Cedar Apple Rust Prevention and Treatment: A Simple Guide for Healthy Trees

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Cedar apple rust is a fungal disease caused by Gymnosporangium juniperi-virginianae, which affects apple trees and junipers, such as red cedars and ornamental junipers. This fungus requires two hosts to complete its lifecycle, infecting leaves and fruits of susceptible apple cultivars and potentially causing premature defoliation if the infection is severe [^1^].

Preventing and treating cedar apple rust is essential for maintaining healthy apple trees and junipers. Methods for controlling the disease involve both cultural practices and chemical treatments. For example, planting resistant apple cultivars or ensuring adequate distance between apple trees and junipers to disrupt the fungal lifecycle can help reduce the impact of cedar apple rust on your plants[^2^].

Additionally, chemical treatments such as fungicides can be effective in managing cedar apple rust. Timing and proper application are crucial for successful disease control, as treatments should be applied just before infection periods and repeated as necessary throughout the growing season. Consulting local extension services for specific recommendations tailored to your region can be helpful in developing a successful prevention and treatment plan[^3^].

Understanding Cedar Apple Rust

Life Cycle

Cedar apple rust is a fungal disease caused by Gymnosporangium juniperi-virginianae. It requires two host plants to complete its life cycle:

  • Rosaceae family (apple, hawthorn, serviceberry)
  • Cupressaceae family (eastern red cedar and other junipers)

The fungus produces spores on junipers, which are released and then infect plants in the Rosaceae family, and vice versa. The entire life cycle takes 1 to 2 years to complete.

Symptoms and Signs

On Apple Trees

  • Yellow spots: These appear on leaves and fruit, which later turn bright orange to red.
  • Aecia: Raised, tube-like structures develop on the underside of the diseased leaf or fruit.

On Juniper Trees

  • Telial horns: Greenish-brown, jelly-like structures that form on juniper twigs during wet weather.
  • Gall formation: Round galls, up to 2 inches in diameter, form on infected twigs.

Here’s a comparison of symptoms and signs on the two host plants:

Host Plant Yellow Spots Aecia Telial Horns Gall Formation
Apple Yes Yes No No
Juniper No No Yes Yes

Prevention and Treatment

  • For apple trees, select resistant cultivars.
  • Regularly inspect trees for signs of infection and remove infected material.
  • Remove alternate host plants within a large radius, if possible.
  • Apply appropriate fungicides to protect susceptible plants during the infection period.

Host Plants and Varieties

Apples and Crabapples

Cedar apple rust affects both apple and crabapple trees. These trees are part of the Rosaceae family. Susceptible varieties include:

  • Golden Delicious
  • Rome Beauty
  • Jonathan

Resistant varieties include:

  • Red Delicious
  • McIntosh
  • Enterprise

Junipers and Cedars

The primary alternate host for cedar apple rust fungus is the juniper species, particularly Juniperus virginiana (eastern red cedar). The fungus also infects ornamental junipers and cedars.

Susceptible juniper varieties:

  • Rocky Mountain juniper
  • Juniperus scopulorum

Resistant juniper varieties:

  • Juniperus chinensis ‘Pfitzeriana’
  • Juniperus horizontalis ‘Wiltonii’

Hawthorns and Other Susceptible Plants

Hawthorns are another host affected by cedar apple rust. Other susceptible plants include serviceberry and quince, also in the Rosaceae family. To reduce the disease’s impact, consider planting resistant varieties of these plants.

Pros of using resistant plants:

  • Less instances of infection
  • Reduced need for treatments

Cons of using resistant plants:

  • Limited variety choices
  • Potential for reduced fruit quality in some cases

A comparison between susceptible and resistant varieties:

Plant Susceptible Varieties Resistant Varieties
Apple and Crabapple Golden Delicious, Rome Beauty, Jonathan Red Delicious, McIntosh, Enterprise
Juniper and Cedar Rocky Mountain juniper, Juniperus scopulorum Juniperus chinensis ‘Pfitzeriana’, Juniperus horizontalis ‘Wiltonii’
Hawthorn and other plants Most common hawthorn species Cultivars showing some resistance

Prevention and Control Measures

Cultural Control

  • Remove nearby red cedars or ornamental junipers to break the disease cycle, as cedar-apple rust requires both host plants.
  • Prune and space trees for better air circulation, reducing moisture retention and fungal growth.
  • Dispose infected plant material, preventing fungal spores from spreading.

Fungicides and Spraying

  • Apply copper-based fungicides at the start of the growing season to protect apple trees.
  • Regularly spray fungicides during wet or humid conditions to prevent infections.
  • Monitor weather conditions and adjust spraying schedules accordingly.

