- How to Get Rid of Thrips on Roses
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- OPTIMAL CONDITIONS
- GOOD GUY / BAD GUY?
- Systemic Insecticide for Houseplants
Thrips are a type of invisible plague to roses and many other ornamental and even fruit and vegetable plants!
They can be tough customers to get rid of once they have invaded your roses – but with the right advice and by spraying with effective insecticides it can be done.
Visible damage to the the petal edges.
To control thrips, it is essential to add an insecticide to every spray cocktail, and to spray thoroughly in order to make good contact with the larvae or insect. The smell of garlic contained in Ludwig’s Insect Spray is a deterrent to thrips.
When: Prevalent in drier periods, but can occur any time of the year.
Where: country wide / world wide
Remedy: Apply Koinor as a drench in September. Watch this video on how to apply Koinor. Alternate with including Cyper and Plant Care into your spray cocktails. It is important to spray thoroughly in order to make good contact with the larvae and insect on the leaves and in the blooms. The smell of garlic contained in Ludwig’s Insect Spray which is the main ingredient of our main Cocktail is a deterrent to thrips. However if you see the damage to your roses you need to include the above named insecticides into the mix.
Frequency: Weekly over three weeks if you can see visible damage. A regular spray program preventatively keeps thrips at bay.
Effect on plant: Damage to bloom as petals take on an ugly appearance as the chew marks and scars become pronounced when the petals unfold. Damage to young growth so that leaves clearly looked deformed and shrivelled up.
Info: Thrips are tiny, winged insects that settle between the petals of tight buds and start rasping the petal edges.
They can damage the petals of each bloom on the plant. The damage is more visible on lighter coloured roses. Serious damage includes the deformation of young leaves and growth.
The breeding cycle stretches from eggs that develop in the soil, through two larval stages on the leaves, to the mature insect in the flower.
They are able to fly and are easily carried by the wind.
Other plants and weeds may act as host plants from which they easily fly or blow into your roses.
Roses are one of their delicacies. You can imagine them to be to plants what mosquitos are to humans.
Alternative combat: none
If no action is taken: Blooms look “ugly” and leaves may look deformed. Rose does not perform as it should.
This blemish was caused by thrips before the sepals opened.
Thrips damage on the yet to open bud.
Thrips damage to bud and within the bloom.
Thrips punctured the very immature leaves causing curling.
Thrips damage severe and unchecked! They chew away on both sides of the leaves. The marks seen are scar formation.
After spraying the new leaves are free of any thrips damage.
THRIPS – article by Alan Brimer
As a language person I’m entertained by the fact that the singular and plural forms of the word ‘thrips’ are the same: one thrips, two or more thrips! There can’t be many words like that in the English language. As interesting as that may be, it’s irrelevant to what happens in the garden.
Some of our members have phoned me recently (I’m writing this in mid September) and asking me to tell them why the new foliage on their rose bushes is gnarled. (Telephonic diagnoses are hit and miss affairs. I’d rather avoid them.) I myself have a bad infestation of thrips in my own garden, and stupidly failed to make a connection between what’s happening in my garden and what might be happening in our members’ gardens. Sorry! It’s possible that you may have thrips too.
If in your garden you find a gnarled young bloom with brownish blotches on the petals, snap it off the cane, take it inside the house, turn it upside down over a bright surface such as a sheet of white paper, ands give it a smart rap. If you’ve got thrips they will fall out of the bloom onto the paper, where you will see a number of minute elongated winged insects walking about aimlessly. Thrips!
This is a diagram of the Western Flower Thrips, which is the variety we’re likely to have in our gardens. There are actually about 6000 different sorts of thrips in the world, but this is the one that particularly likes roses. Of course, this is a huge magnification. The actual insects are no more than 1mm or 2 mm in length. The females are amber or yellowish-brown to dark brown in colour, and the males are a bit smaller and are light yellow. Both genders have serated wings and piercing mouths. They feed on pollen and on the sap of petals, which they extract by sucking or by vibrating their wings in between the closely compressed petals, thus damaging them and causing them to exude sap. This causes the brown blotches on the blooms. They also feed on young foliage, slashing the surface and sucking the contents of the cells, distorting the growth as the leaf tissue expands, and causing the plant to produce blind shoots rather than buds. Damaged leaves may be puckered and twisted.
