Cottony Cushion Scale (Icerya purchasi) is an invasive pest that has long been a problem in the United States. Originally a pest of citrus plants in California, this scale insect has expanded its reach to feed on various ornamental plants such as Nandina, Euonymus, Boxwood, and Rose source. It is essential for gardeners, farmers, and horticulturists to be aware of Cottony Cushion Scale and its impact on plants.
Easily identifiable by their unique appearance, female Cottony Cushion Scales are rusty red with black legs and antennae, measuring around 4.5mm in length source. The males are smaller, around 3mm long, with a slender, reddish-purple body and metallic blue wings. Males also differ from females in that they have piercing and sucking mouthparts. The scale gets its name from the white, cotton-like wax it secretes when molting source.
As the Cottony Cushion Scale infests a plant, it can severely impact the overall health of the plant, often leading to stunted growth and even death. Thankfully, there are natural enemies like the vedalia beetle (Rodolia cardinalis) that help control the scale population. Both adults and larvae of these beetles feed on all stages of Cottony Cushion Scale, keeping their numbers in check source.
Overview of Cottony Cushion Scale
What Is Cottony Cushion Scale?
Cottony cushion scale (Icerya purchasi) is a pest that affects various plants, including citrus trees. Female cottony cushion scales are rusty red with black legs and antennae, measuring about 4.5mm long, while males are smaller (3mm) and reddish-purple with metallic blue wings. These pests have piercing/sucking mouthparts which can cause damage to plants.
Some key characteristics of cottony cushion scale are:
- Rusty red color in females
- Slender and reddish-purple appearance in males
- Cottony egg sac secreted by females
Icerya Purchasi Life Cycle
The life cycle of Icerya purchasi consists of several stages:
- Egg: Females lay 600-800 eggs within a cottony egg sac. Hatching can take a few days in summertime or up to 2 months in winter.
- Crawler: Newly hatched nymphs are red with dark legs and antennae. At this stage, they feed on plant tissues.
- Mature nymph and adult: The nymphs molt several times, leaving behind white, cottony molting skins. As they become adults, individuals differentiate into either female or male.
|Stage||Duration||Characteristics and behavior|
|Egg||Days to months||Laid within cottony egg sac|
|Crawler||Short period||Feed on plant tissues, red with dark antennae|
|Mature nymph and adult||Life span||Molting skins left behind, eventual adult differentiation|
The presence of cottony cushion scale on plants can be harmful, so proper management and control measures should be taken to protect them.
Damage Caused by Cottony Cushion Scale
Symptoms on Leaves and Twigs
Cottony cushion scale, a pest native to Australia, causes damage to various plants, including citrus trees and ornamentals 1. Symptoms include:
- Leaves: Curling, yellowing, and dropping off
- Twigs: Stunted growth and dieback
Fruit and Crop Damage
When cottony cushion scale infests fruit crops, it causes:
- Reduced fruit size and quality
- Deformed growths on fruit surfaces
- Premature fruit drop
This can directly impact crop yields and decrease market value.
Infestations and Dieback
Infestations of cottony cushion scale lead to several issues in the affected plants:
- High honeydew production: The scale insects excrete honeydew, which attracts ants and encourages sooty mold growth on leaves and fruit.
- Dieback: Due to their feeding on plant sap, heavy infestations can cause twig and branch dieback, and eventually lead to plant death.
|Honeydew||Attracts ants, encourages sooty mold|
|Twig dieback||Reduced plant vigor and growth|
|Branch dieback||Potential plant death|
Early detection and management of cottony cushion scale is crucial to minimize the damage caused to plants.
Cottony Cushion Scale Management and Monitoring
To manage Cottony Cushion Scale effectively, it’s crucial to monitor their population. These are some techniques:
- Visual inspection: Examine the plant’s twigs and branches for egg sacs, nymphs, and adults. Keep an eye out for white, cottony masses.
- Crawlers monitoring: Watch out for the nymphs, which are red with dark legs and antennae. They hatch within a few days in summer and up to 2 months in winter.
Sanitation and Pruning
Practicing sanitation and pruning can help control the scale population:
- Prune infested branches: If infestations are limited to specific parts of the plant, remove them to prevent spreading.
