Expected benefit of treating crape myrtles for new scale

Two ‘Natchez’ crape myrtles demonstrate the potential impact of bark scale on the size and number of blooms in early summer. The tree on the left was treated seven weeks earlier with the insecticide dinotefuran, the one on the right was left untreated. Note the smaller blooms and mold-covered bark on the untreated tree. Click on the image for a closer view. Photo by Jim Robbins, U of Arkansas.

Earlier this year I posted some information about a new scale pest that is attacking crape myrtle trees in Texas and other parts of the south. It is called the crape myrtle bark scale, Eriococcus lagerstroemiae, and its range continues to expand. This year the scale has jumped from north Texas to College Station and, more recently, Sugarland in the Houston area.

We do not see this scale killing crape myrtle; but like many sap-feeding scale insects, these little scales can stress and reduce the appearance of the trees. They also produce large amounts of sticky "honeydew" that can coat the leaves and anything under the tree (including freshly washed cars). Thanks to Drs. John Hopkins and Jim Robbins of the University of Arkansas Cooperative Extension Service, we can now show you what we believe is likely to be another impact of these scales on trees--namely, smaller flower clusters and reduced blooming.

The above picture was taken of two trees at a church in Little Rock, Arkansas.  The tree on the left was treated with Zylam^® Systemic Insecticide on the 28th of  May, and the one on the right was left untreated.  Zylam^® (active ingredient dinotefuran) was applied as a drench in 5 gallons of water between the trunk and a circle three feet away from the trunk.  The picture was taken seven weeks after the treatment was made. Note that this picture is not the same as a scientific trial, which would involve more trees to ensure that the differences seen here were not accidental.  Nevertheless, according to Dr. Hopkins, scale numbers and honeydew were noticeably less on the treated tree.  And there was a difference in the average bloom size between the treated and untreated tree, with blooms being noticeably larger on the treated tree.

John estimated that the cost to treat the tree on the left with Zylam would be approximately $39--not cheap, especially with multiple trees to treat.  But at least you, and your customer, can see what the expected benefit from a tree treatment might look like.  For a consumer-oriented discussion of the scale, clip and use this link: http://citybugs.tamu.edu/2014/08/14/crape-myrtle-bark-scale-reduces-bloom/

What about the bees?
To date the most promising treatments for crape myrtle bark scale have been the neonicotinoid insecticides,  Readers of this blog should know about the growing concern about the impact of soil-applied neonicotinoid insecticides on honey bee and pollinator health.  So should we be using these products on a flowering tree like crape myrtle? Although date on pollination rates on crape myrtle seem to be lacking, these trees do not appear to be highly attractive to bees (entomophilic). Currently I don't believe that a properly applied soil insecticide (following label directions) will have any significant impact on foraging bees.  But if anything changes in that formula, I'll be sure to let you know. And be sure to read the labels on these neonicotinoid products carefully.  New, pollinator-friendly labels are coming to the market this year.  In the meantime, Extension will continue to look for less susceptible varieties of crape myrtle and possibly safer, less costly treatments for this scale.

Bee protests are cute, but...

A recent protest by organic activists outside a Chicago Home Depot highlighted something of the current debate over pesticides and bees.  It also reminded me that no one wants to go on record as being "against the bees".  Check out the video above.

The folks in the bee costumes in the above video are protesting the retail sale of "bee-killing" insecticides called neonicotinoids. They represent groups demanding that these insecticides not be sold, and that stores begin selling only nursery plants that have not been treated with these insecticides. I've blogged about this issue in the past, and reported on some recent urban incidents that could affect the pest control industry.

Over the past few days there has been some interesting discussion on this subject in a chat group that I belong to. I thought I would share some of the more interesting comments and new studies on the subject.

