Biological Control of Purple Loosestrife

It's the height of summer, and the Purple Loosestrife in my detention pond is in full bloom.

However, when I say full bloom, I mean FULL bloom.  For here in North America, Purple Loosestrife, aka Lythrum salicaria, is a highly invasive plant.

Just some of the Purple Loosestrife in my detention pond

There's no denying that this particular invasive is a strikingly gorgeous plant.  Hailing from Europe and Asia, this wetland plant has been prized throughout history as an ornamental in the garden in addition to its medicinal use for gastrointestinal ailments.

Overseas, there are a number of cultivars of Purple Loosestrife.  'Blush', which has pale pink flowers and 'Feuerkerzeze', which has sterile, vividly-colored double flowers, have both won the British Royal Horticultural Society's Award of Garden Merit.

Hummingbird Clearwing Moth on Purple Loosestrife

In the 1800's Purple Loosestrife was introduced into North America either accidentally as seeds floating in ship ballast water or intentionally as an ornamental.  In the years that followed bee keepers spread it to other parts of North America, as its many flowers offered an abundance of nectar for the bees.  It has since spread into most US states and up into Canada.

While bees and other pollinators love the flowers, unfortunately there are not many animals or insects here that eat the plant to keep it in check.  Purple Loosestrife invades wetlands, crowding out native plants.  It forms dense, impenetrable stands that are unsuitable for native wildlife such as ducks, frogs and turtles, and these animals are often forced to relocate. 

Once Purple Loosestrife is established in an area, it is nearly impossible to get rid of due to the immense number of seeds each plant produces.  A mature plant can produce millions of seeds, and these seeds remain viable in the soil for years.  It can also re-sprout from any pieces of roots left in the soil or water.  Managing this invasive plant by manual removal, burning, cutting, herbicides, and water management have all been tried... and found to be either too difficult, too costly, or environmentally unsuitable. 

So what to do about this plant?  In the mid 1980's, biologists began to search for what is usually the last resort - a biological control.  Biological controls are very tricky, as we have found out over the years.  Deliberately introducing something new into the environment can go terribly wrong.  Asian ladybugs that were released to fight aphids have now edged out many of our native ladybugs.  Our largest native moth, the Cecropia silk moth, is now under attack from a parasitic fly that was meant to control gypsy moths.  And most of us know what happened with Kudzu, aka 'the vine that ate the South'...

Thankfully, testing for a biological agent is now much more rigorous.  Scientists considered over 100 insects overseas that were known to feed on Purple Loosestrife.  Several were thought to have possibility, and extensive testing began in Europe.  The insects were exposed to many North American species of plants to make sure that they would not end also attacking our native plants if introduced here.  In 1992, after six years of testing, the US Department of Agriculture approved four insects for release into the US for the control of Loosestrife:  two leaf-eating beetles (Galerucella calmariensis and Galerucella pusilla), one flower-feeding weevil (Nanophyes marmoratus), and one root-boring weevil (Hylobius transversovittatus).

Hylobius transversovittatus on Purple Loosestrife
(photo via wikipedia)

Would these biological controls work?  In the mid 1990's the U.S. Fish and Wildlife Service began releasing the leaf-eating beetles in various suitable areas, including two National Wildlife Refuges here in Massachusetts.  Between 2000 and 2008 the state government teamed up with various wetland conservations programs to release more beetles in Massachusetts through the Purple Loosestrife Biocontrol Project.  Beetles were released at 43 sites throughout the state, starting with Turner's Pond in Walpole, just a few towns away from me.  Within four years, Turner's Pond saw an 80% drop in Loosestrife plants.  This biological control worked!

However, to be a true success, the release of the beetles should not cause any negative effects on the environment.  Studies have found that the beetles do sometimes feed on two similar native plants; however they prefer Purple Loosestrife, and no serious problems have been reported.  Monitoring will continue, but so far this is one biological control that is a success!

Now I just need some of those beetles to fly over to my detention pond...

With all this Purple Loosestrife, I have quite a good meal for them!