Females insert eggs into succulent host plant tissue, the eggs develop into two successive larval stages, then into pupae, and then into adults. The process takes about 13 days in ordinary weather. (It’s faster in hotter weather and slower in colder weather.) Adults live about 28 days and lay an average of 44 eggs!
Some of the literature advises that you plant garlic among your rose bushes or spray with a garlic-impregnated oil for various reasons including the possibility that it will disguise the perfume of the roses and so keep the various insect pests from finding them. I don’t know if that works or not but it’s certainly not going to help if you already have an infestation.
I’ve had no success whatsoever in my attempts to get rid of my thrips, and as I write this I’m worrying about whether or not I’ll have any blooms to exhibit at our Spring Show. The reasons why thrips are virtually impossible to get rid of are because their lurking places in between the petals of tight flower or leaf buds shelter them from contact insecticides, because they’re immune to many systemic insecticides, and because they build up immunity to contact insecticides rather quickly. But even if we can’t get rid of them altogether, we may be able to control them successfully.
We may or may not! I’ve tried just about everything that one is advised to do, without success, and now I’m going to have to try again, but as always with a slight difference. Reading most of the literature on the web and everything my books say about this topic, I think the thing to do may be to try to interrupt the life cycle of the insects (as one has to do with white-fly and red spider-mite). Weather and time permitting, I’m going to spray every five days for two or three weeks, varying the insecticide, and lacing it with sugar (Esther Geldenhuys’ tip, which is echoed in some web pages) to try to lure the insects out of their hidey holes. As thrips don’t feed until they reach the pupal stage, it’s possible that I have in the past wiped out successive generations of the creatures, only to have them continuously replaced by the next generation in line – which might be the explanation for my thinking that all of my spraying was having no effect.
I’ll keep you posted about whether or not this succeeds. Meanwhile, why don’t you try the trick with the sheet of paper? You might be surprised by what you see!
How to Get Rid of Thrips on Roses
As rosarians eagerly anticipate their first rose blossoms of the growing season, a common garden pest may disrupt the beautiful rose display. Thrips, tiny winged insects that gorge on blossoms and leaves, prefer light-colored roses and often make their presence known in a garden by causing unsightly brown blemishes on the rose blossoms or even preventing them from opening. Get rid of thrips on roses to stop the infestation and protect future blossoms.
Watch your roses carefully to notice a thrip infestation as quickly as possible. If you see blossoms that swell but do not open or if you notice blossoms with discolorations on the petals, this indicates thrips on your roses. You may also see distorted leaves if you have thrips on your roses. Act swiftly to get rid of the thrips.
Cut off all plant portions with thrip damage. Use the pruning shears to remove all blossoms, leaves and stems where you see evidence of thrips.
Place these removed portions of the rosebush into a plastic bag and seal the bag tightly. By removing the portions of the plant and sealing them into the bag, you can effectively remove adult thrips and nymphs.
Sprinkle systemic insecticide over the soil beneath the rosebush. Use approximately half a cup of granules to cover the soil evenly. This kills pupa thrips that are developing in the soil. If you do not eradicate these thrips now, they move up out of the soil and onto the rosebush within a few days.
Spray the rosebush with insecticide at the same time that you apply the granular insecticide to the soil. Cover the entire plant completely. Repeat the spray application once per week throughout the growing season to interrupt the life cycle of surviving thrips.
Continue watching the rosebush for evidence of thrips. Remove any portions of the plant that appear to have thrip damage.
Thrip are a tiny insect around 2mm long, they vary in colour from yellow to black and come into your garden on the wind. They will normally come in on hot dry weather in Spring or Summer and are attracted to light colours, they often can be seen on white sheets hanging on the line.
Thrip feed by draining the contents of plant cells, this will cause white specks or trails on new leaves and scarring on petals which are often seen as brown blemishes on light coloured blooms. Most people notice the effects on pale coloured flowers first leaving blooms with brown edges which is often mistaken for water rot. If left they can be quite destructive and often cause deformities in new growth.
