Archive for Garden Pests

Natural Slug and Snail Control In Your Portland Landscape

California Brown Snail in Portland, OR

Slugs and snails do a lot of damage in Portland gardens.

Slugs and Snails in your Portland Landscape

My history with slugs in the garden

I was never thrilled with my options for dealing with slugs and snails.  In the 80’s we had the typical little gray French slugs and snails in our gardens and they were pesty enough.   I had often just hand picked them and kept the numbers down.  Then in the 90’s we started seeing California Brown Snail and they added significantly to the total damage.  It was too much for me to manage organically.  The beer bait didn’t work for my garden on a city sidewalk in NW Portland’s Nob Hill District.  Dogs would drink the beer which is NOT good for them and the traps looked tacky too. Using the snails for escargot doesn’t work as a pest management practice since the typical serving is six 1 ½” snails per person.  My family would  never go for Escargot anyway.  They are not adventurous diners.

 

Slug Bait Problems

NW Native banana slug does not damage living leaves

The banana slugs only eat leaves that are decaying or broken. They also pollinate native spring flowering plants on the forest floor. I did not like leading them to slaughter.

I started using the “pet safe” iron phosphate slug bait.  It was an easy method to cut down the population compared to beer baiting or hand picking them. The problem with slug bait is that it does not discriminate. It would lure innocent NW native banana slugs to their death along with the real culprits that did the damage to my plants.

Another problem with slug bait is it doesn’t protect your plants immediately.  Slug bait lures the slugs to the bait but does not kill them right away.  They have time to do a lot of damage before they sicken, stop feeding and then die.

Worms die from iron poisoning

The major issue is the iron phosphate remains in the slug’s body and breaks down and ends up in the soil.  This iron residue left behind in the soil created a toxic environment for worms, the creatures who keep our soil healthy.

I didn’t notice it myself until I got raised beds in my community garden.  I noticed a steady decline in the population of worms in my beds.

Copper wire around vegetable bed deters slugs

Daizzie inspecting the copper wire which keeps slugs out of my veggies by producing an electric shock.

 

There is an inert ingredient in the pet safe slug bait that combines with an active ingredient to kill earthworms.  They die from iron poisoning.  The combination was also causing harm to wildlife and to small domestic animals so it was time for me to make a big change.

Slug Bait Alternative-Natural Slug Control

Ann Lovejoy is a trusted resource and treasure for Pacific NW Gardeners.  She is the one that made the connection between the iron phosphate “pet safe” slug bait and the harm it was doing.   Read more about how slug bait kills worms. 

She made several suggestions for what to use instead of slug bait.  My favorite is using liquid caffeinated coffee sprayed onto plants as a repellent.  I tested it this past fall to great success.  I was able to protect my kale crop from slugs.  I purposely sprayed coffee on only half the plants as a test.  The plants I did not spray were missing half their foliage.  The plants I sprayed had no holes or missing foliage.   I sprayed at least once a week during the fall rains.  Ann says a direct spray of coffee will kill the slugs but I could not tell if this was a success.   I sprayed the coffee directly on slugs but when I came back the next day the sprayed slugs were no where to be seen.  They may have crawled off and quietly expired but I was not sure. Maybe my coffee wasn’t strong enough. I will do more testing now that the soil has warmed up enough for new slugs and snails to hatch. I’ll post again and share what strength of coffee it takes for an obvious demise.

I can’t wait to share this with my landscape design clients.  Many clients have pets.  The fact that pet safe slug bait is toxic needs to be shared.

Another option to deal with slugs in raised beds is to line the edge of the bed with copper.  I used a copper ground wire but you can use sticky copper tape available at most garden centers and it will last maybe one garden season if you are lucky.  It is easy to buy and apply to your raised beds, pottery and containers.

Slug or Snail?

What’s the difference between slugs and snails?  Slugs and snails are pretty much the same animals according to Robin Rosetta, Associate Professor at OSU.  Over time slugs evolved out of a hard shell so they could move through cramped spaces and allow them to get down into the soil to find food and protection.  Apparently, there is still sort of a shell under their hump like mantle.  Snails still have a shell and so are restricted to above ground activities.  They use their shells to survive inclement weather and are protected from some enemies and predators.

Bad News about Slug Bait and Winter Garden Care Tips

Slugs at NE Portland Landscape Design in a Day

Slugs on a Honeydew Melon Date

Winter is just around the corner here in Portland.   Here are 5 timely tips to help you care for your landscape right now.

Slugs Last chance to knock out slugs! Control your slug population now in late fall.  They lay thousands of eggs that will hatch in spring.  I’ve got bad news about using the so called pet safe slug baits. New science says it kills your earthworms and can sicken your pets and other animals.  Control your slugs with beer traps or even better an instant coffee spray.  Yup coffee! Fill a spray bottle with strong instant coffee or any coffee except de-caf.  Spray the leaves of plants they prefer and any slugs or snails you see.

I grow lots of winter greens here in NW Portland so I’ve been out there spraying down the leaves of my beautiful Dinosaur Kale plants to protect them now.  Spraying coffee once a week in fall and early winter makes a big difference in the spring hatch of slugs.   Read more about why slug bait harms worms.

Coffee bag

Its the caffeine that kills slugs or snails. Instant coffee works well.

Mulch.  If you only do one thing to improve your soil and care for your plants, mulching is the biggie.  Schedule your winter mulch application for the last week of November to mid-December or hire someone to blow in your mulch.  Companies such as Bark Blowers will blow in mulch including the newer “living” mulch products that I prefer.  One company that provides mulch inoculated with beneficial bacteria is Natures Needs, a product called  Recology Compost.  McFarlane Bark, Mt Scott Fuel and Grimms Fuel supply basic mulch products.   Did you mulch just 2 inches deep?  Great!  Now go and unbury the crowns of your plants so they don’t die from rot during our wet winter. Burying plants with mulch might be a good practice in Vermont or Montana but not here.