Earthworms Gone Bad

Most of us grow up hearing about how great earthworms are for the garden.  Gardeners strive for a garden full of beneficial worms!  They aerate the soil, break down organic matter from the soil surface, and expel their nutrient-full 'castings' (aka 'poop') underground for the benefit of plant roots.  Whenever I found earthworms on our driveway after a rain, I enthusiastically picked them up and placed them in whichever part of the garden I thought needed them the most.

Then came the discovery of the invasive Asian jumping worm.

Asian jumping worm

Believe it or not, here in New England we don’t have any native earthworms, as glaciers wiped them all out several millennia ago.  With no earthworms, our hardwood forests evolved in an environment where fallen leaves collect in a thick layer on the forest floor and decompose slowly.  This leaf litter retains moisture, maintains the soil’s pH level, and supports a rich understory as well as the wildlife that live in such an environment.  

Yellow trout lilies

However, in the 1600’s, European settlers introduced earthworms back to the Northeast.  These non-native earthworms alter woodlands by eating the leaf litter that normally supports native tree seedlings and native wildflowers such as trout lilies, mayflowers, and trillium.  

Trillium cuneatum

The disappearance of this spongy leaf layer leads to the disappearance of insects and amphibians that live in it, which has larger implications in the forest ecosystem.  Thankfully this process is very slow, as the worms do not spread very quickly by themselves.

Enter the Asian jumping worm.

Asian jumping worms have likely been in the South and in northern greenhouses for several decades. However, they were noticed in 2013 in Wisconsin as problematic, and since then awareness has grown about these earthworms, which are.... a little different.

Asian jumping worms are more energetic than other worms.  Hailing from Korea and Japan, they are also known as ‘crazy snake worms’, as they thrash wildly side to side and even jump when handled.These worms have a voracious appetite, able to break down wood mulch and plant debris extraordinarily quickly.  (In one study, researchers from University of Wisconsin - Madison studied plots of forest land newly invaded by worms and found that the worms decreased the leaf litter mass by 84 to 95% in just four months!)

Instead of dwelling in deeper soil, Asian jumping worms live close to the soil surface, right underneath the leaf litter. Their dry, but nutrient-full castings are mostly left in the top two inches of soil, inaccessible to deeper plant roots. They work so quickly that scientists liken it to a dose of quick-release fertilizer.  However these nutrients easily wash away - sometimes to where people do not want it, such as in waterways.  Soil occupied by jumping worms often looks churned, grainy, and dry, and it is more prone to erosion.  

These worms that I had so carefully rescued were Asian jumping worms, of course, and they are changing the soil in my garden. The top layer of my soil in many parts of the garden has turned into a gravelly field of loose, dry little pellets.

While Asian jumping worms do thankfully die off in cold weather, their cocoons survive to hatch the next spring.  Another difference between these worms and others: it takes just one.  Jumping worms can reproduce asexually, thus it takes just one worm to make a colony in a new location.

So how can you tell if you have these crazy worms?

Asian jumping worm

It's difficult to tell with young worms, but the adult jumping worms can be identified by their smooth, light-colored clitellum, which completely circles its body near the head.  (The similar-looking European nightcrawler has a raised clitellum instead of a smooth one.)  They also wriggle wildly (or jump!) when picked up or touched.

So what can be done about these invasive worms?  Several states have launched campaigns to discourage people from dumping worms from fishing bait and vermicomposting in the woods, which exacerbates the problem.  Several organizations in Wisconsins have even cancelled their annual plant sales in order to slow the spread of these worms.  As for us, we can make sure not spread these worms by checking plants that we buy or share with others for worms and destroying any that are found.  Acquire compost only from reputable sources where it has reached properly high temperatures, which would kill any cocoons.

As for me, I will stop rescuing these invasive worms and putting them in my garden.

Excited For Aphids

Every year without fail, some of the leaves on my River Birch change, becoming weirdly distorted and deformed.

This leaf distortion is actually caused by aphids - Spiny Witch Hazel Gall Aphids, to be exact - which feed on birch leaves starting in the spring and then eventually move on to Witch Hazel trees for the second part of its life cycle.  The infested birch leaves ultimately shrivel up and fall off the tree prematurely.

