Fire Blight is No Delight

As an arborist, I can spot spring coming in February when a faint reddish tinge starts to color the woods.  This tells me trees are starting to stir, and warmth will soon be on its way.  Despite the early clues that I am looking for, I am always amazed by the vibrancy of life once trees have fully emerged.  Yes, I love the stage when trees are flowering, but somehow once trees are fully leafed out they look so alive, so perfect, so unblemished.  No bugs, no drought stress, no fungal diseases – just full, green leaves.

And then… pests and pathogens let us know that they have been waiting for spring as well.  What can we say?  Life the way we know it is varied and expressed by many different forms, each trying to survive in its own way.

This year has been a particularly bad one for fire blight on Pear and Apple trees.  Fire blight is a bacterial disease that affects plants in the Rosaceae family, causing a characteristic blackened wilting of leaves and twigs. This family of plants is also popular for its landscape value, both for flowers and fruit production. Pear, Cherry, Rose, Apple, Serviceberry, Cotoneaster, Hawthorn are just a few trees and shrubs that are very familiar to us. Have you noticed a profusion of dead, blackened leaves in your neighborhood? In your trees?

There are ways to stave off the progression of the disease, even now. Ideally, the trees would be treated earlier in the season for better control, but a combination of steps are recommended for trees that are highly susceptible to the disease. Treatment steps vary depending on how affected your tree is.

Thanks for being our client, and for loving your trees! I’ll see you out there.

Your friendly neighborhood arborist,

José Fernández
ISA BCMA® OH-5129B

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3 Tips to Check for Fire Blight

1. Check if your tree's leaves are browning only at the tips of the limbs

2. Check if limbs have the "Shepherd's Crook" (FYI - The Shepherd's Crooks doesn't always occur in trees infected with fire blight but it an obvious sign of the Fire Blight inspection.)

3. If you suspect your tree has fire blight, please click here or call 614-895-7000 and we'll send a Certified Arborist to review the tree and give you a quote to treat the issue

Watch out Crabapples! Apple Scab is a Major Threat!

Plant diseases love Spring! As temperatures warm and tender new growth emerges, conditions are ideal for pathogens to settle in and take up residence in our favorite trees. It is now when many plants are susceptible and treatable for diseases, such as Dothistroma needle cast of Austrian Pine, Rhizosphaera needle cast of Blue Spruce, rust diseases on hawthorn and pear, and for the purpose of this article: the aesthetically devastating apple scab on flowering crabapple.

What is apple scab and what does it do?

• Apple scab is caused by the pathogen Venturia inaequalis.  It is a common disease targeting the rose family of plants which includes crabapple, apple, pear, hawthorn, mountain ash, cotoneaster and pyracantha.
   

• Apple scab produces lesions on leaves, flowers, fruit and on young succulent shoots.  When infected areas are numerous, leaves can become curled and distorted and severe infections can lead to complete defoliation of trees and shrubs.
   

• Several years of early leaf loss generally results in poor growth, reduced bloom and increased susceptibility to winter injury and insect predation.

How does the disease work?

• Apple scab overwinters in fallen diseased leaves and in the soil.  Disease development is favored by wet weather and cool temperatures that generally occur in central Ohio in the Spring and early Summer.  Fungal spores are moved from the ground and carried to trees by raindrop splash and wind where they make their way to leaves, flowers, and fruit.  
   

• During wet periods, newly emerging crabapple leaves are extremely susceptible to infection.  The longer the leaves remain wet, the more significant the infection can be. 10 - 20 days after initial infection, new spores are released which infect new leaves.  Repeated infections can continue through the summer until environmental conditions become too hot and dry for the pathogen.

What can be done to protect my crabapples?

• For most cultivated varieties of crabapple, fungicides must be applied preventatively to successfully manage apple scab.  Fungicide sprays should begin when the first green leaf tips are emerging with additional sprays being applied in roughly 2-week intervals.  The number of fungicide applications needed can vary with weather conditions but generally, we recommend 3 separate applications.
   

• Other cultural practices that can increase the effectiveness of fungicide applications when managing apple scab are:

1. Raking up and destroying fallen leaves to reduce locations where the apple scab pathogen can overwinter

2. Space crabapple trees generously to increase air circulation around trees

3. Prune out crossing limbs, vigorous upright sprouts and suckers to increase airflow and sunlight penetration into the canopy (this can help foliage dry faster after rain or dew)

4. Avoid overhead irrigation, if plants need water, apply water directly to the root zone.

Additionally, much breeding and selection work has been performed to introduce scab resistant crabapples into the landscape.   A short list of some of the most resistant cultivars includes:

• Coralburst

• Donald Wyman

• Prairiefire

• Purple Prince

• Red Jewel

• Royal Raindrops

• Sugar Tyme

Other common fungal diseases of plants that can be managed through the use of our fungicides include:  Oak Wilt, Dutch Elm Disease, Powdery Mildew, Anthracnose and Verticillium wilt. 

Neonicotinoid Use in Ornamental Landscape and Effects on Honeybees

Neonicotinoids are chemical products that are effective in systemic control of insect pests in plants.  Systemic application of insecticide has multiple advantages over other methods, such as topical applications.  When applied systemically, neonicotinoids are absorbed by the plant, and persist for a longer period of time, so that insect pests subsequently feeding on plant parts ingest the chemical and die. 

Because of this mode of action, there has been concern about neonicotinoids persisting long enough to be found in plant products such as nectar or pollen, where they could be ingested by foraging bees.

