Emerald Ash Borer Update 2012

   photo USDA                                                                     

Recent information has confirmed that Emerald Ash Borer has been found in Northern Dutchess County in South Eastern New York. Though not unexpected, it is a milestone to have confirmed its presence this side of the Hudson River.

Do you have a plan in place to protect your valuable Ash trees? Treating your Ash trees before this bug arrives has proven effective in protecting Ash trees from this deadly pest.

Emerald Ash Borer (Agrilus planipennis) was discovered in the Detroit region in 2002 but was likely established in that area in the mid 1990's. This small brilliantly green insect is from China, where it is a minor forest insect living on weakened Ash trees in its native forests. American Ash trees have no natural resistance and are excellent hosts to this pest. Once infested with this pest Ash trees decline and eventually die in 2 to 3 years. Small or stressed trees may die in one season. One mode of transport this beetle shares with other destructive pests is its ability to spread by hitchhiking on firewood.  Quarantines prohibiting the movement of firewood and raw wood products are in place or will be in place in many areas by years end. Efforts to eradicate the pest have been largely unsuccessful, leading one official to describe it as “cutting a hole in a doughnut". The beetles have often spread beyond the site of initial infestation by the time they are detected and treated.  Efforts are taking place to look for naturally resistant selections of Ash as well as locate natural predators that may reduce Emerald Ash Borer's destructive abilities. What can you as a home owner do to be prepared for this pest? If it has been detected in your area you will need to protect Ash trees you want to preserve.

First you will need to assess if you have Ash trees on your property and what the appropriate action you should take. If you have Ash trees and want to protect them, you should maintain the vigor of those trees with appropriate cultural measures. These may include fertilization, root stimulants and mulching. Once EAB is close to your area, there are proven systemic treatments that can prevent infestation by EAB. Preparation and prevention are your best defenses against Emerald Ash Borer damage. The chart below estimates the risk to your ash trees posed by EAB and can be described as follows:

0-5 miles from a known EAB site-                  Extreme Risk,

5-10 miles from an EAB site                           High Risk,

10 miles and greater from an EAB site            Elevated Risk.

If you are in an area that is at elevated risk you should be developing a plan with the help of your ISA Certified Arborist. Take the time to contact your ISA Certified Arborist today and have your property accessed for the potential impact of Emerald Ash Borer. Panic is pointless, preparation is priceless.

Cedar Apple Rust

                                                                               PHOTO TCC

Cedar-Apple Rust, caused by the fungal disease, Gymnosporangium juniperi-virginianae is another serious and disfiguring disease of ornamental and fruit apples. Rust fungi are evolved complex organisms that require two hosts to complete their life cycle.

The first host of this disease is Eastern red cedar, Juniperus virginiana,where the rust forms ball like structures with fungal telial horns that forcibly eject the spores that spread the disease to apples. Although these bright orange horned goo balls are quite alarming they are usually not noticed on the juniper or mistaken for fruit or cones. Once the spores from the juniper travel to the leaves of apples the real unsightly damage occurs. 

On apples the spores germinate and after a week or two cause orange pustules on the leaves of susceptible apples. Rainy wet weather in the spring is ideal for the germination on junipers and the spread and infection to apples.

Once in the apple leaf, given a short period of wet weather, the leaf lesions form fruiting structures in mid to late summer and re-infect the juniper host where the disease over winters. 

Cultural control, includes removal of junipers in the vicinity of apples as well as planting disease resistant varieties of apples. Avoiding mass plantings of apples and junipers in landscapes reduces the amount of disease inoculum and the potential for severe outbreaks.

There are a number of fungicides that are labeled for control of Cedar-Apple Rust. Typically they require several applications starting at bud break and continuing every two weeks to get suitable control. Fungicides may also be applied to junipers in mid to late summer to reduce the back transmission from the apples to the junipers.

Your I.S.A. Certified Arborist is up to date on the latest research on Cedar Apple Rust and can help preserve your apple trees.

Scabs on Your Apple

                                          photo bwg

Apple scab, caused by the fungal disease, Venturia inaequalis is one of the most serious and disfiguring diseases of ornamental and fruit apples. Although the name implies it is limited to apples, this disease can be found on many members of the rose family. The hosts can include apples, hawthorns, fire thorns, cotoneasters, and pears.

The symptoms of this disease are typically olive brown lesions on the leaves and sometimes on new succulent shoots. The scabs are indistinct at the margins and if the infection is severe they may coalesce into larger patches. The patchy lesions can be found on flowers, fruit, leaves and twigs. The tree responds to this infection by prematurely dropping infected leaves.  Repeated severe infections can cause die back after several years.

The disease overwinters in dropped leaves and affected twigs remaining on the tree. Wet spring conditions spread spores and allow them to germinate on the leaves, initiating new infections. The warmer the temperature, the shorter the amount of time it takes to initiate and infection. The peak period of infection occurs when the trees are starting to flower and continues until full bloom. Secondary infections will occur throughout the spring and summer when conditions are wet for long periods of time.