Iron gate design with snow

Landscape Design in a Day client’s custom gate.

Protect your plants from winter temperatures

The best cold protection for plants in the winter isn’t something that naturally occurs to most people.  Over watering and over fertilizing done in summer can cause plants to not go dormant.  When cold weather comes, they are not prepared.  Read more: Protecting Plants from Winter Cold Starts in Summer 

Pruning knowledge  There are many plants that should not be cut back in the fall and winter.  There are many perennials and grasses that can be cut back to create a more attractive winter landscape. This is a case by case basis which drives new gardeners crazy. Consider consulting with your garden designer who can teach you what to do to your plants and when.  It feels good when you know what to do.

Protect your pottery  The best winter protection for your pottery is proper drainage and location.  Make sure water drains through the pots hole and doesn’t back up.  If water sits in the bottom and it freezes, good bye pot.  I have had Vietnamese high fired pottery outside and intact for over 15 years.  I always put drainage material in the bottom of the pot and a piece of flagstone under the pot or I use those little pottery feet.

If I have expensive pots where they will get east winter wind, the kind of wind that freezes rain to ice on the power line, I would move them into a protected area for winter right now. I hate to even think about that kind of weather but we get our share here in Portland Oregon, especially in January.   Its hard to pay attention to the weather report, and besides who wants to move heavy pots around when its icy cold out?  Not me.

Birch Trees Going Going Gone

Birch trees going going gone

Another 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.

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.    Fast forward to today.  Boy was she right!!  It seems to me as I look back over these past years that the birches in the subdivisions died first.  Many developers, builders and home owners picked the Himalayan White Birch also called Jacquemontii, for its crisp white bark and over planted them.   In 2009 I was working with landscape design clients in a Vancouver neighborhood.  They had already had 2 birch trees removed and we made a replacement plan for the third as part of the Landscape Design in a Day.  Their neighborhood had already removed over 200 birches.  Their developer had used them extensively.  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.  Over time however the bronze borer changed its preferences and became attracted to the available and over planted Himalayan or White Birch.  It makes sense from an evolution perspective; why not change to fit the food that is available?  Smart bug!!!

Fixed up close view

Himalayan White Birch used to repel 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 with my clients so I am in every conceivable neighborhood.  The Bronze Birch Borer is now in North Portland to SE Portland, not just the suburbs.

These days when I have a client who has a healthy looking birch I give them the current research and bad news.  From what I have read there isn’t a whole lot of good news.   I often include in their design a potential replacement tree for when, not if, their tree is devastated by the Birch Bronze Borer.  It’s shocking and pretty sad for them to hear that they will probably witness the demise of their tree especially when it looks just fine.

th2_betula_heritage_3

Heritage River Birch in winter.

If you have a birch tree that is thriving consider starting to irrigate it if you haven’t already. You might start by deep watering it every two weeks. Under no circumstances should you water your tree every day – that is not helpful  (see my watering tips blog).   There are chemical protections that you can apply to your tree before it becomes infected that will typically keep it from getting the borer.  General Tree Service is one company who provides this  service.    Sometimes the tree can be saved  if you can catch the infestation at the very beginning but you will need to apply the pesticide every year.  Another important issue to think about it this:  The product is a systemic pesticide.  Many people refuse to use any systemic pesticide because some can kill honey bees.  Birch trees are wind pollinated not bee pollinated and so the systemic should not theoretically affect honeybees.   If you have flowering plants of any kind under or near the birch those plants will uptake the pesticide and that can harm bees.  This protection for your birch is contrary to protecting bees.  I guess you could take out your hostas or other flowering plants and put in sword ferns.  In short, if you love your tree, start taking care of it.  The first trees that died seem to me to have been neglected trees in full sun and in areas where there were too many birch trees so the borers could move from one tree to the next door neighbors tree.

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

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

What to look for:  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 but remember last years horrid, hot and nasty summer?  There were trees who seemed to get the borer early and by the end of the summer, the trees were gone.   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 hole, a sort of reddish liquid which looks as bad as it sounds………Is my tree bleeding?  So this is not a happy blog but there are some great trees to consider for replacement.

th2_cercidiphyllum_japonicum

Katsura tree with beautiful fall color.

New resistant varieties;   I am hesitant to trust that new resistant white barked birch varieties will stay resistant since the Jacquemontii/Himalayan did not stay resistant.  When I have a client who loves birch trees 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 and since it is not related to birch I am not worried about Borers.  I know that the trees I place in a home landscape may be removed for capricious reasons by the next homeowners but selecting trees that have the best chance of becoming mature old specimens in their neighborhood is my chance to contribute not only to my clients well being but for my city and region.  Keeping up to date up on the best trees to use and keeping my selection diverse will make the best urban forest for the future.

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.

White birch trees that have been planted in part shade, in good soil that drains well and that get irrigation may continue to survive.  Another bit of advice from Kym Pokorny’s article is to mulch over the shallow roots of your birch tree.  This provides some protection from heat and also from physically damaging the surface roots.  I’ve been told by an arborist in the past not to put more than 2 inches of mulch over  roots.  The best person to ask about these fine points of tree care is an ISA Certified Arborist.

Katsura 'Red Fox' has unique red foliage.

Katsura ‘Red Fox’ has unique red foliage.

I came across a lovely 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 doesn’t seem to be infected.  Some birch trees that are individuals, seed propagated instead of cutting, may have some unique genetic protection and so we can only hope that some of these individual trees will remain to grace our landscapes and homes.

 

 

 

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.