A Visit From the Psyllid Fairy

What happens when you lose a tooth?  You get a visit from the tooth fairy.  What happens when you write a blog post about hackberry leaf gall psyllids?  You get a visit from the psyllid fairy!!!

Envelope of psyllids and leaf galls - what a great surprise!

A parent of a lower school student, and an accomplished naturalist, learned about hackberry leaf gall psyllids after bajillions of them emerged from the leaf galls of the hackberries around her house.  She had saved some psyllids to identify them and brought some to my mailbox in an envelope after she saw last week's post.  Here's what was in the envelope:

Two hackberry leaves with galls and five hackberry leaf gall psyllids.

Those tiny dots in the picture above are hackberry leaf gall psyllids.  The large brown things are hackberry leaves.  I decided to have a microscope photoshoot with the psyllids, so I used a camera with a narrow lens and held it up to the eyepiece of a microscope to take the following picture:

Adult hackberry leaf gall psyllid at 20x magnification.

The psyllid in the picture above is long dead and a bit dried out, but it still looks pretty good for a dead bug.  Psyllids are true bugs, and true bugs are insects in the group called Hemiptera.  Hemipterans have mouthparts that are good for sucking plant sap, which is what psyllids are up to when they are living inside leaf galls.  You can see the mouthpart of the psyilld pointing down from the head, which is on the left side of the insect.  You can also see one of its antennae pointing to the left of the head. 

Two dried hackberry leaves, each with a leaf gall.

This time of year, the above leaves are all the evidence you'll see of hackberry psyllids.  The adult bugs have hidden away in bark or in cracks around the outside of your house.

Many thanks to the psyllid fairy for the fabulous psyllids!

Help! I've Got Hackberry Leaf Galls!

Last week students in our outdoor classroom sent the picture below, wondering what it was.  It's a very logical question, since those...things are growing out of what is obviously a leaf, but no normal leaf has weird miniature mushroom-shapes growing out of it.

Hackberry Leaf Galls (photo: M. Sherman)

The leaf above comes from a hackberry tree, whose bark I think is fantastic, and which we will explore later in the winter.  We have a gigantic hackberry tree in the outdoor classroom, and it's at the end of the row of parking spaces near the road.  Here's our hackberry:

Hackberry tree with most leaves already gone for the winter.

If you search through the fallen leaves around the classroom, you can find lots of hackberry leaves right now.  They have toothed edges (lots of tiny points), and they narrow to a tip.  Also, the wider end of the leaf usually is lopsided with one side larger than the other.  Most of the hackberry leaves have one or more of those big lumps on the lower side of the leaf.  The lumps are called leaf galls, and they are scar tissue the tree has grown in self defense against a parasite.

Three hackberry leaves, two with galls, one without.

So, what exactly is a parasite, you ask?  A parasite is a small organism that lives on a larger organism and often uses the larger organism for food, harming the larger organism in the process.  The larger organism is called the host.  There are lots interesting types of parasites in this world.  Dogs and cats sometimes have fleas for parasites.  Deer often have ticks.  Humans can sometimes have lice.  And plants can have parasites too.  The parasite on our hackberry leaves can only live on hackberries, not humans.  It is a type of insect called a psyllid (SIL'-id).  Psyllids look just like tiny cicadas - smaller than a grain of rice.

I broke open this gall, but it was empty.  The adult has already emerged from it.

Hackberry leaf psyllids lay their eggs on the underside of hackberry leaves in the spring.  The eggs grow into immature psyllids that look like this.  The psyllids damage the leaves, which causes the leaves to grow a lump of scar tissue (a gall).  The psyllids eat hackberry sap and live inside the gall as they grow larger through the summer.  In the fall, the psyllids grow into adults and drill out of the gall.  They fly or crawl to find crevices in bark or buildings to overwinter safely.  When the weather warms up in the spring, they lay eggs and start the cycle again. 

Hackberries grow well in Middle Tennessee, yet they almost always have hackberry leaf galls damaging their leaves.  The trees don't seem overly harmed by the gall psyllids' damage.  This is normal parasite behavior.  Most parasites don't cause extensive harm to their hosts.  They take just a little food from them but not enough to kill them.  If a parasite ate too much of its host and killed it, the parasite would be out of food and would die too.  Parasites use their hosts in a sustainable manner so that their food source will be available in the future.

Squishing the Squash Bugs

See those dots?  They're the little bronze balls at the center of the squash leaf in the picture below.  These are newly-deposited eggs of the gross squash bug. 

Squash bug eggs

 Squash bugs are attacking the zephyr squashes on the farm.  Zephyr squashes are green and yellow zucchini-like squashes.  They are very generous plants, and we have to collect them every two days while they are in season, or we'd be buried in giant squashes.

Yellow squash, zephyr variety

 Squash bugs belong to the insect order Hemiptera.  Stink bugs, aphids, cicadas and assassin bugs are also Hemipterans.  Hemipterans have piercing, sucking mouth parts (think sharp straws), only one pair of wings, and commonly have a shield-shaped patch on their backs.  They usually eat like kids consume drink boxes:  poke in the proboscis and suck out the liquid.  Most Hemipterans eat plant sap, but a few (like assassin bugs and toe-biters) specialize on blood or insect juices.  Technically, Hemipterans are the only bugs that can be called bugs.  They are the "true bugs" of the insect world.  All other bugs are just insects.

Squash bugs drink squash juice, which can be found inside squash plant leaves, stems and fruits.  They are voracious, and they can suck out so much squash sap that the leaves can wilt and smaller plants can just wither and die.  More commonly, they damage plants by walking through diseased portions of the plants and treading spores to other parts of the plant.  They also make little specks on zucchinis, acorn squash and other squashes, which reduces their retail value if not their food value.  In addition, they creep out their squash farmers.

Yes, there is a squash bug in the center of the picture

 Adult squash bugs are shy.  If you try to take a picture of one, they will constantly walk to the opposite side of the stem from where you are.  That is why the picture above is so lame.  They also congregate under dead leaves or other things on the ground.  One way to catch a lot of squash bugs is to set a board on the ground under an infested plant.  Then go back the next day and squish them all.  Or brush them into soapy water if you don't like squishing bugs.

Younger squash bugs are easier to find.  After they hatch, they hang out under squash leaves and gradually spread out over a few days.  I was 'lucky' enough to find this cluster of squash bug nymphs and get a picture before they scattered.  They are slower than adults, so they scatter slowly.  If you find a bunch of squash bug nymphs, you can brush them onto the ground and stomp them, or brush them into soapy water.

A billion little squash bug nymphs.

On the farm, we kill squash bugs if it doesn't slow us down from the rest of our work.  We also squish the eggs when we can.  Mostly we use timing to reduce the impact of the squash bugs.  Squash grow quickly, but squash bugs take almost a month to hatch and grow to fighting size.  By that time, the squash bugs are really cooking, the squash plants have been fruiting for a week or two.  Also, squashes grow so quickly, most of the squashes escape damage and can still be harvested.