Plant Galls Caused by Insects and Mites

Galls formed on a red maple leaf by the maple eyespot gall midge

“In all things of nature there is something of the marvelous.” Aristotle

Galls that occur on plants may be caused by insects or mites, nematodes, bacteria, fungi, or viruses. I think the more interesting ones are those formed by insects and mites. Plants that have rapid growth in spring are especially vulnerable to gall-forming insects, but often galls go unnoticed until later in the season. The chewing of the insects produces salivary secretions that cause an increase in growth hormone production in the plant tissue. This causes an increase in either cell size or cell number and results in abnormal plant tissue growth called a gall.

Galls likely from Eriophyid mites on poison ivy

Inside developing galls, the immature mite or insect feeds where it has protection from most predators. In the case of stem galls produced on goldenrods, the fly larvae inside may be eaten by woodpeckers who are savvy to the protein morsel that lies within. Leaf galls are normally not a health issue for the plant as enough unaffected tissue can still effectively photosynthesize.

Willow pinecone galls are produced a midge, Rabdophaga strobiloides 

 Black cherry spindle galls are the most common of the galls caused by Eriophyid spp. of mite. As the name suggests, they are found only on native black cherry, Prunus serotina, and especially on young saplings. Small finger-like galls are formed on new leaves in early spring on the upper sides of leaves. They are green at first, and then turn a bright red, and often occur in large numbers that are tightly packed. Leaves produced later in the spring and throughout the rest of the growing season will not be affected, as there is only one generation of this mite per year.

Spindle or finger galls on black cherry

Another unusual gall caused by an Eriophyid spp. of mite is the birch Erineum or velvet gall. This gall looks like pink fairy dust was sprinkled on the tops of the leaves and which then got very hard.  These galls can also be found on maple, linden and certain viburnums.

Velvet birch gall

Grape tube gallmaker galls occur on wild and cultivated grapes. The Cedidomynia viticola midge lays eggs on the grape leaf, and the leaf then responds by producing pointed tube galls. This gall maker is not of economic importance.

Grape tubemaker galls on wild grape

Cockscomb galls on elm are caused by an aphid, Colopha ulmicola. Aphid nymphsemerge in spring from eggs laid on elm twigs and begin feeding on newly emerged leaves, producing a gall that grows around the nymph. Green at first, the gall turns red later in the summer. Winged adults emerge from the leaf galls and fly to nearby grasses where they produce offspring that feed on grass roots. As these nymphs become winged adults in the fall, they fly to elms and lay eggs, and the cycle begins anew.

This elm cockscomb gall will turn red by summer’s end

Aspen petiole galls are formed by the Contarinia petioli midge and are found on cottonwoods and aspens. Each gall contains a single larva, which exits the gall in the autumn to pupate on the ground. This gall is formed at the leaf petiole and does not affect the leaf functions.

This red aspen petiole gall is hard to miss

Oaks seem to have the greatest variety of galls, especially those caused by gall-forming wasps. There are wooly galls, nipple galls, jumping galls and oak apple galls to name a few. The banded bullet gall wasp Dryocosmus imbricariae produces rather attractive twig galls.

Banded bullet wasp galls

The wool sower gall is caused by the tiny Callirhytis seminator wasp, and appears only on oaks, especially white oaks. The wooly galls resemble a toasted marshmallow as it turns from white to brown over time. Inside the gall are small, hairy seed-like structures, each containing a single, developing wasp larva. These structures get darker during the year and by late summer the entire gall is brown.

The wool sower galls later in the summer

Acorn pip galls, caused by the diminutive wasp Callirhytis quercusoperator, are located between the cap and the acorn. When the white gall pushes out, after the acorn has fallen prematurely, there is a tiny triangular hole left. These galls are generally found on red oaks. Ants sometimes chew the pip galls out of the acorn.

Two acorn pip galls pushing out

Colorful maple eyespot galls are caused by a midge, hickories are hosts for a large variety of gall forming insects, and willows have an interesting cone gall that occurs on new branch tips. There are also galls that form on herbaceous plants- the most identifiable ones being those on goldenrod stems caused by a stem gall fly. Downy woodpeckers go after the larva inside the gall.

Left- goldenrod rosette gall right- goldenrod stem gall

The next time you come across some interesting galls, see if you can break one open and find out if an insect is inside. The mystery will be solved, if so. It could be a nymph, a pupa or, rarely, an adult getting ready to chew its way out. Oak apple galls are the most interesting, especially if you find a female wasp that has just emerged from its pupal case.

