Will this cold snap help keep insect pests down, next season?

It's a beautiful, spring-like day today in Corvallis ~ a welcome relief from our recent spate of freezing weather!  Being half-Filipino and half-Italian, I have a propensity for sunlight etched into my genetic code.  But, I took solace in this recent round of cold weather, by imagining freeze-induced die-offs of key insect pests, in epic proportions.  

How might this current cold snap be wreaking mass entomo-cide on some of my most challenging garden pests? It likely varies across insects.

Azalea Lace Bug (ALB):  I couldn't find any data on the cold tolerance of ALB, other than secondary citations that the bug is hardy to cold weather.  The original publication is Neil, JW. 1985.  Pest-free azaleas can be a reality. J. Azalea Soc. Am. 7: 25-29, but I can't get my hands on that publication.  From the title and the journal, it seems that it would be an anecdotal report that ALB can survive extended periods of cold weather.  This isn't a surprise, since the insect overwinters in the egg stage, the egg is layed INSIDE leaf tissue (offering the eggs protection from cold, predators and parasitoids), and that the egg is covered by an adhesive goo that further provides protection from cold and natural enemies.  It's unfortunate, but this cold snap is unlikely to put a huge dent in ALB populations that we might see next season.

Azalea lace bug adults are about 1/4 of an inch from head to tip.  Start scouting your rhododendrons and azaleas for the first generation of young nymphs, as early as mid-April.  The first clutch of eggs generally hatches in early May, but could be earlier or later, depending upon local weather and other environmental conditions.  Photo Credit:  Robin Rosetta.  OSU Department of Horticulture and North Willamette Research and Extension Center.

If you want to see whether or not your rhododendrons or azaleas have overwintering eggs in them, you can scout your plants anytime between now and the April.  Look for signs of egg-laying damage, on the underside of the leaf, along the mid-rib.  The eggs are super-tiny, but are covered with a tiny brown speck (the adhesive I mentioned, earlier).  Robin Rosetta's fact sheet on ALB has a magnified photo of the eggs.  If you see signs of eggs in your rhodies or your azaleas, mentally or physically make note of which shrubs carry ALB.  Make sure to monitor those shrubs for the first generation egg hatch, anytime from mid-April to mid-May.  One of the best things you can do for season long control is to knock back that first generation of nymphs, so that they don't become adults who will lay more eggs in your rhodies.

Chemical controls are available, but some people have tried to use strong jets of water to knock the nymphs off of the plants.  Whether you use an insecticide or jets of water,  it's important that your shrub canopy is 'open' enough so that your control measure actually reaches the nymphs.  The nymphs feed on the underside of leaves, and in dense rhodie canopies, you will have a harder time reaching the nymphs with an insecticide or a jet of water, compared to a more open canopy.

If that first generation gets past you, ALB will be much more difficult to control.  The bugs are long-lived (by insect standards), and as time passes, you'll start to see an overlap of generations (egg stage, nymphs, adults all occurring together on the same plant).  Control measures, such as chemical controls or streams of water, will help control the nymphs ~ but will be less effective against other life stages, particularly the egg stage.  Keep in mind that chemical controls will also negatively impact natural enemies, such as lacewings, predaceous bugs, spiders and parasitoids ~ all of which have been shown to help naturally suppress ALB populations.

For long term control of ALB, make sure your rhodies are part of a diverse landscape.  Tree canopy cover and other shrubs will help promote spiders ~ one of the main natural enemies of ALB.  Annual wildflowers will provide nectar for green lacewings, which have been shown to help control ALB at a rate of 10 lacewing larvae per shrub.


Brown Marmorated Stink Bug (BMSB):  BMSB are often reported as 'nuisance pests' because they can aggregate in large numbers in your house.  In fact, National Wildlife Federation Senior Scientist Doug Inkley tracked the movement of BMSB into his house, and up to the attic in 2011.  Over the course of 72 days, Dr. Inkley counted 20,116 BMSB in his house!!  You can see from the graph, below, that there was a progressive movement up and into the attic.  Because BMSB overwinters in protected structures ~ like your house ~ this cold snap is unlikely to result in massive die-offs of this insect.

Dr. Doug Inkley tracked the movement of BMSB into his house and up into his attic over the course of 72 days.  Image source: http://www.nwf.org/Wildlife/Threats-to-Wildlife/Invasive-Species/Stink-Bugs.aspx.

In addition to being 'nuisance pests' in your house, BMSB can also be a real problem for gardeners.  BMSB use their piercing-sucking mouthparts to probe fruits and seeds.  They can damage pea pods, berries and stone fruits in the garden.  Unfortunately, for home gardeners, there aren't a lot of control options.  Biological controls aren't generally successful, because BMSB have a noxious scent that make them unappetizing to many predators.  Chemical controls are available for this pest, but at best ~ these options provide 'temporary relief' rather than long term suppression.  From our friends back east, we've learned that you just kind of learn to live with BMSB.  It becomes a 'new normal' in the garden.