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I have been following this topic for several years, collecting various articles that have been trickling in.  As licensed commercial applicators, we are trained that “the label is the law”, so pesticide applications to plants are always made according to label instructions.  However, there have been claims made about neonicotinoids causing problems for Honeybee populations.

I have personally attended seminars here in Ohio where scientists leading research on neonicotinoid use for controlling invasive insect pests have stated that despite some claims to the opposite, there have been “no documented studies” proving a relationship between neonicotinoid use and Honeybee decline.  Since then I have read some articles referring to studies that seem to show a correlation, but no conclusive proof.  As an applicator who cares about the welfare of beneficial insects, the lack of conclusive studies is a source of frustration.  In fact, the approach I was leaning toward was “if there is a high level of uncertainty, perhaps it is best to seek alternatives for treatment, or to not treat at all”.  There is a lot to consider when deciding whether or not to treat a plant chemically, but that topic is beyond the scope of this article.

What is the issue with neonicotinoid use and bees?  The reason neonicotinoids are great options for pest control are ease of application, larger windows of application timing, and more targeted applications.  Using topical sprays to control pests requires very specific timing (pest usually needs to be present at the time of spray), and there is a risk that other non-target plants may get sprayed (wind drift).  Also, non-targeted insects present at the time of application can come into contact with the chemical.

A systemic application is much simpler: no spraying may be required (usually applied as liquid drenches into the soil around the root zone of the target plant, or injected directly into the tree), only insects feeding on plant tissue are targeted, and timing is much less critical since the chemical resides within the tree, eventually breaking down so reapplication is necessary for continued control.  And this is the question raised by many concerned people: If the plant tissue has enough chemical to kill insects feeding on the plant, isn’t it possible that the nectar produced by the plant’s flowers will be laced with the chemical as well?  So how does this affect bees?  These are very reasonable questions, and I agree that they merit consideration.

I was intrigued to see Bernadette Mach (Department of Entomology, University of Kentucky) on the speaker schedule at the Ohio Chapter ISA Tree Care Conference in Columbus, Ohio, this year.  Intrigued, because she was speaking on the topic of neonicotinoid levels that persist within a plant after treatment, specifically in nectar.  Her talk was in two parts, both of which applied to our concerns as commercial applicators.  The first half dealt with her studies on which flowering plants were attractive to bees.  The second half was measuring residual levels of systemic chemicals in nectar following application at label rates during different times of the year.  Details of her study informing the second half of her talk can be found online (Uptake and Dissipation of Neonicotinoid Residues in Nectar and Foliage of Systemically Treated Woody Landscape Plants). 

In short, there were several important details that I came away with:

1. Of two chemicals commonly used, one has a lower residual in nectar than the other.
2. The timing of the application matters.  Applications made post-bloom had a low residual in nectar the following year.
3. For some plants, the issue does not matter.  For example, Boxwood, in particular, has caused me difficulty.  Leafminer is a very common insect pest that can destroy Boxwoods, but it can be readily treated with a systemic application.  Last season I began communicating with clients my concern over treating Boxwoods and potential harm to bees.  After communicating with Bernadette specifically on this topic, I feel more comfortable continuing with Boxwood treatments as usual.  The reason is that Boxwoods are not a plant that attracts bees, so there is a greatly reduced risk that they would feed on the nectar.

As a Certified Arborist and licensed commercial applicator making recommendations to clients, I need to consider each plant prior to treatment.  Yes, the client wants to control Magnolia Scale, but should we attempt to do so systemically?  Is this plant attractive to bees?  If so, should we time the application post bloom?  Will this concur with the insect life stage being targeted?  What about other options?  Can we apply a targeted topical spray that will be effective?

In some cases, nothing more will be possible than to explain to the client the implications of treatment.  For example, if the client has a Hawthorn that consistently looks ugly each season when the leaves turn brown and blotchy due to Hawthorn leafminer, I can explain that the best way to control this pest is with a systemic application in the fall (which is essentially pre-bloom) to protect the tree from the pest in spring.  This means that there will be higher levels of neonicotinoid in the nectar the following spring, and since bees are attracted to Hawthorn blooms there is a chance they may be affected by the chemical.  Leafminer in Hawthorn causes damage that is mostly aesthetic.  Once the client considers all this, she may simply choose to leave the tree untreated and deal with some less than perfect leaves. 

Ultimately Certified Arborists that are licensed commercial applicators will be making applications based on label recommendations provided by the specific chemical manufacturer.  However, we need to follow the thought process outlined above to make responsible decisions, understanding that our choice of which chemical to use when to apply it, and how to apply it may have effects that reach further than simply trying to save one plant, or make it look better.

José Fernández
ISA BOARD CERTIFIED MASTER ARBORIST® OH-5129B
ODA COMM. PESTICIDE LIC. #105859 (Categories 2B, 4A, 6A, Core)
TREE RISK ASSESSMENT QUALIFICATION (TRAQ)

Did You Know Construction Can Kill Trees?

We see it all the time: trees surrounding a newly built home dying as a result of soil compaction and mechanical damage from heavy machinery, as well as change in the native grade affecting soil depth and water flow. A tree preservation plan is needed prior to construction which prioritizes your woody landscape as an important part of your construction project. With a Pre-Construction Tree Preservation Consultation from Arbor Answers, our experts will build a custom plan for your construction site to encourage the trees to thrive following the completion of the project. 

Options for the Pre-Construction Tree Preservation Consultation:

• On-site meeting to discuss construction plan and desired trees on the property

• Customized plan to help protect your trees during and after construction

• Installation of temporary fencing to give trees proper perimeters (if needed)

• Installation of temporary root zone protection (if needed)

Contact us before you build to maintain the beautiful wooded landscape you desire!