Some cultural control, including disposal of diseased leaves and twigs away from infected trees as well as the removal of all leaves in the fall will help to reduce the intensity of future infections. Planting disease resistant varieties and avoiding mass plantings also reduce the amount of disease inoculum and the potential for sever outbreaks.

There are a number of broad spectrum fungicides that are labeled for control of apple scab. Typically they require several applications starting at bud break and continuing every two weeks to get suitable control.

Your I.S.A. Certified Arborist is up to date on the latest research and can help preserve your apple trees.

Dutch Elm Disease a 1% Chance

                                         PHOTO BG

May 18, 2012

Every year at this time I bring attention to a tree disease that rewrote the book on urban forestry. Dutch Elm Disease is a fungal disease that, after decimating the elm forests of Europe early in the last century, was discovered in New York in the 1930s and has since crossed the continent. Described as 99% fatal to Ulmus americana, the American elm tree,.

Rapid growth and the ability to survive tough urban conditions are two of the characteristics that made American elms the go to tree for urban settings. Graceful vase like shapes lent themselves well to over street canopies and spectacular alles.

The only major drawback was its inability to survive the introduced fungal pathogen Ophistoma ulmi. This disease combined with the presence of a previously harmless bark beetle, created the perfect conditions for a country wide epidemic.

D.E.D. moved at a rapid pace, its sticky spores clinging to the bodies of both native and introduced elm bark beetles. This combined with people moving beetles and diseased firewood spread D.E.D throughout most of the native range of this stately, street tree

With such a high mortality rate there were many who predicted the eventual extinction of the American elm. However, there was right from the beginning tiny numbers of trees that, in spite of being in the middle of epidemic numbers of dead and dying trees, and plagued by hordes of bark beetles, survived,  continuing to grow and prosper.

There have been a number of programs funded and promoted by governments of Canada and the United States that have brought forward many potentially resistant examples of American elm. Through rigorous testing some are proving to be very resistant to D.E.D.

American efforts have resulted in American elm varieties like “ Princeton”, “Valley Forge” and “ Deleware” all of which have been shown to have some resistance to D.E.D. Canadian efforts to date have resulted in several trees of note, “ Brandon” an American elm and Jacan a Japanese elm pioneered by Dr. Wilbur Ronald formerly from Agriculture Canada’s Morden, Manitoba facility. This later selection is in fact growing in Brandon, Manitoba, on 10^th St. and on Pacific Ave. at 15^th St. Jacan does not have the characteristic vase like shape but has proven to be an excellent tree in other respects.

As we move forward in an age of cloning and micro propagation, efforts in Guelph, Ontario spear headed by Dr. Praveen Saxena, have resulted in the ability to mass produce resistant trees. This greatly increases the efforts to grow and test resistant varieties as well as producing them for introduction. With so many skilled and dedicated people working to find resistant American elms, one can’t help but have hope that from the thin numbers of survivors a new generation of elms will emerge and take their place on our city streets

Your I.S.A. Certified Arborist is up to date on the latest research and can help preserve your elm trees.

The Good Scout

In our previous article we discussed the history of pest management on landscapes and how it has evolved over time into I.P.M. Integrated pest management is the combination of cultural controls, like pruning and fertilization, with tree pest and disease control when necessary. This may sound contradictory but it is not, not all pests are at levels that impact the tree and not all diseases significantly impact the health of the plant or its utility in the landscape. Knowing the level of insect and disease pressure on a plant is complicated but always starts with identification. Both the plant and the problem must be correctly identified before the extent of the problem and the necessity of treatment are determined.

The key to identification is having a good scout, you must walk the property identify the trees and shrubs present and know the likely insects and diseases that may impact the landscape. Knowing each and every plant and disease is not possible as insects, diseases and the palate of plants in the landscape are infinitely variable.  Well, we as tree people and gardeners would like to think so, but sadly the variability is somewhat limited.

The scouted landscape patrol puts a qualified technician on your property armed with the tools of his trade, a keen knowledge of plants and there problems, and a variety of solutions to any issues he may encounter. Once the property has been scouted and the pest and disease problems have been recorded on a form or journal, the specialist goes to work correcting them. This may take the form of a spray or root zone injection or it could be a simple as cutting a nest of ugly caterpillars from your cherry tree and correctly disposing of them. Additional cultural treatments could include the removal of a circled root that threatens to strangle your maple or a suggestion that you relocate a sun loving lilac to a spot that is more open. Given the history of the property, kept in the treatment journal or in a file where the scouting reports are saved, the specialist may perform proactive preventative treatments. This may prevent issues that will occur several seasons in the future. For example, spider mites may be controlled in the spring when their population is low and before they cause premature defoliation of your burning bush in the fall. A simple application of horticultural oil at the right time on the right plant can prevent failures in the landscape in the future. By correctly limiting the amount and timing of applications you limit the number of applications that are necessary to catch up later. Reducing the extent and number of applications in your landscape is not only environmentally sound it’s economically sensible.

