European Pine Saw Fly

These gregarious larvae will wave in unison as you approach and resume munching on your Mugo pine as soon as you leave. This joint reaction is thought to deter predators from  the feeding colony.

The European Pine Sawfly, Neodiprion sertifer, is the larvae of a non-stinging relative of bees and flies. It is as its name would imply a native of Europe and was accidentally introduced into North America in the late 1920’s.

Young first instar, the larvae as it emerges from the egg, feed on new soft growth on conifers in late April to early May. As they grow they will move to feeding on older last year’s growth. The preferred host plants are two needle pines like, Jack pine, Scots pine, and Japanese two needle pines. They have been known to feed on red pines as well as white pines.  

The larvae feed in large groups of 40 to 200 individuals; this limits the effect of predators as well as creating local areas of intense feeding. This feeding can disfigure and even kill individual branches in specimen trees. Though seldom fatal too host plants repeated infestation can reduce the vigor of healthy trees and leave them susceptible to other diseases and insects.

Once the larvae grow and develop through a series of instars, larval stages, they migrate down the tree to the soil where they spin a cocoon. In the cocoon they transform into wasp like creatures. The adult forms emerge in September and October, quickly mating and laying eggs on the needles for next year’s generation.

The fertilized female lays groups of the small yellow, rice shaped eggs. These are  laid or glued as a sticky elongate coating on needles in the upper branches of the tree. The eggs overwinter, emerging to start the cycle next spring.

Control can be as easy as hand picking needles with eggs off the pines in the fall, or spraying them with a blast of cold water in the spring. Insecticidal soap is effective if applied to the early stages of larvae. Once the larvae are in the final instar, last stage before they descend, they have stopped feeding. This makes control ineffective. Chemical control is available and should be applied according to label direction.

If you have ornamental pines ISA Certified Arborists are industry recognized experts in plant insect control. Contact your I.S.A. Certified Arborist to see if you have this damaging plant pest.

For more information on this subject or any plant health care related questions please feel free to ask Professor Tree at the link in the right margin. 

Spots On Your Apples

 

 

 

 

If you would like to not have spots on your apples and leave the birds and the bees this article may be just what you’re looking for. Apple Maggot, Rhagoletis pommonella, is a small fly that infests a variety of hosts including crab apple, apples, plum, hawthorn, and occasionally apricots. It has a wide range from North Eastern United States through to Southern Manitoba, Canada

The spots on your apples are created when the female of the species punctures the skin of the fruit laying her eggs. The eggs then hatch and burrow though the apples causing the characteristic traces or brown discolored tunnels in the flesh of the fruit. The plant often responds by dropping infected fruit. Once the fruit is dropped the larvae emerge and pupate in the soil under the host tree. Some fruit remains on the host until fall and larvae develop at a slower pace in these fruits. This leads to a long period of emergence for adults in t the following spring.

Adults emerge the following spring just after the apples have finished blooming and continue to emerge for the next two months. The insects are small flies, slightly smaller than a house fly with black bodies and distinctive black bands on their clear wings. They emerge sexually immature and take a week to 10 days to fully develop. While maturing they feed on honeydew secreted by aphids. Once mature they congregate and mate on fruit.

The female lays as many as 300 eggs in her 30 day life span.

Control of this pest is difficult due to the long period of adult emergence. Chemical controls can be effective if applied at the very end of the flowering period and every 10 days thereafter until the adults are no longer emerging. Time applications to begin after flowers start to loose petals and you will have minimal impact on pollinators such as bees. Horticultural oils can reduce the population of aphids and limit food sources for immature adults. Bright red plastic sticky apples and yellow paper sticky traps can be used to scout for the emergence of adults. Culturally, prompt removal of all dropped apples throughout the season helps to break the life cycle. Dropped apples should be disposed of sanitarily off site. Removing alternate hosts in wild adjacent areas will also help to reduce populations. 

If you have questions about apple maggot contact your I.S.A. Certified Arborist to see if you have this damaging plant pest.

I.S.A Certified Arborists are industry recognized experts in plant insect and diseases control.

Frost Cracks and Sun Scald

Winter’s severe cold weather takes its toll on all of us and trees are no exception.

Frost cracks are thought to occur when trees differentially heat up and cool down in winter.

This uneven cooling and heating sets up stress inside of trees and the result is a frost crack.

Heating and quick cooling can also cause the phenomenon of sun scald.

Sunscald and frost cracks normally occur on the south and south west sides of young trees.

In the winter the sun is at a low angle and shines on the bark of trees warming the surface as the day progresses. Large swings in temperature occur as the sun sets and the bark rapidly cools.

The stress caused by differential heating can cause the tree to split outright, as is the case with frost cracks or just damage the living cells in the cambium layer and result in sun scald . The cambium is a layer of growing and dividing cells just under the bark but above the hard wood of the tree. When the cambium is damaged the bark will crack and peel off leaving dead regions of trunk.

Once a frost crack occurs and the tree is split there is no chance it will rejoin and “heal”.