- Increase canopy exposure: In hot climates, pruning canopies open can reduce scale populations by exposing them to heat and parasites.
|Visual inspection||Non-invasive, no cost||Time-consuming, labor-intensive|
|Pruning||Reduces population, improves plant||Requires expertise, labor|
Cooperative Extension Resources
For more assistance and best practices, Cooperative Extension services are available to provide support and guidance. Reach out to your local county extension office for personalized advice on managing Cottony Cushion Scale in your area.
Interaction with Other Species and Environmental Factors
Ants and Honeydew
Cottony cushion scales secrete a sugary substance called honeydew. Ants are attracted to this honeydew, and they protect the scale insects from predators.
Some examples of these predators are:
- Green lacewings
Sooty Mold and Defoliation
The honeydew also promotes the growth of sooty mold. This black fungus affects plant aesthetics and can suppress plant growth. Defoliation may occur in heavily-infested plants.
Temperature and Reproduction
Reproduction in cottony cushion scales is influenced by temperature. Egg hatching may take a few days in summer, but up to 2 months in winter. Warmer temperatures accelerate their lifecycle.
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 – Cottony Maple-Leaf Scale: Pulvinaria acericola
Whats this bug?
The leaves of my Norway Maple are filled with these. A friend tells me they are Mealy Bugs but they are unlike any Mealy Bug I have ever seen or have been able to Identify. The white mass is approx. 1/4 – 3/8 inches long and has what appears to b a brown scale like "cap" at one end. Any help is greatly appreciated.
You have a type of Cottony Scale insect from the genus Pulvinaria whose members are characterized by a naked adult female (the scale) who excretes a large cottony egg-sac beneath or behind her body. The Maple-Leaf Pulvinaria, Pulvinaria acericola is found on maple leaves which your photo beautifully illustrates. You might want to try to control the outbreak by checking with a local nursery.
Letter 2 – Small Orange Bug on Citrus might be Cottony Cushion Scale
small orange bug
Location: Southern California
February 22, 2012 11:41 am
This guy came off a citrus tree in Southern California and is about 1mm in length. Other specimens from the same tree were greenish brown in color covered with a soot much like a mealy bug. I have this one under a microscope with shots top and bottom.
Signature: R. Japp
Dear R. Japp,
While we do not at this time know what this orange bug is that you found on your citrus tree, we don’t believe it to be a beneficial insect. We will take a bit more time to research this identification.
Karl poses a possible identification
Hi Daniel and R. Japp:
I am treading into unfamiliar territory here, but to me this looks a lot like an early instar Cottony Cushion Scale (Icerya purchasi). If that is the correct identification, it is considered a serious pest of citrus crops so there is a fair amount of information available on the internet. For example, you could check out this publication from the University of Arizona College of Agriculture, or this one from the University of California Division of Agriculture and Natural Resources. Here is a link to another set of photos that look quite similar. Although the topside colors are a little darker in this set, the black legs and antennae are apparently a key diagnostic feature for the species. The origin of this insect seems uncertain, possibly Australia, but it has now become global, living wherever citrus crops are grown. Regards. Karl
Letter 3 – Cottony Cushion Scale
Subject: garden bug
Location: Sacramento CA, USA
February 16, 2014 6:20 pm
I found these strangers on my neighbor’s miniature roses. It is February now, and the location is Sacramento, CA, USA. They were on other plants, but seem to prefer roses. they are about the size of a large, fat grain of cooked rice. Picture P2140190 is on the miniature rose from above, and picture P2140192 is the underside of one of them. The white area is fibrous and kind of fluffy.
Signature: Lily Tee
Dear Lily Tee,
This looks like a Cottony Cushion Scale, Icerya purchasi, to us. According to BugGuide, it is also called “Fluted Scale, Australian Bug, Australian Mealybug.” This introduced species poses a major threat to citrus trees as well as many other cultivated plants. BugGuide also notes: “The white fluted part of the insect is an egg sac that can contain up to 1000 eggs. The insect is hermaphroditic, producing sperm that can fertilize its own ova, but in an alternate reproductive strategy it can also make winged males that can fertilize the female part of other individuals. When it first appeared in the w. US it was a major pest of Citrus crops. In CA, around 1889, it was an early success story for biological control by beneficial ladybird beetles (Rodolia cardinalis). (Full story) The control was so successful that in 1893 a Florida nurseryman asked for some of the beneficials to be sent to FL, to test as a control for other scale insects. The scale was included in the shipment as food for the beetles, and thus accidentally introduced to FL citrus.” Your images are quite excellent in detail.