The first thing to try is your hose – they hate water. If a small infestation or you have just noticed the signs then spraying the rose plant with water from your hose discourages them from settling and they will soon move on. Remember to spray both under and over the leaves.
Cut off all badly affected blooms.
Encourage natural predators such as: bugs, ladybirds, lacewing larvae, mites and predatory thrips.
Remove weeds to reduce breeding sites.
Try using a garlic or chilli spray. Take two teaspoons of crushed garlic or chilli and put into 500mls of water. Let this sit for a couple of days so the water is very potent. Strain and spray onto the plants. Although this home remedy is highly effective it will need to be repeated each week for a couple of weeks or after it has rained.
It may be necessary to spray roses with an insecticide or Eco Oil. Remember that the thrip also lay eggs on the plant and a repeat spray may be necessary a couple of weeks after the first. Please use chemicals sparingly as they also kill the good insects and natural predators as well as the one you are trying to get rid of – always look for a natural alternative before using chemicals!
Thrip have a short life cycle, having many gererations in one year. Therefore the chemical sprays on the market are a bit of a hit and miss as thrip become very resistant to most chemical sprays.
Remember that whatever treatment you decide on will have to be re-applied in a couple of weeks when the eggs laid by the first infestation hatch.
For a long term solution try companion planting your roses with Lavender, Garlic, Chilli, chives or marigolds. This will help to protect your roses from future attacks.
Important: signs and symptoms will vary significantly between varieties, even within similar categories. The information provided here is a basic summery of the most common affects and will not always be applicable to all rose varieties.
by Nanette Londeree, Master Rosarian
Tiny, slender adult insects, less than 1/20 inch long, translucent white or yellowish to dark brown or blackish with long fringe around the margins of their wings
Larvae similarly shaped with a long, narrow abdomen and no wings
Stippling on leaf surfaces that may become papery
Black specks of feces around stippled leaf surfaces
Flower buds that are deformed and fail to open
Petals covered with brown streaks and spots
Distorted plant parts
One of the species of Thrips, order Thysanoptera, most often Western Flower Thrip (Frankliniella occidentalis)
Many herbaceous ornamentals (impatiens, petunia); vegetables (cucurbits, pepper); fruits (grape, strawberry); some shrubs and trees (rose, stone fruit)
Prefer to feed in rapidly growing tissue
Spring to early fall; lifecycle may be as short as two weeks during warm weather
Maintain good cultural practices and plant to attract natural enemies like green lacewings and minute pirate bugs
Keep plants well irrigated and avoid excessive applications of nitrogen fertilizer that may promote higher populations of thrips
Control nearby weeds that are alternate hosts of certain thrips
Select cultivars with sepals that remain tightly wrapped around the bud until just before blooms open
Knock pests off plants with a spray of water
Damage to leaves and blooms may be unsightly but does not usually warrant the use of insecticide sprays
No pesticide provides complete control due to thrips’ tiny size, great mobility, hidden feeding behavior, and protected egg and pupal stages
Narrow-range oil (Sunspray, Volck) and neem oil can be somewhat effective for temporary reduction of populations if applied when thrips are present and damage first appears
GOOD GUY / BAD GUY?
A bad guy if you exhibit roses; mostly a nuisance otherwiseThe photo of Thrips at the top of the page is by Baldo Villegas from the extraordinary website: http://members.tripod.com/buggyrose/irosepests.htm
How to Get Rid of Thrips
- To keep thrips populations under control, try using yellow or blue sticky traps.
- Shaking branches to remove the thrips and catching them on a cloth underneath is one easy way to quickly remove the thrips from your plants.
- For onion thrips: Take a dark piece of paper into the garden and knock the onion tops against it; if thrips are present, you will spot their tan-colored bodies on the paper. A couple of treatments with insecticidal soap kills them. Follow the package directions. Spray the plants twice, three days apart, and the thrips should disappear.
- For fruit trees: Spray dormant oil on the trees.
- As a last resort, dust the undersides of leaves with diatomaceous earth.