Resistant Varieties

Grow these apple varieties that show resistance to cedar-apple rust:

Apple Variety Rust Resistance Level
Freedom High
Redfree High
Liberty Moderate
William’s Pride Moderate

These resistant varieties help reduce the need for fungicides and improve overall tree health.

Impact on Fruit Production and Plant Health

Damage to Leaves and Fruit

Cedar-apple rust, caused by the fungal pathogen Gymnosporangium juniperi-virginianae, significantly affects fruit production and the health of apple trees. It causes bright orange to red leaf spots on apples, hawthorns, and other plants in the Rosaceae family. The pathogen can infect leaves and fruit of susceptible cultivars and may lead to premature defoliation if the infection is severe.

Example:

  • A severe cedar-apple rust infection on an apple tree may result in less fruit production during the season.

Ornamental Value

The presence of cedar-apple rust on apple trees, crabapples, and other ornamental plants can decrease their aesthetic value due to the blemishes caused by this disease. While it’s not highly harmful to native Eastern red cedar and ornamental junipers, the appearance of rust spots can detract from their ornamental value.

Characteristics of affected plants:

  • Rust-colored spots or blemishes on leaves and fruit
  • Possible defoliation in severe infections

Effects on Plant Health

Cedar-apple rust is destructive to the overall health and vigor of affected apple trees. Premature defoliation and reduced fruit quality are common results of the disease. If severe infections occur for several consecutive seasons, it can lead to tree death.

Comparison table:

Healthy Tree Tree Infected with Cedar-Apple Rust
High fruit yield Decreased fruit production due to defoliation
Strong, vigorous growth Weakened growth and potential tree death
Clean, blemish-free fruit Rust-colored spots or blemishes on fruit

In conclusion, cedar-apple rust has a detrimental impact on fruit production and plant health. Preventing and treating the disease is crucial for maintaining the aesthetic and functional value of the affected plants. By staying informed and taking action, gardeners can protect their plants and minimize the damage caused by this fungal pathogen.

Frequently Confused Diseases

Cedar-Hawthorn Rust

Cedar-Hawthorn rust is caused by the fungus Gymnosporangium globosum. This disease infects members of the Rosaceae family like hawthorn, apple, and crabapple trees, as well as members of the Cupressaceae family, such as junipers. Some key differences between Cedar-Hawthorn rust and Cedar-Apple rust include:

Some examples of Cedar-Hawthorn rust symptoms include:

  • Leaf spots: yellow-orange with dark centers on hawthorn leaves
  • Fruiting bodies: spherical galls on junipers

Cedar-Quince Rust

Cedar-Quince rust, caused by the fungus Gymnosporangium clavipes, also infects the same groups of plants as Cedar-Hawthorn and Cedar-Apple. However, it mainly affects the twigs and fruit of hawthorns, and rarely on apples.

Characteristics of Cedar-Quince rust:

  • Orange, swollen, distorted twigs on hawthorn
  • Galls on junipers are longer and lack gelatinous spores
Cedar-Apple Rust Cedar-Hawthorn Rust Cedar-Quince Rust
Bright orange leaf spots Smaller, yellow-orange leaf spots Rarely on leaves
Prominent gelatinous spores Less prominent gelatinous spores No gelatinous spores
Affects mainly apple trees Affects mainly hawthorn Mainly on hawthorn twigs and fruit

Other Rust Infections

There are various other rust fungi that may lead to infections resembling the above-mentioned diseases. In such cases, it’s essential to closely examine the symptoms and the affected plants to make accurate diagnoses and apply appropriate treatments.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Goldenrod Gall Fly Gall

 

”in-line branch” bug pod – don’t know how to describe
Location: Lancaster, Pennsylvania
November 20, 2011 3:09 pm
Any idea what sort of insect grows inside these ”pods” on these shrub branches? When I cut them open there is a 1/4 inch ”grub” in the center.
They make great toy spinning tops.
Thank you for your time and your help!
Signature: cfunck

Goldenrod Galls

Dear cfunck,
This is a sight our editorial staff is quite familiar with having grown up in eastern Ohio.  Interestingly, this is the first submission we have received of Goldenrod Galls despite having this online column for more than 12 years.  These Galls
are formed by the Goldenrod Gall Fly, Eurosta solidaginis.  You may read more about this insect on BugGuidewhere it is stated:  “Larvae form round galls on the stem of certain goldenrods, Solidago. They feed there, then pupate in early spring. Adults emerge April-May and mate near goldenrod.”  Galls are growths on plants that are often caused by insects including flies, wasps and moths, and sometimes by mites.  Galls are abnormal growths that generally do not harm the plant, and though they are usually produced by insects and other arthropods, they can also be cause by other sources.