So it's a bad thing for your tree to be attacked by aphids every year, right?

Surprisingly, it can actually be a great thing!  The infestation of aphids is usually not heavy enough to harm the health of the tree.  It does, however, attract all sorts of beneficial predators to the garden.

The infected birch is like a magnet for ladybugs.  There are always a lot of them on my tree.  They eat the aphids and lay their eggs there.  The larvae that hatch eat even more aphids and eventually turn into even more ladybugs for the garden.

ladybug larvae eating aphids on birch leaf

Other interesting insects attracted by the aphids include this Tree Cricket nymph. Tree crickets and their nymphs love aphids and scale insects and can be beneficial to a garden (though they can occasionally become a pest for orchards as they also like fruit).

Tree Cricket nymph on birch leaf

Believe it or not, there are actually beneficial wasps to have in the garden, such as this little Mason Wasp.  They prey on many larval insects including aphids and are non-agressive and rarely sting.

 My favorite things that are attracted by the aphids, however, are the birds.

Baltimore Oriole

Most of the birds that I see eating aphids on the tree are ones that I see commonly at my nearby bird feeders.  The Baltimore Orioles, though, have never come to a feeder (despite my attempts).  I only see these beautiful birds up close when they come for the aphids.

It makes you almost want an aphid infestation, doesn't it?

The Last Daffodil and What Eats It

This week temperatures have skyrocketed, but until recently it's been quite a cool (and sometimes downright chilly!) spring.  The last daffodil in my collection to bloom this year, Narcissus 'Actaea', flowered for over three weeks from mid-May through the end of last week.

Narcissus 'Actaea' - last daffodil bloom this year

The winding down of daffodil season, however, is when the fight to save my daffodils steps up.   In May and early June is when the critters that eat them come out to play.  And just what eats daffodils, the bulb that is impervious to almost every other garden pest around, you might wonder?

the Narcissus Bulb Fly

Frank from the garden blog Sorta Like Suburbia first told me about this fly, whose larvae burrows into the bulb and eats the middle of it, weakening or killing the plant.  After a quick google search, I knew I had seen this fly in my garden.  (Thank you, Frank!)  It's a good-sized fly whose various colorations mimic bumblebees, and when it flies it makes a distinctive whining sound.

Narcissus Bulb Fly

The adult flies emerge in late spring/early summer and live for 2 to 3 weeks.  I often see them around my flowers on sunny days this time of year, feeding on nectar and pollen.

After mating, the female flies lay anywhere from 40 to 100 eggs each at the base of suitable plants, one to three eggs per plant.  That's a lot of infested plants!  They usually lay eggs on daffodils, but they will also infest snowdrops, hyacinth, iris, lilies, amaryllis, and tulips, among others.

Narcissus Bulb Fly laying egg at base of daffodil leaves

After a few days the eggs will hatch and a larvae will wriggle down the outside of each bulb to feed on the basal plate that is on the bottom of the bulb.  It then bores into the middle of the bulb to feed on it, hollowing out the middle of the bulb as it grows larger and larger.  The larvae overwinters inside the bulb, and in early spring it pupates for a month or two (either inside the bulb or in nearby topsoil), finally emerging as an adult fly.

Of course, this usually spells disaster for the plant.  Sometimes the larvae's damage won't totally kill the bulb, and it will be able to send out small leaves and slowly recover over the next two or three years.  Unfortunately oftentimes the bulb is destroyed beyond recovery.

Thus I have been busy fighting these pests for the last weeks.  The Narcissus Bulb Fly is a tough fly to control.  Some people have luck using systemic insecticides, however I try to garden as organically as possible.  Daffodil growers often use hot water bath treatments to kill larvae from Bulb Flies and other pests.  To do this, after the leaves have died back, dig up bulbs that might be infested and submerge them in hot water that is 109° to 111° F (42°-44° C) for one hour.  The heat will kill the larvae; just make sure to avoid higher temperatures that cook the bulb!