Brown Marmorated Stink Bug Adults survive the winter by hiding out in attics, barns and other protected structures.  Photo Source:  Brown Marmorated Stink Bug website, OSU Department of Horticulture

Spotted Wing Drosophila (SWD):  We're still not sure how SWD overwinters.  On a sunny, winter's day, you can catch SWD in monitoring traps.  This suggests that the fly overwinters as an adult ~ but it is also quite possible that other stages are present in the winter.  In any case, the fact that we can find SWD in the adult stage, in the winter, bodes well for a massive freeze-induced die off of this berry-feeding fly.
In fact, there was a recent paper published by Danny Dalton (OSU) and colleagues, on the cold-tolerance of SWD, and how adults and pupa react to a 7-day 'freeze' event (Dalton et al., 2011).  And, their data suggests that these generally low winter temperatures, and the recent Willamette Valley, OR 'freeze' event bode well for SWD control.

If SWD are kept in conditions below 50 degrees F for about 30 days, they are super-susceptible to a cold snap.  However, if SWD are kept in conditions above 50 degrees, there are at least some adults that may survive a harsh cold snap, such as the one we've just had.

To see if we've been above or below the 50 degree threshold, I plotted the weather history for Covallis, Oregon over the last month or so ~ and marked on the plot where the threshold is for the 50+ degree F 'safe zone' and the below XX degree F 'freeze zone'.   And it looks like we have plenty of days where the mean temperature was below the 50+ degree 'safe zone', preceding our 7 day 'freeze zone' temperatures.  All of this suggests that this recent weather will help gardeners and growers with Spotted Wing Drosophila populations next season ~ a welcome relief for berry growers and berry lovers across Oregon.

Of course, it's important to point out that the Dalton et al., (2011) experiment was conducted in laboratory growth chambers, with very little organic material that the flies could use as shelter from the cold.  In 'the real world', the flies probably have many more opportunities hunker down from the cold ~ and thus probably have a greater buffer from the cold than my graph might suggest. 

Biodiverse Gardens are More Pleasing to the Eye

Despite publishing a scientific paper entitled 'Small scale additions of native plants fail to increase beneficial insect richness in urban gardens', I really am a huge fan and proponent of native plants and biodiverse gardens.  I just have a sense that the benefits of native plants (especially smaller shrubs and annuals) are oversold to home gardeners.  Not all native plants will use less water, better resist pests, or best attract wildlife.  And, gardeners are often left with the impression that they can install a few native plants to support local wildlife.  However, our results suggest that additions of 200-250 plants would be needed, to increase bee, butterfly or beneficial wasp richness by one species.

Given that a few plants won't yield strong benefits to native biodiversity, what type of gardening approach can help conserve wildlife?

A new paper by Petra Lindemann-Matthies and Thomas Marty (Does ecological gardening increase species richness and aesthetic quality of a garden.  Biological Conservation Volume 159,March 2013, pp 37-44) provides strong evidence that a whole gardening approach gets results.

They surveyed 36 gardens in Zurich, Switzerland, and scored them for the presence or absence of the following ecological features: 

• ponds (provide habitat for amphibians, aquatic insects, aquatic plants)
• flower meadows (provide nectar and pollen to a variety of beneficial insects, and host rodents that are food for birds)
• dry walls (provide nesting sites for beneficial insects, or insects that birds feed upon)
• nettle plots (provide nectar and pollen to a variety of beneficial insects)
• nesting sites for wild bees and birds
• decomposing piles of wood (provide habitat and nesting sites for a variety of beneficial insects)

and the following gardening practices:

• frequency of lawn mowing
• use of synthetic fertilizers
• use of pesticides
• frequency of weeding

A 'bee barn' at the Marion Garden in Salem, OR.

Beneficial Insect Garden at the Marion Garden ~ a demonstration garden of the Marion County Master Gardeners.

They created an 'ecological gardening' score for each garden, by assigning a '1' to beneficial practices (e.g. rarely or never using pesticides) and a 0 to non-beneficial practices (regular use of pesticides).  They then counted the number of plant, fungal and animal species within each garden.

Here is the good news!  Gardens with a higher 'ecological score' were more biodiverse, took less time to manage, and were judged more aesthetically pleasing by neighbors, compared to gardens with a lower 'ecological score'.

In fact, 67% of the variation in biodiversity among gardens was a result of the 'ecological gardening score'.  Only 35% of the variation in aesthetics was a function of the ecological score of each garden, which suggests that ecologically-friendly gardening practices have more of a positive impact on biodiversity, than on aesthetics.

You can learn more about ecological gardening practices by visiting Linda McMahan's ecogardening website, or by visiting an OSU Extension Master Gardener demonstration garden.  Locate the garden nearest you by visiting our Google Map of OSU Extension Master Gardener activities.

View OSU Extension Master Gardener Map in a larger map

Backyard Biodiversity ~ What's in Your Garden?

While researching potential speakers for the annual Gardener's Mini-College, I came across this lovely article in the New York Times, written by Carol Kaesuk Yoon.  I knew Carol from my time as a graduate student in the Entomology Department at the University of Maryland.  Carol's husband, Merrill Peterson (who is mentioned in the New York Times article), was a post-doctoral researcher in Bob Denno's laboratory, where I was working on my graduate degrees.