Oak apple gall

Female oak apple gall wasp emerged minutes before from the apple gall

Galls on hickory leaf caused by a Caryomyia species midge

Pamm Cooper

 

Sights and Songs of June

Native mountain laurel blooms in June

Spring being a tough act to follow, God created June.

–  Al Bernstein 

June is the month where green has become the main the landscape color with flowers and some early fruits sprinkling a bit of color in gardens and wild landscape. It is a cheery time for me as the best is yet to come. Butterflies, bees, dragonflies and other insects are everywhere now and provide a little bit of interest as they go about their daily lives. I stop by the woods early in the morning to listen to wood thrushes, veerys, vireos, grosbeaks, catbirds, tanagers and so many other birds of the forest that sing so sweetly at this time of year.

Veery

Male common yellowthroat carrying an insect to its young

Wandering in my yard this week I found a little surprise- an enchanting Clytus arietis wasp beetle resting its little self on a fern. This diminutive, long-horned beetle has striking yellow markings on a dark brown to black narrow body and it has cricket-like back legs. Its larvae live in warm, dry, dead wood, favoring birches and willows. Adults can be found during the day from May- August resting in the open on low vegetation.

Colorful Clytus arietis wasp beetle

Maple eyespot galls are brightly colored circles of red and yellow that appear on the surface of red maple leaves in early June. Caused by the ocellate gall midge Acericecis ocellaris, this tiny fly deposits eggs on the underside of red maple leaves, which causes a chemical response in the leaf at each spot an egg was laid. The larva hatches and feeds on leaf tissue within the small disk- shaped gall that was formed.

Maple eyespot gall

Ebony jewelwing damselflies Calopteryx maculate are easily identified by their  metallic iridescent green/blue color and totally black wings. They can be found near streams and rivers, but are especially common found near shallow streams in forests. This damselfly is unlike other jewelwings because it is the only one that sometimes rambles far from water.

Ebony jewelwing damselfly

White-tailed deer fawns are generally born from late May to June and can sometimes be seen trying to keep up with their mothers early in the morning. They often get exhausted doing so and collapse to rest, sometimes in unusual places. Fawns are generally left alone during the day and the doe will return at dawn and dusk to feed her fawn and sometimes move it along to a safer place.

fawn tired from following its mom

Blue-eyed grass and orange hawkweed are blooming in the wild now, as are wild geraniums, beautybush, viburnums, bearded irises, Carolina spicebush, mountain laurels, tulip trees and raspberry. Grape should be flowering soon as will catalpa trees. Catalpa flowers are pollinated by several species of sphinx moths, who visit flowers mostly during the night.

Blue-eyed grass Sisyrinchium albidum is not a grass but a member of the iris family

Orange hawkweed

Butterflies and moths are more abundant now as we have warmer weather and plants that have leafed out. Giant silkworm moths like the beautiful luna moth emerge from mid-May through summer. Many are strongly attracted to lights and are often found resting on the sides of buildings where lights are left on all night. These large moths do not feed, but live off of stored food until they mate, perishing soon after. Red spotted purples and tiger swallowtails are just a couple of butterflies that visit my property and lay eggs on some black cherries planted a few years ago.

The fabulous Luna moth, one of our native giant silkworm moths

Red-spotted purple butterfly seen June 5 2020- the first of the year for me

Walking through a woodland path at a nature preserve I heard a buzzy high-pitched call above me and saw a blue-gray gnatcatcher sitting on her eggs in a nest. The nest was well camouflaged with a coating of lichens so it blended in perfectly with the lichen encrusted branches all around it.

A blue-gray gnatcatcher nest is barely visible in the crotch of this tree

There is so much going on in the outdoors now wherever you happen to go. There are so many flowers yet to bloom, and so many young animals and birds just getting to know the world around them. As I watch bees and butterflies, and listen to the birds sing and the tree frogs trilling away day and night, I think Aldo Leopold got it just right when he wrote “ In June, as many as a dozen species may burst their buds on a single day.”

A little surprise

Pamm Cooper

 

 

 

 

 

 

Things I See Outside This Week

The gorgeous flowers of the  horse chestnut are blooming this week. Aesculus hippocastanum is commonly called European Horsechestnut or Common Horsechestnut. The massive trees are fast growers and need plenty of room to spread out and reach high. Never plant one near or under power lines. The panicle flowers are normally white with parts of pink and yellow. There is another variety with pink flowers as shown below. Horsechestnut fruit is not edible for humans and are called conkers. The shiny nuts look nice displayed in a dish for nature lovers, just don’t try to crack and eat them!