Goldenrod Gall

Daniel,
Thank you so much for this information!
Kind regards,
Chris Funck

 

Letter 2 – Cedar Apple Rust Gall

 

Subject: eggs on cedar tree
Location: north alabama
December 16, 2015 10:00 am
approx 3 inches accross found on limb of small cedar tree. Probably deposited sometime in October.
Signature: Olin

Cedar Apple Rust Gall
Cedar Apple Rust Gall

Dear Olin,
This Gall is an abnormal growth on a plant, and though many Galls are produced by insects, this Cedar Apple Rust Gall is caused by the fungus
Gymnosporangium juniperi-virginianae.  According to the University of Minnesota Integrated Pest Management for home apple growers page:  “Cedar-apple rust is a fungal disease that spends half of its life cycle infecting apple or crab apple trees, and the other half infecting Eastern Red Cedar (Juniperus virginiana) or other species of juniper (Juniperus sp.). This disease can cause damage to leaves and fruit of very susceptible apple varieties, but is only a minor problem on resistant or partially resistant trees.”  According to the Jack Schmidling Productions, Inc. site, your image:  ” is the gall that appears on the Cedar tree in late Winter. When this gall gets wet from Spring rains, the jelly masses emerge from the pores to ripen the spores. When the jelly dries, the spores are carried by the wind to apple trees.”

Letter 3 – Sumac Galls

 

What is it?
Mr. Bug Man,
Very cool website. Hope you can help. We have some Sumac trees in our backyard and some of them have these ‘sacks’ on them. They are attached to a leaf and seem to be feeding off of it. They are seemingly air tight, when you squeeze gently they are like a miniature air pillow. When taken apart there is a small cotton ball inside that is very air born and there are what look like seeds or eggs, yellowish in color, many of them. The sacks are various sizes and some are turning red like an apple would. Sure would appreciate your thoughts. Thank you,
Doug Cornelius
Deansboro, NY

Hi Doug,
These are Sumac Galls. According to BugGuide, the galls contain Aphid Colonies.

Letter 4 – Ocotillo with Galls?

 

Galls on Ocotillo?
Location: Organ Pipe Cactus National Monument, AZ
February 28, 2011 9:39 pm
My field crew and I came across this ocotillo that has what appear to be galls on it. Are these deformities produced by an insect, and if so, which one? Thanks!
Signature: Ed Kuklinski

Galls on Ocotillo?

Dear Ed,
According to the Morton Arboretum website:  “Galls are abnormal growths that occur on leaves, twigs, roots, or flowers of many plants. Most galls are caused by irritation and/or stimulation of plant cells due to feeding or egg-laying by insects such as aphids, midges, wasps, or mites. Some galls are the result of infections by bacteria, fungi, or nematodes and are difficult to tell apart from insect-caused galls. Seeing the insect or its eggs may help you tell an insect gall from a gall caused by other organisms.
”  What you have photographed does fall into the “abnormal growth” category, but we cannot say for certain that they were caused by insects.  The desert is a harsh climate, and there might be many things other than insects that might have caused this unusual phenomenon.  Perhaps one of our readers will provide some insight.

Galls on Ocotillo?

Letter 5 – Probably Galls on Cypress

 

Subject: Pink Eggs?
Location: Northeast Florida, riverside
August 6, 2014 11:03 am
Hello there,
My kids and I were examining a bald cypress at a local park last week, checking out the neat cones and leaves, when we noticed many of these pink pods randomly distributed all over the leaves. I’ve searched far and wide, but haven’t figured out what they are. Are they even bug eggs? I only figured they were because no readings on cypress trees mention any growths like these, and they were so randomly placed.
Thank you so much!
Signature: Alana

Probably Galls on Cypress
Probably Galls on Cypress

Dear Alana,
Your request has been on our back burner for a few days while we have attempted an identification.  Though these are not theoretically insect eggs, we do believe they are Galls.  Galls are growths on plants that are often caused by insects (mainly Gall Wasps and certain types of Flies and Moths) or Mites, but sometimes they are caused by viruses or other means.  Galls can form on any part of the plant, but are most common on leaves and twigs, but roots, stems and other parts of plants are not exempt.  See Texas A&M AgriLIFE Extension for some general information on Galls.  Your Galls look nothing like the Cypress Twig Gall Midge pictured on Featured Creatures, but there are probably thousands of different types of Galls that are found on oak trees.
  Your Galls are also different from the Cypress Gall Midges pictured on BugGuide.  Perhaps one of our readers will have better luck identifying the Galls you found on the cypress in your park.