• Bee experts are mostly in agreement that Colony Collapse Disorder (CCD) in honey bees is not as simple as "bad" pesticides. In fact pesticides may have little to do with bee declines in some areas.  Australia may be instructive in this regard. Australia uses neonicotinoid insecticides like the rest of the world, but Australian honey bees are not in decline. A new Australian government report out this month confirms as much, and concludes that take as a whole, neonicotinoid use has led to an "overall reduction in the risks to the agricultural environment from the application of insecticides." 
• A recent collaborative paper in the journal mBio, by Chinese and U.S. scientists, found a virus that has been known for many years, tobacco ringspot virus (TRSV), that is infecting honey bees.  This virus is the first known plant virus that has mutated and adapted into an animal-infesting virus.  It appears to be transmitted to bees via pollen, and also by varroa mite. And its presence in bee colonies appears to be associated with gradual declines in bee colony vitality.
• In fact, varroa mites in combination with viruses are currently under close scrutiny as a major explanation for CCD.  According to Dr. Richard Cowles, with the Connecticut Agricultural Experiment Station, "When combined with work on Israeli Acute Paralysis Virus and a demonstration that irradiation of hive equipment from CCD could prevent nukes from succumbing to CCD, the strongest evidence for the cause of CCD is the varroa/viral combination."  An interesting side observation is that Australia does not yet have varroa mite, which lends strength to the argument for a mite-vectored virus explanation for the disease.
• Most studies that have found neonicotinoids in pollen have been on herbaceous plants. In one study on red maple trees, a dissertation by Dr. Josephine Johnson at the University of Maryland, no imidacloprid was found in tree nectar and only extremely low levels in pollen (bees feeding on these trees had no evidence of insecticides, nor in hive collected nectar).  So if you do neonicotinoid root applications on trees per label instructions, there is no evidence right now that such applications pose any risk to pollinators.
• Two new Washington State University Extension publications are now available on CCD and neonicotinoids.  The first publication by Lawrence and Sheppard, provides an overview of the problem with an explanation of the various factors thought to contribute to CCD.  How to Reduce Bee Poisoning from Pesticides is a thorough overview of practical ways to reduce the risk of bee poisoning due to pesticides, and includes a table of most commonly used pesticides with their potential risks to bees. 

None of this is to say that there are no legitimate concerns about the toxicity of neonicotinoids to pollinators. These products are certainly toxic to bees, and at levels lower than previously recognized. But research in this area is ongoing, and our understanding of the possible factors that might be hurting bee populations is much better than it was a few years ago. Despite what you might hear, both EPA and the pesticide industry is taking pollinator concerns seriously and is acting to make sure that you have safe tools to control pests effectively. After all, who wants to be "against the bees"?

Honey bees at center of controversy

Neonicotinoids are toxic to bees and other
pollinators, especially when sprayed directly.
Applications of neonicotinoids directly to
flowering plants during daylight hours should
be avoided, per label directions.

What could present a more peaceful, bucolic image than the scene of beekeepers tending their bee hives? Beekeepers are traditionally seen as the gentlest of agriculturalists, not killing anything for food but merely reaping the labor of an industrious insect in exchange for nurture and protection.  Yet there is little peaceful about the verbal and political battle swirling about beekeepers and honey bees at the moment.

In case you haven't heard, the domestic bee industry in the U.S. and in other countries around the world was hit hard in 2006 with puzzling bee and colony losses, since referred to as Colony Collapse Disorder (CCD).  In a typical year beekeepers expect to lose 10-15% of their colonies to disease and various stresses.  Since CCD arrived, colony losses have averaged 30% each winter, a significant increase.  Despite dire headlines warning of the doom of agriculture, according to one 2012 report, the costs of CCD to consumers so far seem to be minimal and honey bee colony losses have been compensated for effectively by beekeepers themselves.

Nevertheless, something seems wrong with the world if bees are dying. And when a possible cause of bee declines is a pesticide, the debate is sure to get lively.

The USDA, university researchers and EPA have been mostly united for several years in the position that CCD is the result of multiple causes including parasites, lack of nectar source diversity, diseases, and overworked bees.  However some recent research on neonicotinoid insecticides has raised alarm bells for critics, and has even led to a temporary ban on this group of insecticides in Europe. The research in question includes laboratory studies with bees and field studies with bumblebees, thought to be more sensitive to insecticides than honey bees because of their smaller colony size.

