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Green Thoughts

Natural Predators of Insect Pests

Posted by Kent Pierce on Wed, May 30, 2012 @ 11:36 AM

One of the principal reasons we practice integrated pest management when caring for trees and shrubs is to reduce our use of pesticides, thereby conserving natural predators and parasitoids of insect pests, allowing mother-nature to take care of the pest problem.  These predators and parasitoids don’t always solve the problem and sometimes we have to intervene, but they will oft times do a great job of cleaning things up.

 buglarve

The above pictured predator is a larva, or maggot, of a syrphid fly, and it’s feeding on wooly beech aphids found yesterday on a European, or copper, beech in New Canaan, Connecticut.  The adults are known as hover flies or flower flies.  Hover fly adults have no defense against being predated themselves but in the never ending panoply of fascinating insect behavior adults of some species of hover flies change color to ward off predators, and still other species of hover flies mimic insects like honey bees or wasps that do have special defenses against predators.

This link, from my friend and mentor Dr. Michael Raupp at the University of Maryland, has more information and some great video of these prolific predators. 

Tags: insects, New Canaan, Connecticut, european beech, bugs, pests, beech, copper beech

Box Blight: A New Disease of Boxwood

Posted by Kent Pierce on Fri, Mar 02, 2012 @ 01:44 PM

 

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Photo Provided by Conneticut Agricultural Experiment Station

 

In the fall of 2011 a significant new disease of boxwood, Cylindrocladium pseudonaviculatum, was found in Connecticut and New York, as well as Maryland, North Carolina, Oregon, Rhode Island, and Virginia. The common name for this disease is Box Blight.  It was found in the United Kingdom in the 1990s and in New Zealand in 2002, but hasn’t been seen on the North American continent until the last several months.  It’s not known how the disease was introduced to North America.

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Photo Provided by Conneticut Agricultural Experiment Station


This is a serious disease.  It affects all boxwoods tested so far.  It spreads long distances by introduction of infected plants from wholesale nurseries to retail nurseries to individual properties.  Infected boxwoods can be asymptomatic at time of sale. Once an infected plant is introduced into a landscape spores can move to healthy plants in a variety of ways.  The spores are sticky so they can be moved on pruning tools, birds, mammals like deer, clothing, etc..  Microsclerotia form on fallen leaves and infect healthy plants. Spores can be carried by wind or wind-driven rain over short distances.

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Photo Provided by Conneticut Agricultural Experiment Station


Box Blight has a very rapid disease cycle that can be completed in one week.  Infections can spread very quickly under optimal conditions with temperatures ranging from 64-77 degrees F, especially if humidity is high. The full temperature range is 41-86 degrees F so this is a disease that can spread under humid conditions at almost any time of year.

 

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Photos Provided by Conneticut Agricultural Experiment Station


Symptoms include light or dark brown spots on leaves that coalesce, often in a concentric pattern.  After infection leaves drop and bare twigs often show black cankers.  Symptoms can be similar to two other fungal blights of boxwood, Volutella blight and Macrophoma blight.  To be sure which of these is fungi are present it is necessary to submit samples to a plant diagnostic clinic.  Healthy plants can be infected and killed in a matter of days.

 

What to do?  For the moment, don’t introduce or transplant any new boxwoods to your property.  Follow proper sanitation measures by destroying infected plants, cleaning pruning tools, and raking up and destroying any leaves fallen from infected plants.  Infected plant parts should not be composted or allowed to come in contact with any healthy plants.  There are a few chemical fungicides that have proven effective in protecting established plants.  As yet there are no known organic control measures.  

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Photo Provided by Conneticut Agricultural Experiment Station

 

With this new disease boxwoods have moved to the top of our list of plants we recommend people avoid planting.  Japanese Holly, Ilex crenata, has a very similar look and very few insect and disease problems.  It’s a reasonable substitute although is doesn’t have exactly the same character and can’t be pruned in the same way, at least not with the same look.  