Letter 6 – Cuckoo Wasp

 

Subject: Gall Insect
Location: Fairfield, California
March 28, 2016 1:40 pm
Hello Bugman!
I have a couple oak galls in a sealed bag and this morning, I found this brilliant green insect walking around on the exterior of one of the galls. I was not expecting to see such a beautiful insect since the gall wasps with which I am familiar are usually black! The galls were collected from the ground under an unidentified species of oak on March 23, 2016, in Fairfield, California. The insect is approximately 3/8 inch in length. Thanks for your help!
Signature: EntoMasterGardener

Possibly Pteromalid
Cuckoo Wasp

Dear EntoMasterGardener,
We are going to go way out on a limb in our response because of the interesting information we have learned while researching your request, and then we will consult Eric Eaton to see how far afield we have gone.  We tried researching green gall wasps and we stumbled upon an image that led us to a Nature Conservation Imaging where we learned the wasp in the image is a Pteromalid in the family Pteromalidae and that “The thousands of other parasitic wasps include the Chalcidoidea, which tend to be tiny and are often known as chalcids. There are more than 1,000 species in Europe including a good number of Pteromalid wasps (3mm). They are predominantly parasitoids, affecting a wide range of insect groups. A few are parasitoids of the larvae of gall wasps, so can emerge from galls, but they are not the causers.”  We then turned to BugGuide to see if we could find any visual matches, and we cannot say for certain that your Wasp resembles any definitively.  The antennae on your wasp are quite distinctive, and we will get back to you once we hear from Eric Eaton.

Eric Eaton sets us straight
Daniel:
Neither.  This is a cuckoo wasp, family Chrysididae.  They are parasites of other solitary wasps, and solitary bees, and perhaps one of the host insects nested inside an abandoned gall and the cuckoo wasp followed it inside.
Eric

Possibly Pteromalid
Cuckoo Wasp

Hi!
Thank you so much for your fast response! I think you are right on track! Through the awesome power of the Internet, my pictures found their way to UC Davis Professor of Entomology Robbin Thorpe and this was his response:
“The beautiful bright metallic green critter in the photos Sharon Leos submitted is a cuckoo wasp, family Chrysididae.  Most are parasitic on aculeate wasps and bees.  Some of which will nest in cavities like the emergence holes in oak galls.  Check out the family Chrysididae on Bug Guide for more illustrations.  For more information on the group, contact Dr. Lynn Kimsey, the Director of our Bohart Museum of Entomology.  Lynn is an expert on the group.  She should be able to identify the critter in more detail.  Lynn can be reached at: lskimsey@ucdavis.edu.  Regards,    Robbin”
I look forward to hearing what you learn from Eric Eaton, as well. Thank you so much! Have a great day!
Cheers!
~sharon

Letter 7 – Cedar Apple Rust Gall

 

Subject: Cocoon
Location: Westminster Maryland
April 3, 2016 10:43 am
In pine tree
Signature: Barry

Cedar Apple Rust Gall
Cedar Apple Rust Gall

Hi Barry,
This is not a cocoon.  It is a Gall.  According to Wayne’s Word:  “Galls are caused by many organisms living on plants, including insects, mites, mistletoe, fungi and bacteria.”  This marvelous website continues with “The mysterious origin of strange growths on the stems, leaves, flowers and roots of plants have intrigued naturalists for centuries. Called galls or hypertrophies, these tumorous (neoplasmic) outgrowths develop from rapid mitosis and morphogenesis of plant tissues and come in an astounding array of colors, shapes and sizes. Galls may be smooth, spiny or fuzzy, and resemble everything from marbles and ping-pong balls to dunce caps, saucers and sea urchins. Many galls provide the food and brooding structure for various species of harmless insects.”  The Propaedeuticist makes up in images what it lacks in information regarding your particular Gall, the Cedar Apple Rust Gall,
Gymnosporangium juniperivirginianae.  The Missouri Botanical Garden also refers to two additional, closely related species of fungus in stating:  “All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Of these alternate hosts, cedar-apple rust is primarily a disease of apples and crabapples. Cedar-hawthorn rust, in addition to affecting apples and crabapples, sometimes infects pears, quince, and serviceberry. Cedar-quince rust has the broadest host range and can infect many genera in the rose family. In addition to those plants already mentioned, mountain-ash, flowering quince, cotoneaster, chokecherry, and photinia are also hosts for this disease.”  Your tree is a cedar, not a pine.  The Missouri Botanical Garden site also states:  “Symptoms on juniper: Brown, perennial galls form on twigs. When mature (usually in two years), the galls swell and repeatedly produce orange, gelatinous telial horns during rainy spring weather. The galls of cedar-apple rust are often over 2 inches in diameter, while cedar-hawthorn rust galls are rarely over 2 inches in diameter. Occasionally the twig beyond the gall dies, but usually no significant damage occurs on the juniper host.”  If you or a neighbor has an apple orchard, there may be additional cause for alarm as the site states as the leaves of apple trees are affected, according to the Missouri Botanical Garden, when:  “Circular, yellow spots (lesions) appear on the upper surfaces of the leaves shortly after bloom. In late summer, brownish clusters of threads or cylindrical tubes (aecia) appear beneath the yellow leaf spots or on fruits and twigs. The spores associated with the threads or tubes infect the leaves (needles) and twigs of junipers during wet, warm weather.”

