Water Molds Impacting Trees, Shrubs & Lawns

We've already mentioned in a previous post that this year has been particularly rainy (twice as wet as last year, in fact). In addition to producing a spike in insect activity, the weather has also been ideal for a set of diseases known as water molds (a type of fungi) that impact both woody plants and grasses.

Water molds spread via "swimming" spores that move easily through water. That means frequent rain and the resulting saturated soils both improve conditions for the pathogens. The movement of water above ground helps to spread the molds to new plants, and perpetually wet or damp soils allow them to thrive.

Phytopthora

Phytopthora spp. is a set of water molds responsible for several very serious tree diseases, including Sudden Oak Death and Beech Bleeding Canker. It also affects Maples and other hardwood trees and shrubs, primarily in their root systems. Due to the especially wet weather this year, we've seen a lot of Phytopthora root rot in the landscape. In most cases, symptoms of decline above ground (small leaves, stunted growth, dead twigs) are traced back to the root system (where there is often discoloration, noticeable rotting, and sometimes lesions on thicker roots and even at the base of the stem). 

To preserve an infected plant, treatment for Phytopthora is critical. In addition to applying controls for the disease, making environmental changes that improve drainage and keep the root system of a plant from being saturated with water is incredibly important. (In fact, sprinkler systems can be just as damaging as heavy rains in this respect -- just one example of why it's important to take all of the factors in a plant's environment into consideration.)

Pythium

Another water mold, Pythium spp. causes a number of diseases in turf-grass, including Pythium blight and Pythium root rot. Both of these diseases spread quickly and create irregular patches of brown grass on a lawn. With the blight, grass will often be wet or greasy first, turning later to a more dried out brown. You may also see fungal threads growing above ground on turn infected with Pythium blight. The root rot, on the other hand, is less obvious above ground, presenting as dead brown patches. The roots, however, are obviously rotten and discolored.

Ryegrass is especially prone to Pythium problems, as are bluegrasses and fescues. As with the Phytopthora, controls are available, but fixing drainage and irrigation problems is just as, if not more, important. Certain practices, like refraining from mowing grass when it's wet, will also help prevent the spread of these diseases.

- Ken Almstead, Arborist in Riverdale & Lower Westchester NY

Rainy Weather Means More Insects

Scale insect infestation
on a Maple

Have you been caught in a downpour or two this year? It might not surprise you to hear that we've had twice as much rain this growing season than we did in 2010. Here's a snippet from Cornell Cooperative Extension's July 2011 Newsletter for Professional Horticulturalists in the Hudson Valley:

According to the NOAA, March – May was the wettest 3 month period on record for New York State since weather recording commenced, 117 years ago! Here in Westchester County, we officially started taking 2011 seasonal records on March 15, and since that time, we have accumulated 20.90” of precipitation - with 5.95” of this precipitation having fallen in the month of June alone. When we compare these numbers with 2010, we note that we have accumulated over 2x the amount of precipitation (both for the month of June and the season) than we had received this time last year.

So, what does that mean for conditions in the landscape? A number of things, but let's stick with a major one for the purposes of this post.

More Insects

Lace Bug damage
to Azalea leaves

Mosquitoes may come to your mind first, but the wet, warm weather has also been ideal for a range of insects that impact all sorts of plants, including trees and shrubs. Scale insects have been especially prevelant this year, with heavy infestations showing up on Maples, Dogwoods, Rhododendrons, Azaleas, Taxus (Yews), Cherries and Plums. Another prevalent pest this year is the Lace Bug, which gnaws on the leaves of both Azaleas and Andromedas. The Hemlock Wooly Adelgid has been especially active this year as well.

Untreated Hemlock Wooly
Adelgid infestations can be
fatal to trees in just a few years

Fortunately, while some are quite serious, all of the insect populations mentioned here can be managed with proper programs. However, it is definitely important to take action, and the sooner the problem is dealt with, the better. Why? The smaller the population, the easier the problem is to control. Plus, prolonged exposure to insect damage tends to negatively impact the strength of a plant in future growing seasons even if the problem has been corrected.



- Jeff Delaune, Almstead Arborist in Larchmont, Mamaroneck & Rye

Image Credits: Lace Bug by Whitney Cranshaw, Colorado State University, Bugwood.org; Hemlock Wooly Adelgid by Robert L. Anderson, USDA Forest Service, Bugwood.org; Scale by Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Bugwood.org

Pruning the Cherry Trees at Men in Black Headquarters

A thank you from the Men in Black
Set Department

Here's something a little out of the ordinary for us in the tree business...

The Set Decorators for the upcoming movie Men in Black 3 enlisted Almstead to prune three Cherry trees framing the entrance to the Triborough Bridge and Tunnel Authority in Battery Park (better know to fans as Men in Black Headquarters).

The request was for us to prune the trees back significantly to gain more visibility of the building while still maintaining a natural shape and not making fresh cuts large enough that they would be obvious on screen. While this job required a bit more meticulousness than usual, it's not unfamiliar territory for us. We call this type of work a "natural crown reduction" in arboriculture. In this case, the crew did a great job of removing about 25% of each tree's canopy while still maintaining their natural growth habits and avoiding that "just pruned" look.

Almstead crew pruning Cherries at the Triborough

Bridge and Tunnel Authority in Battery Park

In addition to the aesthetic benefits, natural crown reduction is also much better for trees in the long run compared to less subtle methods like topping (simply cutting back the edges of the crown to where you want them the same way you might shear a hedge). Making cuts at natural junctures in the tree and thinking about which branches are most important to its underlying structure keep future growth headed in the right direction, prevent stress reactions like water-sprouting, and minimize the chances of decay as a result of the pruning wounds. It's definitely the best way to reduce the size of a tree, even if your landscape isn't about to be Hollywood's next big star.

-- Chris Busak, Arborist in NYC & Lower Westchester