Archive for azalea pests

Designers List of Shade Plants for Root Weevil Resistance

NE Portland Hostas with Root Weevil Damage

Root weevil damage distracts from an otherwise beautiful collection of shade loving plants.  

Designers List of Shade Plants for Root Weevil Resistance

I wanted to write a blog about shade plants for root weevil resistance. Root weevil disfigure so many shade garden plants and can make a garden look ravaged. It’s disappointing to see hosta and other plant leaves looking all chewed up. Can we design a shade garden with beauty and style without using root weevil favorite snack plants?

“Well HELL that’s not much of a shade garden” is what I said when I thought about eliminating all the plants root weevil like to eat. I was disappointed in the tiny number of plants that would work and wandered off to write about something different, something a bit cheerier!!!! However, I’ve been thinking about it and yes, we have some great plants we can use. 

Evergreen Shrubs  

Fatsia japonica Spider's Web in SE Portland Residential Landscape Design

Sometimes choosing an interesting variegated leaf, such as this Fatsia japonica ‘Spider’s Web’ can hide the notching caused by Root Weevil (look close!)

Aucuba, Daphne and Fatsia are not root weevil favorites and if you select the variegated forms the notching doesn’t show as much. To be specific, Daphne odora ‘Marginata’,  Fatsia japonica ‘Spider’s Web’, and Aucuba japonica ‘ Gold Dust’ are varieties that I recommend.

I have never seen much leaf damage on our Native Huckleberry (Vaccinium ovatum) probably because the leaves are so tiny.  

Three Root Weevil Resistant Rhododendron for Part Shade 

Grant Park Garden Design Rhododendron with Root Weevil resistance

The fuzziness on the bottom of the leaves on some Rhododendrons reduce Root Weevil damage.

I’ve found the official lists less than helpful since most Rhododendron listed are sun lovers. Root weevil prefer part shade to shade. 

Rhododendron ‘Clipiense’ is my best weevil resistant compact rhododendron for shadier situations. This rhody has fine hairs on the leaves so root weevil rarely bother it. It’s a slower growing variety and can take more shade than the other two I have listed but not deep shade.

Rhododendron ‘Fred Peste’ is a compact red rhododendron.  Fred does well in morning sun and afternoon shade, although he can take more sun than average.  

Rhododendron ‘Blue Diamond’ can take full sun but does well in full am sun and afternoon shade. It can get taller than wide.

Perennials   

NW Portland Sword Fern and Hardy Geranium in Residential Landscape Design

Sword fern (Polystichum munitum) and Hardy Geranium (Geranium macrorrhizum) do not show Root Weevil damage.

Sword fern (Polystichum munitum)  has a fuzzy frond (leaf) and root weevil don’t eat fuzzy leaves typically. Most fuzzy fronded ferns will be root weevil resistant and are an important player in a root weevil free planting. 

Hellebore argutifolius is perfect for NW Portland Landscape Designs

Helleborus argutifolius photo credit: Great Plant Picks

Hellebores are typically safe from weevil once they are mature plants. When the soft and munchable new leaves unfurl in February the root weevil have not hatched yet (here in Portland) so are not present until late April or May. The harder leafed hellebores like Helleborus argutifolius seem particularly impervious. 

Groundcover Plants   

Oregon Oxalis (Oxalis oregana) doesn’t seem to get a lot of weevil attention in my gardens and it is fun to add to salads. Same with our native piggy back plant Tolmiea menziesii. It has hairy leaves and is great for shade. For Saxifraga varieties, use the hairy leaved varieties for weevil resistance, the smoother ones are on the weevil munch list. Hardy geranium varieties that smell like cedar and have a fuzzy leaf are 100% weevil resistant – Geranium macrorrhizum for deep to moderate shade and Geranium x cantabrigiense for part sun areas. Another good bet is Sweet woodruff (Galium odoratum)

Last but not least, Euphorbia Rob’s spurge (Euphorbia amygdaloides var. robbiae) is a tough evergreen ground covering shade plant. I consider it a thug but it’s great to use in gardens where I have a path that doubles as barrier to their creeping roots. This plants roots must be contained or it will march right over your hostas. I’ve never seen any root weevil damage on this plant.

 Know Thy Enemy?   

Root Weevil have no natural predator here in the Pacific Northwest so it’s rare to find a shade garden without them.  We can cut the population of root weevil down to tolerable numbers and thus get our beautiful shade garden back. Read my blog “Attack of the Root Weevils”  to learn what can be done to reduce their population in your garden. 

 

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!