Fanmail June 22, 2017
Hey thanks!
The other day I came across your page here, where you linked to the Missouri Botanical Garden: https://www.whatsthatbug.com/category/attack-of-the-fungus/
So, couple things…
Thing #1: Thanks for the suggestion! I LOVE this garden but have never been. It inspired me to go learn a bit more about it. Which is why…
Thing #2: I also added that garden to a huge guide I wrote called “55 Stunning Botanical Gardens to See Before You Die.” Since you already mention the Missouri Botanical Garden on your page, I thought my guide would make a really good complement to your article if you wanted to add the link.
Here it is: https://www.sproutabl.com/gardening/botanical-gardens/
It would knock my socks off if you added it, but let me know what you think of the post in any case!
What do you think?
🙂  Winston

Hi Winston,
You may or may not want to put your socks back on.

Letter 8 – Hedgehog Gall

 

Subject: Strange Egg Sac
Location: Effingham, IL
September 10, 2016 7:19 pm
Hi,
I found this strange (what I believe is an) egg sac on a fallen leaf in Effingham, IL. I know you identify insects. Are you able to identify their eggs as well? Assuming this is an insect egg… Thanks!
Signature: Best, Jennifer

Spiny Oak Leaf Gall
Hedgehog Gall

Dear Jennifer,
This is a Gall, a growth appearing on a plant that might be caused by an insect, other arthropod or even an injury.  We found a very similar image on the Blue Jay Barrens blog, but the only information is:  “The oak leaves are developing some wonderful galls. I’m not sure how large these pea sized growths will eventually become.”  We found an image on Field Biology in Southeastern Ohio with the information:  “Spiny Hedgehog Galls. The yellow gum drop covered in red hairs makes this wasp
Acraspis erinacei. ”  Another similar image is on the Springfield Plateau blog and the name Hedgehog Gall is used.  Hedgehog Gall is also the name used on BugGuide and according to BugGuide:  “Forms galls on white oak (Quercus alba). The sexual generation forms galls on the buds, and the agamic generation forms the distinctive ‘hedgehog’ galls (ellipsoid, up to 13 mm in diameter, covered with red hairs, with 3-5 larval cells inside) on leaves. Females emerge from the leaf galls in the fall (October-December) and crawl to the buds to oviposit. The resulting gall is a thin-walled blister on the inner face of a bud scale, appearing as the buds start to open in the spring.”

Hi Daniel,
Thank you so much for sharing!  How incredibly interesting.  Nature is amazing.
Best,
Jennifer

Letter 9 – Maple Spindle Galls

 

Subject:  What is this??
Geographic location of the bug:  Buffalo, NY
Date: 08/30/2021
Time: 06:17 PM EDT
Your letter to the bugman:  What is this? Should I get rid of it? Is it dangerous?
How you want your letter signed:  Thank you, Lisa Wiest

Maple Spindle Galls

Dear Lisa,
We identified these a Maple Spindle Galls on Ohio State University Extension where it states:  “On sugar maple, another leaf gall is commonly found, the maple spindle gall. This gall is caused by the mite,
Vasates aceriscrumena (Riley). The gall appears as thin, elongate bladders arising from the upper leaf surface. These galls rarely distort the leaf, but considerable numbers of galls can make the leaves unsightly.”  Generally it is believed that Galls do not harm the plants upon which they are found.  According to BugGuide:  “Don’t cause serious damage but can be unsightly.”

