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.

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!

 

Attack of the Root Weevils

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

I have noticed that most established shade gardens have visible leaf damage  from adult root weevils (see photo showing leaf notching). It is ugly, but it doesn’t kill your plant. 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:

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 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. That means there are probably eggs in the potting soil that will hatch in your garden. You don’t want to introduce them into your garden.

Now the important part. How do you get rid of them?

The easy answer is, in the long term, the harsher one. The chemical products out there are either harmful to you or harmful to the bees which we need to keep our gardens productive and beautiful. Using chemicals to get rid of root weevils is definitively not the way to go.

I purchase living nemotodes 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 nemotode hatchlings will eat the larvae. Initially you will do this in both September /early October and the following May which are the ideal nemotode vs. larvae times!

The two  most important things ares that the soil must be warmed up and moist and you must apply the nemotodes must be applied at dusk, never in direct sunlight.   If we are having a cool May you may want to wait until June or call me and ask. In September you want to be sure your soil is well watered prior to the treatment of nemotodes, and then water well for two weeks following the treatment. This will eliminate some of the root weevil problem for 2013. 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 (still in September OR May).

The good news is that it is really easy to do!
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 nemotodes to the water.
4. Using a plastic pitcher I then water the nemotodes into the soil where I see leaf notching.
It is very little effort for a dramatic and healthy result.   Good gardening!

Resources:
Living nemotodes for root weevil larvae can be purchased now through September at: Portland Nursery
http://www.portlandnursery.com/
Farmington Gardens
http://www.farmingtongardens.com/
Cornell Farms
http://www.cornellfarms.com/
and other higher end garden centers.
Tranquilty Ponds has 3 locations and they sell an 8 oz bottle of Pondzyme for $26.00.  Remember you need the pondzyme to protect your nemotode 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.    http://portlandpondsupplies.com/