 Your I.S.A. Certified Arborist is up to date on the latest research and can plan and execute your scouted plant health care program with modern scientific techniques.

Towards The Good Scout

As long as there have been trees and shrubs there have been insects and diseases that live on and in them that reduce their beauty and utility in our landscapes and gardens.

A former professor and colleague, still very much active in arboriculture, would repeatedly regale us with tales of the good old days when you could just spray everything with lead arsenate and DDT. (He did this with a great deal of humor) This pretty well killed everything and life appeared to be good. However the toxicity, both instantaneous and residual was dramatic, indiscriminate and long lasting. Thankfully we have continued to evolve the process of maintaining our trees and shrubs with less and less toxic treatments while relearning cultural methods that require no chemical inputs. Indiscriminate spraying can result in the destruction of beneficial predatory insects, pollinators leading to resistant super pests that are difficult to control.

The discovery of chemical insect and disease controls was heralded as a dramatic breakthrough in both agriculture and horticulture. And it was, however old, time consuming practices such as breeding plant resistance and using cultural methods to limit the damage of pests were largely abandoned and forgotten when this new wave of chemical methods were embraced. Amazingly this “New Wave Approach “occurred in the 80’s, the 1880’s! It didn’t take long for problems linked to residual toxicity, and residue to spill over markets and dinner tables of the country and the world. In 1891 the New York Board of Health seized shipments of grapes and threw them into the river because they had visible traces of “Bordeaux Mixture “a mixture of copper sulfate and lime. Good for the grape eaters, not so good for the Hudson river. A British Royal Commission recommended safe levels of arsenate in food crops in 1903 after a series of poisonings. The British also threatened a ban on imports of American apples in 1925 due to high levels of lead arsenate. The industry continued to develop and expand the use of chemicals.

The realization that we may be harming ourselves and the environments continued to simmer until April Carson’s landmark book “Silent Spring” was published in 1962. This landmark book leads to the development of the modern environmental movement the initial steps towards finding a safer more environmentally friendly approach were called Integrated Pest Management.

Integrated Pest Management seeks to combine cultural, physical, beneficial, and chemical controls into an integrated approach to insect and disease control. Moving beyond I.P.M. the scouted Plant Health Care program puts a trained specialist on site to carefully monitor the trees and shrubs in your garden and orchestrate the correct treatment regime when necessary. The goal is always to minimize the application of chemicals, when possible using nontoxic products or cultural methods to limit the impacts of pests to acceptable levels. All treatments are carefully recorded and reported to the property owner as well as kept on file for future reference. I will continue to discuss the details of this topic in my next article. Your I.S.A. Certified Arborist is up to date on the latest research and can plan and execute your scouted plant health care program with modern scientific techniques.

The Flush Cut Question

In the beginning there were flush cuts and wound paint. And the world of arboriculture was perfect. That was until someone came along, Dr. Alex Shigo, and did the research that showed that both of these practices resulted in increased injury and decay in trees. Shigo turned the world of scientific tree care upside down with the concept of “Natural Target Pruning”

The basis of this concept is that trees have evolved a biological mechanism that allows them to deal with the loss of branches while reducing the impact to the remaining tree. Trees have been losing branches for a long time, 250 million years, in the case of conifers. Angiosperms, the flowering plants, a group that contains such notable trees as, oak, elm, and ash is a group that have a fossil record dating back at least 130 million years. And they are highly adapted and extremely successful in dealing with branch loss.

The tissues of trees are at first glance are all wood, however from a seemingly uniform group of tissues specialized structures are present both macroscopically and microscopically. When trees naturally shed a branch they do so at a point called the branch collar. This point can be quite prominent on many trees and is an enlarged ring at the base of a branch. Beyond the branch collar there are only branch tissues as it marks the separation from the trunk tissues. Also at the branch collar are a group of wound wood tissues that, once a branch has been shed, form a growing callus layer that acts to cover or grow over the wound left by the shed branch. These tissues seal over the broken branch tissue and prevent the further entry of decay organisms into the trunk of the tree. Trees seal damaged wood and don’t heal damaged wood. Painting wounds with toxic paints and tars sealed decay IN the tree and prevented the tree from growing over the wound site.

Shigo also developed a model to describe the process whereby the tree prevents decay organisms that have already entered the trunk tissue from spreading. The tree sets up a set of barriers in the area where the now dead branch tissues come in contact with the living trunk tissue. This concept is called, Compartmentalization Of Decay In Trees. The CODIT concept was developed using many years of field autopsies on trees that had had branches removed. Based on patterns of decay and staining, where the tree was able to wall off decay coming from removed branches, Shigo was able to identify 4 distinct decay barriers, preventing decay from moving up, down, in and sideways in living trunk tissue. This research shed a great amount of light on what we have always been observing in trees.

Considering the amount of time we have spent in the presence of trees it is a wonder that we have only in the last century started to scientifically examine our practices in managing our beautiful co-inhabitants. Your I.S.A. Certified Arborist is up to date on the latest research and can plan and execute your next pruning project with modern scientific techniques.