Thank you so much for your quick response! I will get my friend some lady bugs (and some for me as well).
Letter 4 – Cottony Cushion Scale
Possible scale on Euphorbia
January 2, 2010
I was doing some pruning and came across these crazy scales (?) on one of my evergreen Euphorbias. There were eggs and then the next stage appeared to be a reddish brown insect that looked similar to a roly poly but flatter. Then it develops into a scale looking insect with crazy toothpaste white stuff underneath it. It appears to leave behind a tube of scalloped toothpaste stuff. What the…?
You have nailed the ID. This sure looks like a Cottony Cushion Scale, Icerya purchasi, to us. According to BugGuide, on this Australian native: “The white fluted part of the insect is an egg sac that can contain up to 1000 eggs. The insect is hermaphroditic, producing sperm that can fertilize its own ova, but in an alternate reproductive strategy it can also make winged males that can fertilize the female part of other individuals.“
January 3, 2010
I sent an e-mail on January 2nd regarding scales. I was able to get some better photos and thought I would forward them along. They show the several stages described in my e-mail.
Letter 5 – Cottony Cushion Scale
Subject: Giant mealybug ? Scale?
Location: Glendale, California, USA
April 9, 2013 9:30 pm
Greetings Bugman – It is windy indeed around the corner here in Glendale!
Yesterday I removed the ties around a wood stake that was supporting a newly planted albizia tree in my backyard. Bright orange, egg-yolk-looking stuff smeared on my fingers and I found little groupings of these creatures beneath several of the ties.
They look like mealybugs, but they are huge! A quarter of an inch long, at least. Can you identify them? Are they beneficial, destructive, or neutral?
Thanks in advance.
Signature: Janine in Glendale
It is currently calm, but we understand the winds are supposed to return today. We believe these are Cottony Cushion Scale, and we believe that is the insect we found on our endangered California Black Walnut last year. When we manually smashed them, they were orange. You can read about the Cottony Cushion Scale on BugGuide where it states: “Hosts include many plants, though in FL Citrus and Pittosporum are most commonly affected.” The University of Florida Featured Creatures states: “The mature females (actually hemaphrodites) have bright orange-red, yellow, or brown bodies (Ebeling 1959). The body is partially or entirely covered with yellowish or white wax. The most conspicuous feature is the large fluted egg sac, which will frequently be two to 2.5 times longer than the body. The egg sac contains about 1000 red eggs (Gossard 1901).” You should try to eliminate the Scale. According to the Featured Creatures: “The cottony cushion scale can severely damage trees, resets, and nursery stock. Decreased tree vitality, fruit drop, and defoliation result from the feeding of this scale. Most damage occurs from the feeding of the early immature stages of the scale on the leaves, where they settle in rows along the midrib and veins, and on the smaller twigs. The older nymphs continue to feed, but migrate to the larger twigs, and finally, as adults, they settle on the larger branches and trunk. This scale is seldom found on the fruit. Added damage can result from the accumulation of sooty mold due to the honeydew excreted by the scale.”
Thank you so much :). Off on scale safari I go. Janine
Letter 6 – Cottony Cushion Scale
Subject: Strange Looking
Location: San Antonio, TX
September 13, 2013 5:42 pm
Hi Bugman! I have no idea what these are but I found them on my lime tree here in San Antonio, TX. There are about 8 of them in a bunch and only on one branch of the tree. I cut the branch off to prevent a further infestation. Any ideas?
These are Cottony Cushion Scale, Icerya purchasi, and you were wise to remove the branch. According to BugGuide, it is “Native to Australia, has spread widely as a crop pest” and “When it first appeared in the w. US it was a major pest of Citrus crops. In CA, around 1889, it was an early success story for biological control by beneficial ladybird beetles (Rodolia cardinalis). (Full story) The control was so successful that in 1893 a Florida nurseryman asked for some of the beneficials to be sent to FL, to test as a control for other scale insects. The scale was included in the shipment as food for the beetles, and thus accidentally introduced to FL citrus.”
Letter 7 – Cottony Cushion Scale
Subject: Very weird white bugs
Location: San Jose, California, US
October 14, 2013 11:49 am
My daughter found those little guys on a bush near our home. Initially I didn’t even recognize them as bugs – they looked that strange. I searched all over the net for ”weird white bugs”, ”white and brown larvae”, and anything else I could think of, but as you can probably guess this didn’t help at all…
Any idea what this might be – can you point me in the right direction?
