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Archive for Garden Pests – Page 2

Protecting Our Portland Birch Trees from Bronze Birch Borer

Protecting Our Portland Birch Trees from Bronze Birch Borer

 NE Portland birch tree marked for removal by the City of Portland due to bronze birch borer.

Birch trees marked for removal by the City of Portland due to bronze birch borer.

Birch Trees Dying from Bronze Birch Borer

Many developers, builders and home owners picked the Himalayan White Birch (also called Jacquemontii,) for its crisply white bark and over planted them. They even planted them in parking strips with no irrigation, in full hot sun, which is not a good place for a birch. My Vancouver client’s neighborhood had over 200 mature infected trees removed. They had already lost 2 birch trees and I made tree replacement suggestions as part of their Landscape Design in a Day.

Back in the 1980’s the Himalayan White Birch was touted as the new success story because it had been hybridized to repel the Bronze Birch Borer (BBB). At that time I was a student learning about trees at a local community college. The European Weeping White Birch had been decimated by the BBB so everyone was very excited about the new Himalayan White Birch. Over the next 20 years, the bronze borer changed its preferences and became attracted to the over planted Himalayan White Birch. It makes sense from an evolution perspective; why not change to fit the food that is available?  Smart bug!!!

City of Portland has tagged this borer damaged birch tree for removal

30 years ago Himalayan White Birch was used because it repelled Bronze birch borer.

Recently I have noticed the dreaded yellow tape of death tied around birch trees in the city. I create my Landscape Design in a Day drawings on site so I am in every conceivable neighborhood.  The Bronze Birch Borer is now all over Portland and has spread south to Klamath Falls.

Today when I see my client has a birch tree, I give them the current research and it’s mostly bad news. I often include in their design a potential replacement tree for when, not if, their tree is devastated by the Birch Bronze Borer.

River Birch (Betulus Nigra) is a safe replacement tree - Bronze birch borer does not feed on this birch tree.

Heritage River Birch in winter. River Birch (Betulus Nigra) is a safe replacement tree – Bronze birch borer does not feed on this birch tree.

Protecting Your Portland Birch Tree

My research says watering your trees regularly before they are infected is a huge step toward preventing the disease. If you have a birch tree that is thriving or only has minimal borer damage, consider starting to irrigate it ASAP. Start by deep watering it every week to two weeks starting in early summer into mid to late fall.  Don’t let your tree get stressed. (Deep water is a long slow soak with your hose.) Under no circumstances should you water your tree every day – that is not helpful.  (See my watering tips blog).

Pesticide treatments

I’m also reading that more people are using a chemical treatment (which will help your tree) than they were initially. I’m not very happy about that because the treatments will harm bees. They are mostly drenches that are systemics (bad for bees) or injections done by tree services which are also systemic in nature (and so bad for bees). Apparently the timing of the treatment and how it is done can make it less lethal to bees but isn’t this backward of  saving the bees and therefore our food supply? If it were my tree, given my very strong feelings about protecting bees, I would try watering deeply and regularly and not treat the tree with pesticides. If the tree is too far gone I would have it removed, grieve and plant a new tree that is resistant to disease and insects and prefers little summer water.

Weeping Katsura tree has similar texture to Birch

Katsura tree at Lan Su Chinese Garden in Portland, Oregon

In short, if you love your tree, start taking care of it. The first trees that died were neglected, poorly sited and in neighborhoods chock full of white barked birch trees.

Weeping Katsura is my go to birch replacement now since borers have killed so many birches.

Weeping Katsura in one of my clients gardens in Willamette Heights.

Signs of Bronze Birch Borer

The first signs are yellowing foliage in the top of the tree. As the insect infestation continues, small branches and tips die. It moves on into the larger branches. Declining to the point of death usually takes several years. There are other signs of borer; ridges in a lightning pattern and a distinctive D shaped hole in the bark. There can be a kind of stain coming from the holes, a sort of reddish liquid which looks as bad as it sounds.

Cercidiphyllum_japonicum, Katsura tree

Katsura tree with beautiful fall color.