Red Horsechestnut Flower

Luna moth sighting have been reported around the state this week. They are a strikingly large and beautiful, with only a brief seven days of life in its adult stage. They are nocturnal spending the night seeking a mate with females laying eggs for next year’s generation. Occasionally they will fly towards a light even landing on a screen door with lights on inside. Host trees providing leaves for caterpillars to eat are walnut, hickory, sweet gum, and paper birch.

Luna Moth

In the vegetable garden asparagus beetles are very active, feeding, mating and laying eggs. As can be seen in the lower photo, eggs are laid on on point sticking horizontally at a 90 degree angle to the stem and off of the flower bud stem. Crush all eggs by running you hand up and down each stalk. Catch adults beetles and crush or drop into a container of soapy water to rid them from the asparagus patch.

Asparagus Beetle

Asparagus Beetle Eggs

Another oddity was sent to my office this week. This is an Apple Oak Gall produce by a developing tiny, cynipid wasp. The adult female wasp injects the egg and a chemical into leaf tissue, causing the leaf to distort and makes a home and food for the newly hatched larva. Once the larva is big enough, it pupates inside the gall, only coming out once the gall is empty and dry. There are not enough wasp and galls to cause harm to the tree, so they are only considered cosmetic not a pest.

Apple Oak Gall

Another gall I found this week was the Wool Sower Gall on a white oak tree.  The gall is caused by secretions from the developing wasp larva, secretions of , (Callirhytis seminator). These galls and wasp damage are also not harmful to the tree. The wasps are not dangerous to humans as they do not sting.

Wool Sower Gall on white oak.

Other galls we have seen in past made by insects are the grape tube gallmaker galls on grape leaves, (Schizomyia viticola). Grape tube gallmaker is a species of mite that forms a gall on New World grape leaves. Larvae feed inside the tubes and are free from predators as they feed on the deformed plant tissue. Again only cosmetic to the plant.

Grape Tube Galls on grape leaf.

Finger galls form on a cherry leaf below. Eriophyid mites are the gall makers here. They are microscopic mites developing inside the raised, malformed tissue. Mites can be identified by the structures they create on their host plant.

Finger Galls on a cherry leaf.

Velvetleaf galls on sweet birch develop from the feeding of the  velvet eriophyid gall mite.  Reddish-patches are called an erinea, can also occur on silver maple. (JLaughman photo).

The soil bacterium, Agrobacterium tumefaciens, can cause galls, tumors in this case, on the crown, roots and sometimes branches of susceptible host plants. Euonymus is commonly infected. The bacterium can enter a plant via any tissue damage that normally happens during pruning or transplanting. Agrobacterium tumefaciens is also used as a tool in the laboratory in genetic engineering to introduce genes into plants in a natural way.

Crown Gall, Agrobacterium tumefaciens.

-Carol Quish

 

August in the Outdoor Landscape

Tiger swallowtail on obedient plant flower

“What dreadful hot weather we have! It keeps me in a continual state of inelegance.” – Jane Austen

What a strange summer we have had so far in New England! I almost thought of going to Florida to escape the heat and humidity. It has been hot and humid, no doubt, but it is August after all, and things are coming along nicely in the out- of-doors. This time of year there is enough good stuff going on in the landscape to overcome any weather difficulties we may be experiencing, so let’s plod on out and see what’s happening.

foggy morning on Horsebarn Hill UConn

 

 

As we head on into the mid= summer, most garden buffs are by now reveling in the abundance of hydrangeas that are now in bloom. The dwarf ‘Little Lime’ is one of several panicle Hydrangeas that have nice full-bodied lime green flowers that pack a visual punch in the landscape. ‘Little Lamb’ is another of the smaller panicle hydrangeas, this one also having a compact form with pure white, ethereal blooms that give it its name.

‘Little lamb’ panicle hydrangea

Hibiscus are also blooming now, with their outstanding large, colorful flowers that really provide some visual excitement in the garden. I came across a nice hedgerow type planting that made a nice privacy screen along a sidewalk. I am not really a hibiscus fan, but a pink- flowered one popped up in my garden, and looks so great there that I guess it can stay. I wonder if someone snuck it in there to get me to have kinder thoughts toward these plants…

Hibiscus

On the wild side, the sweet- smelling Clethra alnifolia is in full bloom and is attracting all types of bees, beetles and butterflies. Look for this small clump-forming shrub in any areas where soils are moist. The white flower spikes are very fragrant, so you can tell where Clethra are long before you actually see them. Groundnut vine is also blooming now, with its pea-like pink flower clusters dangling from its twining stems. Often found twining itself around goldenrods and blue vervain, it is always fun to come across this plant.

