatiens — at double the price — by telling them they wouldn’t have to worry about them dying and they last a month longer in the summer heat,” Dezell says.

Other alternatives Dezell promoted were SunPatiens, marigolds, vincas and begonias. Although impatiens sold for $0.99, customers doled out $1.29 for begonias and marigolds and $1.99 for vincas, SunPatiens and New Guinea impatiens.

“Customers would much rather spend money on the plants they are not going to have to spray weekly,” Dezell says.

What To Tell Your Customers

Swaying shoppers in the direction of alternatives is only part of the way retailers need to be proactive in educating their customers. The first step is to raise awareness.

“Most people have caught on to the disease now, but when it first became a problem and we stopped selling impatiens, we sent a statement to our email list,” Dezell says. “It included pretty pictures of SunPatiens and vincas and said, ‘Because of the problem with regular impatiens, we are not carrying them.’ It also informed them that the reason was the plants would not last. It was a policy statement written in a friendly way for our customers’ benefit.”

Ned Wilson, owner of Wilson’s Garden Center in Newark, Ohio, used social media and in-store signage to discuss the downy mildew issue.

“Knowing how much of a problem the disease can be and how fast it spreads, we have decided to forewarn our customers of the potential problem if they rely on impatiens as their source of color in their gardens through prominent signage and social media interactions,” Wilson says.

When raising awareness of the issue, however, it is important to have a clear message that focuses on positives.

“We told our customers, ‘Our goal is to make sure you are a successful gardener.’ When they asked why Home Depot still had them, we said, ‘That’s because they have buyers out of the area and they don’t care like we do,’” Dezell says. “After we explained the situation and how the plants looked like they had been through a freeze last year, more people understood. A lot of customers didn’t realize the disease was downy mildew last year — they thought the plants were wiped out due to a cold spell in September.”

Flamingo Road stopped carrying Impatiens walleriana altogether, but many of the retailer’s plant suppliers have indicated 2015 as the year when impatiens will rebound. In the meantime, some garden centers like Wilson’s simply cut back on the amount of available flats.

“We are still offering the wallerana type impatiens to our customers who want to take the risk, but in good conscience, we want them to know the situation in advance,” Wilson says. “We grew several thousand flats of impatiens last year and are planning about 500 this year. These, of course, will be carefully treated to keep the plants disease free at the greenhouse.”

Editor’s Note: This article was written with the assistance of Ball Horticultural Company’s “Grower Guidelines” on Impatiens Downy Mildew and plant pathologist Dr. Colleen Warfield. For the most recent version of grower and retail guidelines, visit BallSeed.com.

Imported red fire ant free image

9. Imported Red Fire Ants Discovered Outside Current Regions

The discovery of imported red fire ants at a Delaware garden center has led to the state Department of Agriculture (DDA) issuing an alert to local businesses and buyers of tropical nursery stock. The detection of fire ants was found in a shipment of palm trees imported from Florida. The live ants were destroyed, but state agriculture officials are urging Delaware residents to inspect tropical plants carefully before buying them.

A federal quarantine is in place for fire ants in 14 southern states and Puerto Rico, covering more than 367 million acres. Faith Kuehn, DDA’s plant industries administrator, says that nurseries or other vendors should check each shipment received from these states for the proper credentials and inspection certificates.

“We are urging caution on all fronts because of the ability of fire ants to spread quickly and the danger they pose,” Kuehn says. “We have had good luck so far, but that depends on prompt reporting and inspections.”

What To Know About Fire Ants

Imported fire ants pose a hazard to both human and animal health and to agriculture. Young animals and young trees are both susceptible, while nests in fields can interfere with cultivation and harvesting. When their nests are disturbed, they can be very aggressive, crawling up vertical surfaces and biting and stinging in a swarm.

For garden center retailers or consumers who have questions or concerns about imported red fire ants, one great resource to visit is the “Imported Fire Ants” page on Extension.org. Information available on the site includes:
• Regional updates
• Control and management
• Information for Master Gardeners
• Regulatory updates, including quarantines

0