New Resistant Varieties-Maybe

I am hesitant to trust that new resistant white barked birch varieties will stay resistant if we over plant them as we did the Jacquemontii/Himalayan white birch.  I offer the river birch which has a brown peeling  bark and typical birch leaves.  Alternatively my favorite replacement for birch trees is the Katsura tree also called Cercidiphyllum. The Katsura has the graceful shape somewhat reminiscent of a birch tree with heart shaped leaves that flutter in the breeze.  I feel it is a safer choice since it is not related to birch at all but alas no white bark!

Selecting trees that have the best chance to become mature old trees is my way to contribute to my clients and our community. Keeping up to date on the best trees to use and keeping my selection diverse will make the best urban forest for the future.

Kym Pokorny, (now writing for OSU’s Extension Service),  says these are good replacement choices;  ‘Heritage’ river birch (Betula nigra ‘Heritage’) and ‘Whitespire Senior’ gray birch (Betula populifolia ‘Whitespire Senior,’ which has the whitest bark of the replacement tree ideas.  I suspect if we over plant these borer resistant birch trees, the borer will change its tastes to the available food so the best thing to do is plant lots of different trees.

Katsura 'Red Fox' is a smaller tree that is getting used in irrigated parking strips.

Katsura ‘Red Fox’ is a smaller tree that is getting used in irrigated parking strips.

I came across a lovely old white birch tree just the other day in the Buckman neighborhood and gave my new client, who had just purchased the home, some information on how to care for the tree. The tree seems untouched by borer and is situated where it gets some afternoon shade.  He will start to summer irrigate.  Perhaps some birch trees are unique individuals because they were grown from seed and this unique genetic combo may cause them to be unattractive to the BBB. We can only hope that some of these remaining individual trees, if irrigated, will remain to grace our landscapes and homes.  In 2010 Kym Pokorny, my favorite garden writer, warned that our graceful white bark birch trees might become a tree of the past in Portland. Boy was she right!!



Lace Bug Update

Azalea Lace Bug damageLast year I wrote a blog about a serious new insect problem for landscapes in the Pacific Northwest. It was serious because rhododendrons and azaleas make up a large percentage of the plants in most gardeners landscape. The easy way to control the insect was with a systemic pesticide that harms bees.  Many people were talking about removing all their susceptible plants rather than harm bees.

Here’s my latest report and what you can do to save your plants without killing bees:

Save bees and your azaleas and rhododendrons. How big a problem?
I have visited over thirty client landscapes in the Portland area since February – all the gardens but two had moderate to severe lace bug damage on rhodies and azaleas.  I was already expecting the 2015 lace bug plant damage to be a huge problem for my clients. Robin Rosetta, Associate Professor, Extension Entomologist, OSU says the lace bug hatch is a full month early.  This is very bad news unless you are prepared to start treating your plants now in mid-to-late April and early May.

Lace bug eggs waiting to hatch.  Photo by Robin Rosetta.

Lace bug eggs waiting to hatch. Photo by Robin Rosetta.

Strong blasts of water should be applied to the back of the leaves to damage the wings of the lace bug while it is in its soft nymph stage.  It can be a little difficult to hold your leaves steady to spray the back side, especially if it is a large rhododendron.  Portland Nursery has something called a Bug Blaster Head for your hose.  It’s easier to use and has a safer pressure for your plants’ leaves.  It also has a wand attachment that would make it possible to treat a large rhododendron.

Insecticidal soaps applied to the back of the leaves will also damage the lace bug nymph. These two methods are effective only while the nymph is soft.  Once it turns into an adult, soaps won’t work and water spray will not remove embedded eggs.

Green-Lacewing March Biological

Green-Lacewing March Biological

This may get confusing because the bad bugs that damage your plants are called lace bugs.  I’m about to introduce you to a good bug that eats the bad bug. The good bugs are called green lace wings.  If you don’t want to spray your plants because they are too big, there are too many plants or you want to work toward a long term solution; you need to purchase green lace wing larvae from March Biological  or go to Portland Nursery to order through them.  The green lace wing will eat the newly hatched lace bug and prevent the lace bug population from exploding.  Getting green lace wings in a high population in your garden will help with the next one or two lace bug hatchings that we expect this year.  My friend, Phil Thornburg, from Winterbloom has successfully diminished his damaging lace bug population. It took him a couple of years but he did it by applying green lace wings instead of pesticides.