 

For specific advice on how to protect your boxwoods in areas we service, please call us.

 

All Photos provided by S.M. Douglas, CAES


Tags: Boxwood blight, Connecticut Agricultural Experiment Station, microsclerotia

Tick Management and Lyme Disease Prevention

Posted by Kent Pierce on Tue, Apr 05, 2011 @ 11:33 AM

It's spring time and the warmer weather is inspiring everyone to get outside.  Unfortunately ticks are also active again.

For anyone not following us on Twitter or Facebook, comprehensive information on tick management and Lyme disease prevention can be found on the Centers for Disease Control website here:

Tick Management and Lyme Disease Prevention

Tags: Lyme Disease Prevention, Ticks

Winterkill or Winter Drying of broadleaf evergreen trees and shrubs.

Posted by Kent Pierce on Sun, Jan 30, 2011 @ 04:10 PM
Each winter broadleaf ornamental trees and shrubs are often damaged by winter weather.  Susceptible trees and shrubs include evergreens like rhododendrons, boxwoods, mountain laurels, hollies, andromeda, leucothoe, cotoneaster, euonymus, inkberries, and evergreen azaleas.  Newly planted evergreens are particularly susceptible. 

A simple dynamic is responsible for this winterkill damage.  Leaves are always transpiring, even in winter, and as they transpire they give off water.  When it's very cold roots lose some, even most, of their ability to absorb water.  The result is leaves end up with a water deficit, and they wilt and turn brown.  Wind exacerbates the problem.

Snow, which we’ve had plenty of this year, offers considerable although inconsistent protection against winterkill.  The snow helps in three ways. 

The ambient temperature of the earth in southern New England and New York is somewhere just above 50 degrees F.  In winters where there is no snow on the ground and air temps are below freezing, the ground freezes and this inhibits water uptake by roots and contributes to water deficits in leaves.  If there is considerable snowfall, like this year, the snow insulates the soil from the cold air and, because of the warmer ambient soil temperatures below, soil around roots will thaw out and more water will be available to tree and shrub roots.  In turn, water deficits in leaves will diminish or cease, and leaves will be more likely to remain lush and green.

Second, if the snow is high enough to enshroud leaves, leaves will be in a high moisture environment as they are surrounded by frozen water, at least some of which is volatilizing and becoming water vapor.  It’s like a little snow cave.  Any mountaineer who has spent a night in a snow cave will tell you they are relatively warm humid places.

The last way snow helps leaves is by protecting leaves from wind.  Wind in summer or winter has a tremendous drying effect.  It accelerates transpiration and dessication.  When snow melts after a very snowy winter like the one we’re having, it’s common to see a demarcation line in the spring right where the snowline was on a rhododendron, holly or other broadleaf evergreen.   Below the snow line, where leaves were protected from drying winter winds, leaves will be green and lustrous.  Above the snow line, where the leaves were still exposed to drying winter winds, leaves will be wilted and brown.

As great as snow is for trees and shrubs in, it isn’t reliable protection against winterkill. It doesn’t get high enough to protect the upper parts of many susceptible broadleaf evergreens, and in many years it just doesn’t snow much.  A worst-case scenario for winterkill is to have a very cold windy winter with little or no snow.

As Mother Nature is unpredictable, it’s wise to take steps each year before the onset of winter.  There are two things that can be done to protect evergreen trees and shrubs in anticipation of damaging drying winter weather. 

Trees and shrubs can be wrapped in burlap.  This is unsightly to many people, and can also be very expensive.  If interested in this means of protection, we can refer you to reliable landscape maintenance contractors who provide this service each year.

 A more cost effective and also nearly invisible alternative is to apply a winter anti-transpirant to broadleaf evergreen trees and shrubs.  These materials slow down transpiration rates thereby greatly reducing water deficits in leaves, winter drying, and winterkill.