I go for a slightly less complicated route - I become a Fly Hunter for the few weeks that they are out in the garden.  I am out gardening quite a bit this time of year, so I garden with a butterfly net handy.  I listen out for the familiar whine when gardening and often check the flowers that they particularly frequent.   When I see a Narcissus Bulb Fly, I swoop the net on top of it.  The fly usually flies straight up to the top of the net, so I then carefully gather the material around the fly and bring it somewhere I can stomp on and kill it.  So far this year I've killed about two dozen flies.

Here's hoping that it's enough to save most of my daffodils.

SaveSave

The Quest for the Best Tasting Tomato

"You have to grow Black Krims," a relative advised me.  "They are the best tasting tomatoes by far!"  Others disagreed, claiming that the award-winning Brandywines deserved the honor of top tomato.

Black Krim heirloom tomatoes

Both Black Krim and the Brandywines (of which there are several strains) are notable heirloom tomatoes, and both have won many accolades, but which was the best?  This summer I was on a quest to grow these tomatoes that I had heard so much about - and determine once and for all which was truly the top tasting tomato.

So which one won?

Which tomato was the best tasting, 

the cream of the crop, 

the king of the garden, 

all that and a bag of chips?

I don't know.

The *$&^! chipmunks ate every single one of the Brandywines.

Yes, you.

I managed to save some Black Krims and other types of tomatoes that I had in the greenhouse by putting up a screen door to keep the chipmunks out, but every. single. tomato that grew outside in the vegetable garden was a goner, which included every Brandywine I had.

half-eaten tomato

Likely thanks to the drought, the chipmunks went wild in the garden this year, even gobbling up all of my kids' favorite ground cherries while they were still green. (Aren't ground cherries supposed to be somewhat toxic until totally ripe?)  I tried putting pepper spray on the tomatoes and ground cherries, but either I couldn't keep up or my chipmunks have developed a liking for spicy food.

a chipmunk in what he thinks is his own personal ground cherry patch

I did eat some of the treasured Black Krims, and yes, they were amazingly delicious.  But can I say they are the absolute best tomato of all?

It looks like I will be on the quest yet again next summer to determine the answer to that question.

And here I thought squirrels were the worst.

Anyone else have a favorite type of tomato?

And maybe a really great recipe for chipmunk repellant?

SaveSaveSaveSave
SaveSave
SaveSave
SaveSave
SaveSave
SaveSave

Straggling in to the End of Summer

Here in Massachusetts we've been having a drought, so we were all so thankful to finally get some rain yesterday.

Hibiscus 'Cranberry Crush'

It's been so hot this summer that I've had trouble going out to the garden to weed.  (How did I use to garden down south in North Carolina?)  My garden is looking rather neglected.

Every summer I wonder why it is that the weeds thrive on heat and drought, while the plants we want throw up their hands and cry uncle.  Thankfully many of my plants are pretty drought tolerant - or at least the ones that aren't drought tolerant have died already so I don't notice them anymore.  (Sometimes it pays to have a short memory.)

Thank goodness for Purple Coneflowers and Cosmos!

The veggie garden has been a struggle this year.  The plants are doing fine, but I am not reaping the fruits of my labors.

half-eaten green tomato

The chipmunks, on the other hand, obviously feel like they are at an all-you-can-eat garden buffet.  They've eaten almost every tomato and ground cherry the garden has produced.

I no longer think chipmunks are cute.

At least the chipmunks don't like onions!

The snakes that used to live out behind our neighbor's house must have moved away as we've seen so many critters move in this summer in addition to the normal band of roving deer.  One rascally groundhog, a small horde of chipmunks, and two bunnies have settled in this year.  (I'm expecting around 100 little bunnies next year.)

But I've spotted a few beauties around the garden, too.

Clearwing Moth and Lantana

I always welcome the pollinators to the garden.

bee on Liatris

It is interesting how different years see rises in different populations of butterflies.  While I haven't seen a lot of butterflies in general this year, there have been a number of Swallowtail butterflies, especially Spicebush Swallowtails, which I am delighted by.

In other news, this past weekend marked five years since I started the Red House Garden blog.  I can't believe it's been five years already.

Happy gardening, everyone!