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Goldenrod Gall Fly Gall

 

”in-line branch” bug pod – don’t know how to describe
Location: Lancaster, Pennsylvania
November 20, 2011 3:09 pm
Any idea what sort of insect grows inside these ”pods” on these shrub branches? When I cut them open there is a 1/4 inch ”grub” in the center.
They make great toy spinning tops.
Thank you for your time and your help!
Signature: cfunck

Goldenrod Galls

Dear cfunck,
This is a sight our editorial staff is quite familiar with having grown up in eastern Ohio.  Interestingly, this is the first submission we have received of Goldenrod Galls despite having this online column for more than 12 years.  These Galls
are formed by the Goldenrod Gall Fly, Eurosta solidaginis.  You may read more about this insect on BugGuidewhere it is stated:  “Larvae form round galls on the stem of certain goldenrods, Solidago. They feed there, then pupate in early spring. Adults emerge April-May and mate near goldenrod.”  Galls are growths on plants that are often caused by insects including flies, wasps and moths, and sometimes by mites.  Galls are abnormal growths that generally do not harm the plant, and though they are usually produced by insects and other arthropods, they can also be cause by other sources.

Goldenrod Gall

Daniel,
Thank you so much for this information!
Kind regards,
Chris Funck

 

Letter 2 – Cedar Apple Rust Gall

 

Subject: eggs on cedar tree
Location: north alabama
December 16, 2015 10:00 am
approx 3 inches accross found on limb of small cedar tree. Probably deposited sometime in October.
Signature: Olin

Cedar Apple Rust Gall
Cedar Apple Rust Gall

Dear Olin,
This Gall is an abnormal growth on a plant, and though many Galls are produced by insects, this Cedar Apple Rust Gall is caused by the fungus
Gymnosporangium juniperi-virginianae.  According to the University of Minnesota Integrated Pest Management for home apple growers page:  “Cedar-apple rust is a fungal disease that spends half of its life cycle infecting apple or crab apple trees, and the other half infecting Eastern Red Cedar (Juniperus virginiana) or other species of juniper (Juniperus sp.). This disease can cause damage to leaves and fruit of very susceptible apple varieties, but is only a minor problem on resistant or partially resistant trees.”  According to the Jack Schmidling Productions, Inc. site, your image:  ” is the gall that appears on the Cedar tree in late Winter. When this gall gets wet from Spring rains, the jelly masses emerge from the pores to ripen the spores. When the jelly dries, the spores are carried by the wind to apple trees.”

Letter 3 – Sumac Galls

 

What is it?
Mr. Bug Man,
Very cool website. Hope you can help. We have some Sumac trees in our backyard and some of them have these ‘sacks’ on them. They are attached to a leaf and seem to be feeding off of it. They are seemingly air tight, when you squeeze gently they are like a miniature air pillow. When taken apart there is a small cotton ball inside that is very air born and there are what look like seeds or eggs, yellowish in color, many of them. The sacks are various sizes and some are turning red like an apple would. Sure would appreciate your thoughts. Thank you,
Doug Cornelius
Deansboro, NY

Hi Doug,
These are Sumac Galls. According to BugGuide, the galls contain Aphid Colonies.

Letter 4 – Ocotillo with Galls?

 

Galls on Ocotillo?
Location: Organ Pipe Cactus National Monument, AZ
February 28, 2011 9:39 pm
My field crew and I came across this ocotillo that has what appear to be galls on it. Are these deformities produced by an insect, and if so, which one? Thanks!
Signature: Ed Kuklinski

Galls on Ocotillo?

Dear Ed,
According to the Morton Arboretum website:  “Galls are abnormal growths that occur on leaves, twigs, roots, or flowers of many plants. Most galls are caused by irritation and/or stimulation of plant cells due to feeding or egg-laying by insects such as aphids, midges, wasps, or mites. Some galls are the result of infections by bacteria, fungi, or nematodes and are difficult to tell apart from insect-caused galls. Seeing the insect or its eggs may help you tell an insect gall from a gall caused by other organisms.
”  What you have photographed does fall into the “abnormal growth” category, but we cannot say for certain that they were caused by insects.  The desert is a harsh climate, and there might be many things other than insects that might have caused this unusual phenomenon.  Perhaps one of our readers will provide some insight.

Galls on Ocotillo?

Letter 5 – Probably Galls on Cypress

 

Subject: Pink Eggs?
Location: Northeast Florida, riverside
August 6, 2014 11:03 am
Hello there,
My kids and I were examining a bald cypress at a local park last week, checking out the neat cones and leaves, when we noticed many of these pink pods randomly distributed all over the leaves. I’ve searched far and wide, but haven’t figured out what they are. Are they even bug eggs? I only figured they were because no readings on cypress trees mention any growths like these, and they were so randomly placed.
Thank you so much!
Signature: Alana

Probably Galls on Cypress
Probably Galls on Cypress

Dear Alana,
Your request has been on our back burner for a few days while we have attempted an identification.  Though these are not theoretically insect eggs, we do believe they are Galls.  Galls are growths on plants that are often caused by insects (mainly Gall Wasps and certain types of Flies and Moths) or Mites, but sometimes they are caused by viruses or other means.  Galls can form on any part of the plant, but are most common on leaves and twigs, but roots, stems and other parts of plants are not exempt.  See Texas A&M AgriLIFE Extension for some general information on Galls.  Your Galls look nothing like the Cypress Twig Gall Midge pictured on Featured Creatures, but there are probably thousands of different types of Galls that are found on oak trees.
  Your Galls are also different from the Cypress Gall Midges pictured on BugGuide.  Perhaps one of our readers will have better luck identifying the Galls you found on the cypress in your park.