Plants in full sun seem to be the most damaged from lace bug.
Basically they are stealing the green right out of the plants’ leaves and laying eggs that will hatch in another month adding insult to your already damaged plant.  Remember to water your rhododendron and azaleas regularly this summer –  they will need the extra support.

Question: What does lace bug on my rhododendrons have to do with bee colony collapse disorder?

Rhody Lutea March 2015 treated with bee killing spray

Rhododendron ‘Lutea’ in my client’s garden without any damage.  A rare occurrence.

Answer:  Systemic drenches often contain imidacloprid. It’s popular because it’s easy, the chemical is suppose to be safer for mammals (so humans, rats, bats are pretty safe) but the spray will harm or kill bees or any insects who feed on the plant.  For months afterwards bees take it back to the hive with the pollen so it’s not just harming one bee – it’s harming the colony.

The time to treat your plants without harming the bees is now!


Lace Bugs on the Move in Oregon

Azalea lace bug is a new pest that has decided rhododendrons are on the menu as
well as azaleas. This seems like a big problem because azalea lace bug has multiple
hatchings in a season and can do a lot of damage. The old rhododendron lace bug only hatched once a year in the Pacific Northwest.

Azalea Lace Bug damage

Rhododendron leaves showing damage from azalea lace bug

Organic Control Methods

Systemic sprays and insecticides kill bees. It’s very important to use methods that don’t harm beneficial insects.  Since drought and sun stressed plants are more susceptible, one method is to give these plants better care.  Practically speaking, I would say irrigate even your old rhododendron trees that never seem to need  a drop. Water them once a week during hot summer days as a preventative measure. Preventative methods are best.  So far this spring, out of perhaps 60 gardens, I’ve only seen one garden that didn’t have these new pests.  Preventative methods I’m recommending are building up green lace wings in your garden preferably before you have the pest or when you see that you do have it and better watering.

Using green lace wings, a beneficial insect, is another effective way to combat lace bug.  You can purchase green lace wing larvae and apply them near your affected rhododendron, the idea is to build a population of green lace wings in your garden from March Biological in Sherwood, Oregon. Ladybug Indoor Gardens in Medford, Oregon can also be reached at: 541-618-4459541-618-4459.  Please note, green lace wings are pretty, they remind me of Tinker Bell, sort of.  Using the green lace wings does work, as my associate and friend Phil Thornburg, (Winterbloom) can attest.  It took about 3 years but his plants have fully recovered and he has a nice population of the lovely green lace wings in his gardens as a bonus.  Their latin name is Chrysopididae and you can look them up on Wikipedia for more details.

OSU Azalea Lacebug PDF file imageThe chemical sprays I have seen recommended for lace bug are harmful to beneficials such as honeybees.  My recommendations are purchase and apply green lace wings and irrigate azaleas and rhododendrons weekly in the summer.   This will allow us to wait until a honeybee friendly solution to help us protect our plants is found.

Azalea lace bugs are here to stay.

For more details, download the informative Oregon State University flyer.

Treatment for Blackberry and Ivy – How To Get Rid Of It

Garden Tips for getting rid of Plant Invaders

The best time of year to treat blackberries and English ivy is coming right up… prepare now!

Blackberry Fruit

How can anything so sweet, be so evil?

Plan to treat invasive blackberry in September and early October. The reason for the specific timing is this: only in the fall will the plants pull an herbicide to the roots, thereby killing the entire plant. The rest of the year treatments are only partially effective. For greener garden practices that use less chemicals treat the plants only in the fall, and water your bad old blackberries well prior to treatment. In fact you could even fertilize them and pamper them for about two weeks…….and then treat them with an herbicide.

My long time client Pat Tangeman  is clearing a large area of her property. She bulldozed last winter and got rid of a decades old blackberry wilderness that had an extensive root system with many large stumps. However, even a bulldozer didn’t kill all the blackberries! Many came back this spring so she called me to problem solve and design a planting plan for the area.

The result:
This fall she will treat her remaining blackberries and will allow the herbicide to trans-locate to the roots to truly kill the plant. Then she will have the remainder of large roots dug out. Once this is done she can plant the new garden we designed together. Victory over the blackberry!

Another client in the Dunthorpe area is having her English ivy treated by professionals the first of September. She is utilizing the same techniques by doing the pre-watering and pampering herself. Once the invasive plants are dead we will be ready to place her new garden plants from her garden planting plan.