The smoking gun for environmentalists opposed to neonicotinoids came in the form of studies reported last year that show that one of the sub-lethal effects of low exposure neonicotinoids include loss of the bees' sophisticated ability to find their way back home. This loss of homing ability would account for one of the more distinctive symptoms of CCD, namely colonies that slowly decline with no signs of dead bees around the hive. Other forms of colony decline typically include dead bees around the colony entrance.

While there is no doubt that neonicotinoids are toxic to bees at high enough doses, scientists are still divided on the question of whether bees that forage on neonicotinoid-treated crops are exposed to high enough levels of toxicant to suffer from flight disorientation, and whether there is even a correlation between CCD and neonicotinoid use. Indeed, in some parts of the world where neonicotinoids are extensively used, such as Australia, CCD is not reported to be a problem.

If you work in the pest control industry, by now you should be asking yourself the question, "If my company uses neonicotinoids on a customer's property, are we harming our community's bee populations?"  No one wants to be a bee killer.

If scientists who study bees are divided on the cause of bee risks from pesticides, it's likely that the answer to this question will be complex. But here are some points that might be useful as you consider how to handle this issue within your own company, and in discussing these insecticides with your customers.

• Both the USDA and EPA recently issued a report summarizing positions that CCD is a result of multiple factors, not just pesticides. 
• All labels are approved on the basis that when used according to label directions the pesticide must  not pose unreasonable adverse to humans or the environment, including honey bees.  The EPA has recently reviewed registrations for some of these insecticides and stands by its risk/benefit assessment that these products can be used safely if the label is followed.
• While research is suggestive of a potential risk to bees from agricultural uses of neonicotinoids, the case is far from proven. And so far, to my knowledge, no credible sources have suggested that urban residential uses of neonicotinoids pose any unusual risk to bee colonies in urban areas. 
• The greatest potential risk to bees from neonicotinoids appears to be in agricultural settings, where bee colonies are exposed to large acreages of treated plants.  The diversity of plants and the relatively low use of pesticides in urban settings argues for lower potential risks in residential and commercial landscapes.
• Although neonicotinoids, like most nervous system toxins, are relatively toxic to birds, there is no pattern of bird deaths associated with appropriate use of neonicotinoids, as claimed by some.
• Neonicotinoid insecticides are moderately low in toxicity to people and mammals due to some unique nerve junction differences between us and insects. Just because an insecticide is toxic to bees doesn't mean that it has broad ecological toxicity. 
• Use of neonicotinoid sprays should be avoided on flowering plants during daylight hours.  Bees are at high risk when sprayed directly, or if they contact wet spray deposits.  In residential and commercial landscapes, neonicotinoids can often be applied effectively through root injection, greatly minimizing risks to pollinators like bees.

If your company includes neonicotinoids in its IPM toolbox, take a look at how you are using these products. If you are using products like Premise®, Merit® or Optigard® outdoors, are you restricting sprays to non-plant surfaces, plant root zones and soil?  Are your technicians aware of the risks and possible negative public perceptions of neonicotinoids, and are they well-informed enough to communicate how your company minimizes environmental risks when they are used?

Neonicotinoids are effective and valuable insecticides for a variety of structural and landscape pests. For some landscape pests there are no highly effective alternatives. It's up to all of us to ensure that these products are used safely and in accordance with label instructions. Good product stewardship is essential if we want to keep the use of neonicotinoids and maintain a "green" reputation in our communities.

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NOTE: Neonicotinoid insecticides are a relatively new class of systemic insecticides that make up approximately 20% of the global pesticide market. The first neonicotinoid to be introduced to the pest control market in the U.S. was Premise®, the first non-repellent termiticide.  The active ingredient in Premise®, imidacloprid, remains at the center of the CCD controversy because of its widespread use in agriculture and in the ornamental landscape market.  Other common neonicotinoids mentioned in the bee controversies include chlothianidin (Arena®), thiamethoxam (Optigard®), and to a lesser extent, acetamiprid (Transport®).  Neonicotinoids are important insecticides for the control of termites, fleas, and bed bugs, and outdoors against sap-feeding insects such as scales, aphids and whiteflies.