Letter 6 – Cuckoo Wasp

 

Subject: Gall Insect
Location: Fairfield, California
March 28, 2016 1:40 pm
Hello Bugman!
I have a couple oak galls in a sealed bag and this morning, I found this brilliant green insect walking around on the exterior of one of the galls. I was not expecting to see such a beautiful insect since the gall wasps with which I am familiar are usually black! The galls were collected from the ground under an unidentified species of oak on March 23, 2016, in Fairfield, California. The insect is approximately 3/8 inch in length. Thanks for your help!
Signature: EntoMasterGardener

Possibly Pteromalid
Cuckoo Wasp

Dear EntoMasterGardener,
We are going to go way out on a limb in our response because of the interesting information we have learned while researching your request, and then we will consult Eric Eaton to see how far afield we have gone.  We tried researching green gall wasps and we stumbled upon an image that led us to a Nature Conservation Imaging where we learned the wasp in the image is a Pteromalid in the family Pteromalidae and that “The thousands of other parasitic wasps include the Chalcidoidea, which tend to be tiny and are often known as chalcids. There are more than 1,000 species in Europe including a good number of Pteromalid wasps (3mm). They are predominantly parasitoids, affecting a wide range of insect groups. A few are parasitoids of the larvae of gall wasps, so can emerge from galls, but they are not the causers.”  We then turned to BugGuide to see if we could find any visual matches, and we cannot say for certain that your Wasp resembles any definitively.  The antennae on your wasp are quite distinctive, and we will get back to you once we hear from Eric Eaton.

Eric Eaton sets us straight
Daniel:
Neither.  This is a cuckoo wasp, family Chrysididae.  They are parasites of other solitary wasps, and solitary bees, and perhaps one of the host insects nested inside an abandoned gall and the cuckoo wasp followed it inside.
Eric

Possibly Pteromalid
Cuckoo Wasp

Hi!
Thank you so much for your fast response! I think you are right on track! Through the awesome power of the Internet, my pictures found their way to UC Davis Professor of Entomology Robbin Thorpe and this was his response:
“The beautiful bright metallic green critter in the photos Sharon Leos submitted is a cuckoo wasp, family Chrysididae.  Most are parasitic on aculeate wasps and bees.  Some of which will nest in cavities like the emergence holes in oak galls.  Check out the family Chrysididae on Bug Guide for more illustrations.  For more information on the group, contact Dr. Lynn Kimsey, the Director of our Bohart Museum of Entomology.  Lynn is an expert on the group.  She should be able to identify the critter in more detail.  Lynn can be reached at: lskimsey@ucdavis.edu.  Regards,    Robbin”
I look forward to hearing what you learn from Eric Eaton, as well. Thank you so much! Have a great day!
Cheers!
~sharon

Letter 7 – Cedar Apple Rust Gall

 

Subject: Cocoon
Location: Westminster Maryland
April 3, 2016 10:43 am
In pine tree
Signature: Barry