My time at Maryland was about as utopian as a graduate student's experience could be.  Our lab was fun!  Our field sites were a 3 hour drive from the University, and we often killed time by playing games where we took turns naming as many birds species, butterfly host plants, car models, cartoon shows, or anything else we could come up with.  If you couldn't think of something new to add to the growing list, you were out.  [File under: games nerds play.]

We also spent quite a bit of time talking about our various collections.  If you're an entomologist, it's nearly mandatory that you have a collection.  Bob and Merrill collected butterflies.  Merrill and Micky Eubanks kept birding lists.  Bob also collected:  coins, pine cones, lichens.  I really looked up to these smart and accomplished folks, and I wanted to emulate them.

So I started my own collection.

I collect cerambycid (longhorn) beetles.  Cerambycids are beautiful, and sometimes quite damaging.

A banded alder borer ~ one type of cerambycid beetle.  Image credit:  Larry Hanks.  Image linked to Science Daily press release at:  http://www.sciencedaily.com/releases/2008/08/080805153826.htm.

But once I bought my first house and started gardening, I also started to collect the insect species that visit my yard.  I don't collect every day, or even every week during the summer.  Basically, I collect on summer days when work gets overwhelmingly stressful ~ and I need to do something to calm my mind, but could still qualify as 'work'.

The bounty from an afternoon spent collecting insects in my backyard.

My secret goal is to document every insect species that visits my backyard garden, similar to the classic A Natural History of New York, by John Kieran.  I want to know what insects are mere transients through my garden, and which ones call my garden home.  I want to know which flowers the bees visit and which ones are merely eye-candy for me.  I want to see which ground beetles and springtails gather in my compost pile.  I'm curious to know if any insects dare tunnel through the hard, clay areas of unamended soil.

So far, I've collected 36 species of bee, 20 species of beetle, 29 species of fly, as well as springtails, snakeflies, mantids, and many other insect goodies.  It's amazing to me how hospitable a small patch of land can be, to so many different types of insects. 

Carol and her family are doing the same thing, although on a broader taxonomic scale.  And it all started with Carol's discovery of a rare moth on her Bellingham, WA windowsill ~ a moth that had, until that time, yet to be discovered (or at least, not recorded) in North America.  It made the Peterson - Yoon clan wonder what else might be discovered in their yard.  They thus set out to record every species they could catalog in their house and from their yard ~ efforts so elegantly reported by Carol in her New York Times article.

My own research has yielded a series of papers, co-authored with Kevin Matteson, Evelyn Fetridge and others, and suggests a few basic principles for insect biodiversity in gardens.

1. Gardens, even in the most heavily urbanized areas, host a diverse assemblage of beneficial insects.  (Fetridge et al., 2008; Matteson et al., 2008)
2. Plant more flowering plants, and you'll get more bees and butterflies.  The number of flowering plants in urban gardens predicted bee and butterfly diversity more than any other factor we measured. (Matteson and Langellotto, 2010).
3. Adding in native plants surely has benefits for wildlife (an argument convincingly made by Doug Tallamy in his book, Bringing Nature Home).  However, the small scale efforts often promoted by various organizations don't seem to have much of an effect, in terms of increasing beneficial insect diversity in gardens.  (Matteson and Langellotto, 2011). 

And, although I did not specifically research this principle, it should go without saying that if you want a diversity of insects in your backyard, you need to reduce or eliminate pesticide use ~ and in particular, reduce or eliminate use of broad spectrum insecticides.

In 20 or 30 years from now, it is my dream to publish a definitive list of the insects found in a single Oregon garden ~ all in an effort to show that gardens, if managed sustainably, really do offer promise as conservatories of insect biodiversity.

Garden Insects to Soothe a Stressed Out Soul

When life gets stressful, I go to the garden.  While finding a garden full of insects might further stress some, realizing the my garden is hospitable to all kinds of insects makes me feel better.

I photograph and catalog garden insects the same way that avid birders keep a life list.  Finding a new or unknown (to me) species always lifts my spirits. 

I use my iPhone, plus an insect loupe, to take close up photos of garden insects.  This is my poor (in finances and final product) attempt at nature photography.  But, it does the trick just fine for my purposes.

I place this magnifying loupe over the slot of my iPhone camera, to take close ups of insects in the garden.

Here are a few that I was able to find and photograph this evening.

Froghopper on the underside of a Rhododendron leaf.

Unidentified moth on Hydrangea 'limelight'.

Unidentified bug on Hydrangea 'limelight'.

Unidentified moth on Hydrangea 'limelight'.

Lygus elegans on Hydrangea 'limelight'.

Lygus elegans on Zinnia elegans.

Lygus damage on my zinnia petals ~ which I don't even mind ~ yet.

Also seen, but not not photographed: a bumblebee, a honey bee, ichneumonid wasp.

Not too shabby, for 7:30pm in the evening.