Red spotted purple butterfly on Clethra

The barn swallows that are partial to building their nests on the eaves of our equipment building have had their second brood of the year, as have bluebirds. Hopefully that will exit the nest soon and mom and dad can have a much needed rest in the near future. There was a female wood duck taking her brood on a tour in a large beaver pond the other day.

barn swallows ready to fledge

Juvenile wood ducks

I came across a wild grape that had one leaf covered with interesting cone- like galls formed by the grape tube gallmaker midge (Schizomyia viticola). This is a harmless gall, and only affected one leaf on the entire grape plant. Looks like a bunch of tall red, skinny gnome caps were set on the leaf.

grape tube galls

Combing through garden centers for great plants is always enjoyable when you find something like the Blackberry or leopard Lily Belamcanda chinensis. Star shaped flowers only 2 inches wide are heavily spotted with red, while foliage is sword- shaped. The flowers appear in late summer and bloom until frost, so this is a good plant to spiff up areas where other perennials are fading into the sunset.

leopard lily Belamcando chinensis

Interesting plants suitable for containers are agave and other succulents. I saw a good size Agave colorata recently which was very striking in appearance. Its leaves are thick and powdery blue- gray with unusual cross- banding designs on them, plus leaf edges have brown teeth tipped with spines. A spectacular plant!

Agave colorata

patterns on Agave colorata leaves

Caterpillars this time of year are larger and, in my opinion, more interesting than the early season caterpillars. One favorite is the brown- hooded owlet, which is a sports a rich array orange, blue, yellow and red. Look for this caterpillar on goldenrods, where it feeds on flowers and flower buds.

brown-hooded owlet

If you want a nice surprise, with a little careful handling you can check inside folded stinging nettle leaf shelters and may find either caterpillars of the comma or red admiral butterflies, or the chrysalis of the red admiral.

red admiral butterfly chrysalis inside a leaf shelter on stinging nettle

 

The skies can provide some viewing that is better than any television show. Thunderhead clouds can provide some drama as they develop on hot and humid afternoons, and may provide further excitement in the form of thunder and lightning, and rainbows may follow. We can have remarkable sunsets any time of year, so don’t forget to have a look at the sky around sunset. August is also a great time for early morning fogs as well, especially when we have had a humid night. Getting up early does have its good points…

Thunderhead developing on a hot and humid afternoon

 

Pamm Cooper

 

Outdoors in Late Spring

A striped Jack-in-the- pulpit just off a bike trail

“Nature gives to every time and season some beauties of its own.”

-Charles Dickens

As we move into late spring, especially after the rather gray, wet spring we have had so far, the sunny, warmer days of late bring a little excitement to both gardeners and hikers alike. Plants are starting to provide lush green backdrops for their flowers, while insects, animals and birds are increasing their activities. Gardens centers are providing bountiful selections for everyone, and there are new cultivars every year to provide interest in the landscape. As we move into a more outdoorsy mode of life, we can have encounter pleasant surprises wherever we may go in our travels.

For instance, at this time of year, female turtles of many species are commonly seen as they leave their normal adult habitat and go off searching for egg- laying sites. For the past two years, I have found two different spotted turtles in almost the exact same place, at almost the same date as they travel back from laying eggs. These are different turtles, though, as the spotting patterns are remarkably different.

Spotted turtle on the move- May 30 2018

A surprise discovery for me this year was when I noticed a number of tiny, barrel- shaped leaf rolls on a small oak sapling. Some insect had cut the lobes and then rolled them up tightly while still attached by the midrib. After some research, these structures were found to be called a nidus (Latin for nest) formed by the female leaf- rolling, or thief weevil Homoeolobus ssp. An egg is laid within the leaf before the third roll is made.

Work of the leaf-rolling weevil

Plenty of plant galls can be seen now, especially on oaks. One interesting gall is called the wool sower gall, which is formed on oaks by the larval feeding of the certain wasps. The gall resembles a toasted marshmallow, with white fibrous masses that at first have a yellow- seed like capsules though out the gall.  Each capsule contains a wasp larva.

Gall formed on an oak by the wool sower gall wasp

In the town where I live, there is an unusual tree growing in a woodland wetland area. I noticed it several years ago only because of the striking white flowers that stood out amidst all the green foliage of native trees and shrubs. It was identified by a tree expert as a Fraser magnolia which is native to the southern Appalachians. He thought it was probably brought here in the late 1800’s or early 1900’s by people who had a homestead on this site, who perhaps came from that area of the country.

Fraser Magnolia in the wild in Manchester, Ct.