Cedar Apple Rust Gall
Cedar Apple Rust Gall

Hi Barry,
This is not a cocoon.  It is a Gall.  According to Wayne’s Word:  “Galls are caused by many organisms living on plants, including insects, mites, mistletoe, fungi and bacteria.”  This marvelous website continues with “The mysterious origin of strange growths on the stems, leaves, flowers and roots of plants have intrigued naturalists for centuries. Called galls or hypertrophies, these tumorous (neoplasmic) outgrowths develop from rapid mitosis and morphogenesis of plant tissues and come in an astounding array of colors, shapes and sizes. Galls may be smooth, spiny or fuzzy, and resemble everything from marbles and ping-pong balls to dunce caps, saucers and sea urchins. Many galls provide the food and brooding structure for various species of harmless insects.”  The Propaedeuticist makes up in images what it lacks in information regarding your particular Gall, the Cedar Apple Rust Gall,
Gymnosporangium juniperivirginianae.  The Missouri Botanical Garden also refers to two additional, closely related species of fungus in stating:  “All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Of these alternate hosts, cedar-apple rust is primarily a disease of apples and crabapples. Cedar-hawthorn rust, in addition to affecting apples and crabapples, sometimes infects pears, quince, and serviceberry. Cedar-quince rust has the broadest host range and can infect many genera in the rose family. In addition to those plants already mentioned, mountain-ash, flowering quince, cotoneaster, chokecherry, and photinia are also hosts for this disease.”  Your tree is a cedar, not a pine.  The Missouri Botanical Garden site also states:  “Symptoms on juniper: Brown, perennial galls form on twigs. When mature (usually in two years), the galls swell and repeatedly produce orange, gelatinous telial horns during rainy spring weather. The galls of cedar-apple rust are often over 2 inches in diameter, while cedar-hawthorn rust galls are rarely over 2 inches in diameter. Occasionally the twig beyond the gall dies, but usually no significant damage occurs on the juniper host.”  If you or a neighbor has an apple orchard, there may be additional cause for alarm as the site states as the leaves of apple trees are affected, according to the Missouri Botanical Garden, when:  “Circular, yellow spots (lesions) appear on the upper surfaces of the leaves shortly after bloom. In late summer, brownish clusters of threads or cylindrical tubes (aecia) appear beneath the yellow leaf spots or on fruits and twigs. The spores associated with the threads or tubes infect the leaves (needles) and twigs of junipers during wet, warm weather.”

Fanmail June 22, 2017
Hey thanks!
The other day I came across your page here, where you linked to the Missouri Botanical Garden: https://www.whatsthatbug.com/category/attack-of-the-fungus/
So, couple things…
Thing #1: Thanks for the suggestion! I LOVE this garden but have never been. It inspired me to go learn a bit more about it. Which is why…
Thing #2: I also added that garden to a huge guide I wrote called “55 Stunning Botanical Gardens to See Before You Die.” Since you already mention the Missouri Botanical Garden on your page, I thought my guide would make a really good complement to your article if you wanted to add the link.
Here it is: https://www.sproutabl.com/gardening/botanical-gardens/
It would knock my socks off if you added it, but let me know what you think of the post in any case!
What do you think?
🙂  Winston

Hi Winston,
You may or may not want to put your socks back on.

Letter 8 – Hedgehog Gall

 

Subject: Strange Egg Sac
Location: Effingham, IL
September 10, 2016 7:19 pm
Hi,
I found this strange (what I believe is an) egg sac on a fallen leaf in Effingham, IL. I know you identify insects. Are you able to identify their eggs as well? Assuming this is an insect egg… Thanks!
Signature: Best, Jennifer

Spiny Oak Leaf Gall
Hedgehog Gall

Dear Jennifer,
This is a Gall, a growth appearing on a plant that might be caused by an insect, other arthropod or even an injury.  We found a very similar image on the Blue Jay Barrens blog, but the only information is:  “The oak leaves are developing some wonderful galls. I’m not sure how large these pea sized growths will eventually become.”  We found an image on Field Biology in Southeastern Ohio with the information:  “Spiny Hedgehog Galls. The yellow gum drop covered in red hairs makes this wasp
Acraspis erinacei. ”  Another similar image is on the Springfield Plateau blog and the name Hedgehog Gall is used.  Hedgehog Gall is also the name used on BugGuide and according to BugGuide:  “Forms galls on white oak (Quercus alba). The sexual generation forms galls on the buds, and the agamic generation forms the distinctive ‘hedgehog’ galls (ellipsoid, up to 13 mm in diameter, covered with red hairs, with 3-5 larval cells inside) on leaves. Females emerge from the leaf galls in the fall (October-December) and crawl to the buds to oviposit. The resulting gall is a thin-walled blister on the inner face of a bud scale, appearing as the buds start to open in the spring.”

Hi Daniel,
Thank you so much for sharing!  How incredibly interesting.  Nature is amazing.
Best,
Jennifer

Letter 9 – Maple Spindle Galls

 

Subject:  What is this??
Geographic location of the bug:  Buffalo, NY
Date: 08/30/2021
Time: 06:17 PM EDT
Your letter to the bugman:  What is this? Should I get rid of it? Is it dangerous?
How you want your letter signed:  Thank you, Lisa Wiest

Maple Spindle Galls

Dear Lisa,
We identified these a Maple Spindle Galls on Ohio State University Extension where it states:  “On sugar maple, another leaf gall is commonly found, the maple spindle gall. This gall is caused by the mite,
Vasates aceriscrumena (Riley). The gall appears as thin, elongate bladders arising from the upper leaf surface. These galls rarely distort the leaf, but considerable numbers of galls can make the leaves unsightly.”  Generally it is believed that Galls do not harm the plants upon which they are found.  According to BugGuide:  “Don’t cause serious damage but can be unsightly.”

Authors

  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

    View all posts
Tags: Plant Gall

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