Not sure still when would be a good time? Need a professional hands on approach to help get you started? There are still a few appointments for Garden Coaching open in September and October. Winter is also a great time for making plans so you can have what you want instead of taking your precious time to care for a layout and plants you don’t like.

Attack of the Root Weevils in Portland Shade Gardens

Why you should care about root weevils, and what to do about them once you do.

Many Portland established shade gardens have  leaf damage from adult root weevils (see photo showing leaf notching). It is ugly, but it doesn’t kill your plant. A lot of leaf notching can spoil the looks of the plant just when you wanted to enjoy its beauty. The serious problem is caused by their larvae who eat the roots of your plants during the late fall and winter. It is very difficult to kill the larvae because they live underground nestled into the roots of your plants to be close to their chosen food source. Think of them as tiny, tiny zombies! Rooooooooooooooootttttssssssssssssss………..

So how do you know if you have a root weevil problem? Here is what I recommend:

Root weevil damage on hydrangea in Portland landscape design

It’s the damage done to the roots that we worry about. We must control the adult weevil before she lays her eggs.

Check your indicator shrubs for notching! These are Hydrangea, Red Twig Dogwood, Azalea, and Rhododendrons. Many perennials will also show the notched leaves such as Hostas and Coral Bells (Heuchera).  If you have only a few notches, you don’t have to do anything or you could treat once a year as a preventative measure.  If you have more than a few notches, we need to talk but you can also check out my other root weevil blog for all the gory details of killing root weevils.  It is tricky to do.

Don’t bring them into your garden………Here is a timely tip, be very picky about buying plants on discount, or at fundraisers!  Look for notching on the leaves, and don’t buy any plant that has notching, or is near plants with notching.  Root weevil can walk over to the plants near by and lay eggs so even if there is no notching on a plant there are probably eggs in the potting soil.  You don’t want to introduce them into your garden. (I’m not saying they came from your freshly purchased potting soil….root weevil just walk from one plant to another and lay their eggs.)

Now the important part. How do you get rid of them?  Hand picking is the easiest to actually do but they can be very hard to spot.  This dull colored beetle is only 1/4″ and hides effectively in the top of the soil or inside a leaf crevice. It can take checking your plants several evenings a week with a flashlight to find even one.

The chemical products out there are harmful to you and the bees which we need in order to have food. Using chemicals to get rid of root weevils is definitively not the way to go.

I purchase living nematodes that are specifically listed for root weevil. Properly applied, they will swim through your soil, enter the body of the root weevil larvae, and lay their eggs. The nematode hatchlings will eat the larvae. Initially you will do this in both September /early October and the following May which are the ideal nematode vs. larvae times!

The 3 most important things:

The soil must be warmed up and moist

You must apply the nematodes at dusk, never in direct sunlight.

Get the timing right-treat in May or early June.  Treat again in September.  If we are having a cool May you may want to wait until June.  In September you want to be sure your soil is well watered prior to the treatment of nematodes, and then water well for two weeks following the treatment. This will eliminate some of the root weevil problem for the next year.  You will have to repeat the biannual treatments for a few years to get the weevils properly controlled, and then continue with a once a year preventative treatment cycle (in September).

You’ll get better results if you use Pondzyme in the water before you add the nematodes.

The good news is that it is really easy to do…ok it’s tedious but your shade garden can look so bad if root weevils become numerous.
1) Take a 5 gallon bucket and fill it up with water.
2) Treat the water with a product called pondzyme (people use it to protect their fish from the additives in our water). I use 1 and ¼ teaspoons of Pondzyme to 5 gallons of water.
3) Add the nematodes to the water.
4) Using a plastic pitcher, not metal, I then water the nematodes into the soil where I see leaf notching.
It is very little effort for a dramatic and healthy result.   Good gardening!


March Biological is mail order.  I like them.
Living nematodes for root weevil larvae can often be purchased May through September at: Portland Nursery
Farmington Gardens
Cornell Farms
and other higher end garden centers.
Tranquility Ponds has 3 locations and they sell an 8 oz bottle of Pondzyme for $26.00.  Remember you need the pondzyme to protect your nematode warriors from chemicals in our water so don’t skip this step.  It is very concentrated so it should last you a very long time.