The good news is we can identify your bug, and the bad news is that you have an infestation of Cottony Cushion Scale. For advice on how to control the Cottony Cushion Scale, you can try the UC Davis Integrated Pest Management System where it states: “Cottony cushion scale, Icerya purchasi, can infest a number of woody ornamentals and certain crops (Figure 1). Common hosts in California are citrus, cocculus, nandina, and pittosporum. Its cottony egg sac and profuse honeydew production make cottony cushion scale easy to spot in the landscape.”
Letter 8 – Cottony Cushion Scale
Subject: White bugs on heavenly bamboo
March 25, 2014 12:14 pm
These creatures are all over my heavenly bamboo, particularly on the top third of the branches. They hang out on the underside–they appear to be hanging on by legs and a mouth, but my mom thinks they are a chrysalis. The front of them is a brown or maybe an orange/black. We picked a few off thinking they were a pest before thinking maybe they’re good bugs–what are they? It’s an unseasonably warm/dry spring in Sacramento, CA.
You have an infestation of Cottony Cushion Scale, a pest species from Australia that has become established in North America where it is a significant crop pest. According to BugGuide: “The white fluted part of the insect is an egg sac that can contain up to 1000 eggs. The insect is hermaphroditic, producing sperm that can fertilize its own ova, but in an alternate reproductive strategy it can also make winged males that can fertilize the female part of other individuals.
When it first appeared in the w. US it was a major pest of Citrus crops. In CA, around 1889, it was an early success story for biological control by beneficial ladybird beetles (Rodolia cardinalis). (Full story) The control was so successful that in 1893 a Florida nurseryman asked for some of the beneficials to be sent to FL, to test as a control for other scale insects. The scale was included in the shipment as food for the beetles, and thus accidentally introduced to FL citrus.
Thank you so much! 1000 eggs! Really? Eeek–I’m not a “bug man”–my skin is crawling. I appreciate the info.
Letter 9 – Cottony Cushion Scale
Subject: White pupae?
Location: Portsmouth, VA
November 13, 2015 9:20 am
Good morning from Tidewater area, Virginia.
I found these white pupaeish looking things on an ornamental bamboo plant outside the hospital parking garage. At first I thought they were bird poop but the clusters looked less planned.
Are they moths-in-training perhaps?
Signature: Dia from Chesapeake
These are Cottony Cushion Scale insects, Icerya purchasi, and you can compare your image to this image on BugGuide. According to BugGuide: “The white fluted part of the insect is an egg sac that can contain up to 1000 eggs. The insect is hermaphroditic, producing sperm that can fertilize its own ova, but in an alternate reproductive strategy it can also make winged males that can fertilize the female part of other individuals. When it first appeared in the w. US it was a major pest of Citrus crops. In CA, around 1889, it was an early success story for biological control by beneficial ladybird beetles (Rodolia cardinalis). (Full story) The control was so successful that in 1893 a Florida nurseryman asked for some of the beneficials to be sent to FL, to test as a control for other scale insects. The scale was included in the shipment as food for the beetles, and thus accidentally introduced to FL citrus.”
Letter 10 – What's That Scale? Could it be Cottony Cushion Scale on endangered California Black Walnut????
December 4, 2010
Today when the gardening crew came to lay down more decomposed granite in the front yard of our Mt Washington offices, I noticed this Scale Insect on several twigs of the California Black Walnut sapling that grew in the Devil’s Strip next to the fence. When I went back to take the photograph, it had been pruned and left in the street by Paco the Gardener. I took the photographs. These Scale insects look suspiciously like the Cottony Cushion Scale, Icerya purchasi, (See BugGuide) that was introduced from Australia and nearly devastated the citrus crop after its introduction in around 1868.
This identification is going to be our top priority as we are quite committed to saving the endangered California Black Walnut in Southern California, and most aggressively in the Mt Washington neighborhood of Los Angeles.
Update: December 5, 2010
An internet search turned up a Google Book entry on Pests of Crops in Warmer Climates and Their Control by D.S. Hill and it indicates that the Cottony Cushion Scale can be found on English Walnut, Juglans regia, so it might be safe to assume that it may also be found on California Black Walnut, Juglans californica.
Clare Marter Kenyon wrote
ugh. no. i don’t recall seeing this scale on juglans californica…
get rid of it pronto!