Insects are more noticeable now as more species increase in both numbers and activity, including, unfortunately, the notorious lily leaf beetle. Check Asiatic day lilies for eggs and larvae now. And the giant silkworm moths are emerging from their cocoons now. I had the impressive eyed click beetle land near me the other day, and shortly after that encountered the first gray hairstreak butterfly of the year. Always a positive experience for me to see any butterfly- except maybe the cabbage white…?

eyed click beetle

Gray hairstreak spotted in late May

Deer are looking a bit scraggly as they lose their winter coats, and early June is the time that fawns are born. Raccoons also have their young this time of year, as well. Fox kits should already be accompanying  their parents of hunting forays.

Baby raccoons- maybe two weeks old

Lady slippers, wild geraniums, columbine, black cherry and other native plants are blooming now. And if that isn’t enough, you can always get some interesting flowers to enjoy at home. An unusual offering from the Tri-county Greenhouse in Mansfield Depot is the bat-faced heather. And a Thunbergia alata cultivar called “Tangerine slice’ is striking if you are looking for a good vining plant.

Wild columbine and Geranium maculatum by a roadside

Bat-faced heather

Tangerine slice Thunbergia– Pamm Cooper photo

You never know what things of interest you may see, whether in the great outdoors or a good garden center. Image the unexpected pleasure of seeing a couple of ducks who were enjoying being taken for a walk on an airline trail. That was the best surprise for me on that particular day in the great outdoors!

Crowley and Dean out for a walk

 

Pamm Cooper

 

 

 

 

 

 

 

 

 

 

 

 

Galls & Burls Explained…Sort of

Trees and other woody plants often have large or interesting swellings on their trunks or branches.   The cause is often difficult or impossible to determine.  Possible causes include fungi, bacteria, insects, mechanical or environmental injury, or genetic mutation.  The terms gall, tumor and burl are commonly applied to describe these abnormal swellings. 

Galls and tumors can be any size or shape and may occur on both woody and herbaceous plants and plant parts.  The swelling occurs as cells divide more rapidly than normal (hyperplasia) and/or due to excessive cell enlargement (hypertrophy).  Burls are generally considered to be large woody swellings that are basically hemispherical in shape.  They often bear many buds and sometimes sprouts.   The burls of black walnut, coast redwood, sugar maple and black cherry are highly prized by woodworkers for their beautiful swirling or ‘bird’s eye’ grain.   This relatively small burl from an apple tree (cause unknown) has an interesting surface pattern and interior grain showing bud traces.

Burl from an apple tree trunk.

 

Tiny brown lines are bud traces.

An individual tree may have one or many swellings.  On this maple tree, the many swellings are of unknown origin.  Often, a tree with large or numerous galls will decline earlier than a tree without them. 

The most common bacterial gall disease is crown gall caused by the bacterium Agrobacterium tumefaciens.   This soil-borne bacterium enters the roots of the host plant through wounds caused by planting, cultivation, frost heaving, insects or nematodes.  The bacteria, upon attaching to the plant cell walls, send DNA that causes production of plant growth hormones into the plant cell where it is incorporated into the plant cell chromosome.  Affected cells begin to multiply at an uncontrolled rate, resulting in visible tumors within 2-4 weeks.   More than 600 plants are susceptible to crown gall.  One of the most common, where galls occur on both roots and stems, is Euonymus, shown in the photo. 

Crown gall of Euonymus.

 

Examples of galls caused by fungi include azalea gall (Exobasidium vaccinii), black knot of plum and cherry (Apiosporina morbosa), and Fusiform rust of pine (Cronartium quercuum).    More information on these diseases is available by clicking on the name of the disease. 

 A close up of a leaf gall on azalea . (Plant Disease Diagnostic Clinic, Cornell University)

Black knot of plum and cherry.

 

 Fusiform rust (USDA Forest Service – Region 8 – Southern Archive, USDA Forest Service, Bugwood.org)

Insects and mites cause some very interesting galls on leaves as shown in the photo.  These usually cause little damage to the host plant or tree and control measures are not normally recommended.  A new theory is being explored by scientists that the swellings associated with these arthropods may in fact be caused by bacteria transferred to the plant tissue during feeding.   Fascinating! 

Hickory gall phylloxera.

 

Galls can be caused by cultural, mechanical and environmental factors including graft incompatibility, wounding, and freeze injury.   Galls on some conifers that vary from small to huge (several times wider than the trunk) are thought to originate when the trees are young seedlings from a single cell and enlarge for many years.  Low temperature injury is suspected, but not proven, as the cause. 

J Allen