For more information on how your trees and shrubs can be protected, and also what can be done to help damaged plants recover from winterkill damage, feel free to contact us and speak with a Green Cross ISA Certified Arborist.

Tags: winter damage, dessication, anti-transpirants, anti-dessicants, winterkill

American and Litttleleaf Boxwood Problems

Posted by Kent Pierce on Tue, Jan 25, 2011 @ 11:10 AM

American boxwood (Buxus sempevirens) and littleleaf boxwood (Buxus microphylla) are very common shrubs in Fairfield County and Westchester County landscapes.  Landscape architects, landscape designers, and homeowners all love them for their rich evergreen color, dense growth habit, and resistance to deer browsing.  Unfortunately these two shrubs also have a number of damaging insect and disease problems.

Boxwood insect problems include boxwood leafminer (Monarthropalpusi flavus), boxwood spider mite (Eurytetranychus buxi), and boxwood psyllid (Cacopsylla busi). The most common and most damaging of these three insect problems is boxwood leafminer whose symptoms include lumpy (especially on the bottom) and yellowed leaves.  Boxwood mite symptoms include leaves that slowly turn grayish yellow as tiny leaf puncture wounds from these very small insects become more numerous and coalesce.  Boxwood psyllid symptoms are cupped leaves.  This leaf cupping actually shields the insect as it feeds on leaves. Boxwood leafminer and boxwood mite can cause significant damage but are easy to control, even organically.  Boxwood psyllid is more difficult to control but doesn’t do any appreciable damage.

Boxwood diseases are much more difficult to identify and control.  Most boxwood diseases are fungal pathogens, generally referred to by their scientific names: Volutella, Paecilomyces, Macrophoma, Phytophthera, and Thielaviopsis.   These fungal diseases can have very similar symptoms including discoloration of leaves, wilting, dieback, and general decline.  Symptomatic boxwoods often have more than one fungal pathogen.  Positive diagnosis of these diseases is only possible with laboratory analysis.  There are no effective organic or chemical control options for these diseases so management efforts are focused on prevention and sanitation. 

Prevention takes two forms: planting disease free specimens, and maintaining proper cultural practices.  Planting disease free plants is critically important.  When new boxwoods are purchased, roots and soil from root balls should be tested before new boxwoods are transplanted into the landscape.  This is especially important to prevent the introduction of Thielaviopsis as well as plant parasitic nematodes into your landscape.  These two problems typically come from wholesale nurseries and once they are established in your landscape cannot be controlled or eliminated.  Of recent boxwoods we have tested, roughly 25% had Thielaviopsis or parasitic nematodes, or both.  Infested plants should be returned to the nursery where they were purchased.

Another means of preventing fungal disease problems in the landscape is to maintain good cultural practices.  Boxwoods thrive in well drained soils.  Often soils in suburban landscapes are compacted and don’t drain well.  Additionally irrigation systems are often overused.  This combination of compacted soils and over irrigation leads to water logged soils.  Water logged soils are the perfect environment for Phytophthera and Thielaviopsis.  Loosening soil and ensuring adequate drainage at time of planting, and proper irrigation including monitoring of soil moisture levels are critical to maintaining boxwood health.

Additional causes of disease in common and littleleaf boxwoods are several species of plant parasitic nematodes.  Nematodes are non-segmented microscopic worms.  There are thousands of species world-wide which fill many ecological niches.  The few species that attack boxwoods can be very damaging and virtually impossible to control.  Symptoms can be very similar to symptoms of the above fungal pathogens.  Positive identification of parasitic nematodes requires the expertise of a nematologist.  The only management option available to control parasitic nematodes is soil sterilization, which is not practical in suburban landscapes.  These must be control by sterilization at wholesale boxwood growing facilities.  All boxwoods purchased for landscape installation should be tested to be sure you are not introducing infested and disease boxwoods into your landscape.

Green Cross ISA Certified Arborists can assist you with identification and management of all of these boxwood problems.

Tags: diseases, insects, boxwood

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