The crack itself allows fungi and other pathogens to enter in to the heartwood of the tree and can lead to decay. While this does lead to a reduction in strength it does not always lead to failure, immediately or in the near future. Trees with this condition can live for many years and be effective elements in a landscape. If the tree is close to structures or areas where people sit it should be inspected regularly and well maintained. The tree responds by trying to grow over the crack, however the growth itself pushes the crack wider. In the end the tree may fail prematurely but not unexpectedly if your Arborist has pointed this out.

Sun scald damages large areas of cambium in newly planted trees and they should be considered for replacement.

Wrapping newly planted trees with white paper and protecting the trunks of trees with understory plantings are two solutions that can be used for new plantings. Be sure to remove paper wrappings once the threat of frost has passed. Once trees are established you may not have to wrap them. Over pruning, or lifting of young trees will contribute to damage from the sun so use caution when removing the lower branches from young trees. If you have a planting project in mind or suspect you have sun scald or frost cracks contact you I.S.A. Certified Arborist.

I.S.A Certified Arborists are constantly updated on the latest planting and pruning methods backed up by scientific research on tree wound response.

Viburnum Leaf Beetle

If you find your viburnum’s leaves looking a bit odd this spring you may have problems with Viburnum Leaf Beetle, Pyrrahalta viburni.  This beetle was first discovered in North America in 1947 around Ontario’s Niagara region. It has since spread east and south to the Maritime Provinces and the North Eastern United States.  

This beetle larvae is most commonly found on native and imported viburnums including,

European cranberry, high bush cranberry, arrow wood viburnum, Rafinesque viburnum.

It will also feed on Sargent viburnum, wayfaringtree viburnum, nannyberry and blackhaw viburnum. Some resistant viburnum includes Korean spice, leather leaf, double file viburnum and several others.

Scouting for raised egg masses on the upper twigs in early spring can give you a jumpstart on controlling this pest.

The damage can be extensive, consisting mainly of leaf skeletonization by larvae and shot hole feeding by adults. Egg deposition on twigs by females may result in twig die back.

Significant defoliation may occur if the population is high and conditions are favorable. Repeated defoliation may result in plant mortality, and will certainly reduce utility in the landscape.

Viburnum Leaf Beetle produces one generation per year overwintering as eggs deposited on twigs by the females the previous year. Females can lay up to 500 eggs in a season before frost kills the adults.

Lavae emerge in May and feed gregariously on new foliage, skeletonizing leaves down to only the mid ribs. Larvae fall to the ground and pupate and emerge in July to feed on new foliage and create irregular holes in leaves. Adults are active, mating and feeding until the end of the season.

Removing egg masses by pruning is an effective cultural control, ladybugs will also feed on larvae and reduce numbers.

Chemical controls are effective in controlling larvae and adults. Applications should take place to coincide with larval emergence as well as a second application at adult emergence. Systemic insecticides are also effective in controlling both stages.

I.S.A Certified Arborists are industry recognized experts in plant insect and diseases control. Contact your I.S.A. Certified Arborist to see if you have this damaging plant pest.

Lessons from Sandy and Others

If you survived Sandy, Irene, Lee, or Ernesto, on TV or in real life you may have learned a few lessons of your own.

As a person who cares for trees daily, both in the practical and abstract sense, it was a tragic tutorial that I will not forget. I have to date not experienced the level of destruction to property nor do I expect to again. Personally we had a large oak tree slam an 80 year old masonry fire place into a pile of rubble. It was thankfully; a ways from the house and it can be rebuilt. Many people were not so lucky. I have also seen the ensuing panic that has no doubt resulted in many unnecessary tree removals in the name of safety. 

All trees are at risk of failing, I want to say that right up front. As long as there is gravity, wind and the weather this will continue to be a possibility.

We live with risk every day and the key is to look at it objectively and try to minimize it where possible.

The key to mitigating risk is knowledge and preparation.                  

Inadvertently I participated in an experiment that yielded surprisingly predictable results. A year and several months ago on October 29^th 2011, we experienced a heavy snow and ice storm that caused tremendous numbers of broken limbs. Over the next year, in several different operations, we removed the broken branches, reduced the numbers of branches, and cabled and supported all of the trees except one. That tree had a large bracket fungus halfway up its canopy where the two main trunks split into co-dominant leaders. Based on my observations that tree would have to eventually be removed.

While I was waiting for the appropriate time to remove the tree, Super Storm Sandy arrived and her 85 mph winds howled through the trees and across the rain soaked saturated soils. Not one of the trees that we had reduced the canopy, pruned broken branches from or installed preventative cables in failed. The trees that were pruned were of higher priority as they would have certainly caused damage to the house had they fallen on it.

The one tree we ignored popped out of the ground and fell like a gavel on our masonry fireplace, across the fence and into the garden.

There is a conceptual equation for accessing the potential risk presented by a tree in a landscape.

It is as follows: Risk = Potential x Environment x Target.

Risk increases if you have a potential for failure like, a weak crotch, overextended limb or cavity. If you have an environment that increases the possibility of failure like a newly exposed face or area that was previously sheltered, a wet site with shallow roots, or a change in grade due to construction. All of this means nothing if you don’t have a target like a structure or even children playground equipment. All of these elements are not created equally and it takes a trained professional to understand all the potential problems that create and reduce risk. ISA Certified Arborists have continuous training that helps them to keep up with the latest tree risk information.

Have you contacted your Arborist to review your changing landscape?