Photo credit: Steven Arthurs/University of Florida. Black thrips and thrip damage on a fig tree.
How to Prevent Thrips
- For flower thrips on gladiolus: Mix 1 tablespoon Lysol household cleaner with 1 gallon water. Soak gladiolus corms in the liquid and plant while still wet to prevent thrips.
- You can plant various flowers to attract beneficial insects that are natural predators to thrips. Some good predators include pirate bugs, lacewings, and lady bugs. Learn more about attracting those predators.
- For onion and western flower thrips, try releasing minute pirate bugs or the predatory mite Amblyseius cucumeris.
- Reflective mulches can help to hide your plants from thrips.
- If there is a very big thrips problem in your area, some plants have resistant varieties.
- Try not to overfertilize plants, as this can lead to more thrips damage.
Do you have more tips for controlling thrips? Let us know below!
Systemic Insecticide for Houseplants
House Plant – Croton image by evillager from Fotolia.com
Houseplants can be just as susceptible to insect infestations as outdoor plants, and it’s just as important to control these infestations. Systemic insecticides can be particularly effective against a number of pests, but the first step is to correctly diagnose the source of the damage visible on the plant.
cactus image by Zagorizont from Fotolia.com
Systemic insecticides are a group of insecticides that are applied to the soil of the houseplant, and then absorbed through the roots. The insecticide then travels through the plant without harming it. The active and inactive ingredients settle into the tissues of the plant, and when it is ingested it is enough to kill or deter the insect feeding on the plant.
Because systemic insecticides are absorbed into the tissues of the plant itself, they are effective against a different kind of pests. While a number of insects, identified by their chewing mouthparts, eat the leaves of the plant and are killed or deterred by insecticides that are applied topically, there is another type of pest. These have mouthparts not made for chewing, but for sucking the nutrients out of the tissues of the plant. Since these pests don’t eat the leaves, they are unaffected by topical insecticides and must be killed by internal pesticides.
The active ingredients in systemic insecticides, which vary by product, are often too toxic to handle by themselves. In order to make them safe to be applied to houseplants, they are often mixed with other ingredients called adjuvants. There are a number of different ingredients that can be used, from vegetable oil to ground walnut shells. Combinations of active ingredients and adjuvants are closely guarded secrets and considered proprietary information. On the label of the insecticides, they are typically referred to as inert ingredients. Systemic pesticides are typically in granule form, pellet form, or soluble solutions.
Systemic insecticides can be administered to control a variety of different pests. One thing all these pests have in common is how they feed: by sucking nutrients from the tissues of the houseplants. One of the most common household pests that are fought with systemic insecticides is mites. They are not usually used on insects and pests that chew leaves; looking at the leaves of the infected plant will tell what kind of insect is infecting it.
Fresh parsley over white image by Olga Chernetskaya from Fotolia.com
Systemic insecticides are not generally used in any plant that will be used for human ingestion. The active ingredients remain in the parts of the plant, and while some systemic insecticides are safe for animals to ingest, they aren’t used on human foods. For houseplants, this means herb gardens and window sill tomatoes are off-limits for systemic insecticides.
Deformed and discolored blooms indicate a chilli thrips infestation. The rose in the foreground is Marilyn Monroe. Photo – Rita Perwich
Presence of near-invisible chilli thrip detected by deformed, discolored blooms
By RITA PERWICH (This article first appeared in the San Diego Union-Tribune on April 4, 2019)
When I was a child, I was scared of the jabberwocky and other similar monsters. I outgrew those fears, but I am presently filled with even greater anxiety about chilli thrips, a pest that arrived in many gardens in San Diego last summer and is likely to be a big problem this year. You have been warned. Be on the look out for damage daily.
Here is what you need to know about chilli thrips:
Identifying chilli thrips: This is an enemy we can’t see with the naked eye. Chilli thrips are very small, only 0.016 to 0.024 of an inch in length, which is about one-quarter the size of western flower thrips. You will know you have chilli thrips in the garden only when the new foliage and blooms on your roses are already damaged. Rose blooms will be deformed and discolored, and the outer petals will be darkened. Buds will be distorted and may not even open. Unlike the western flower thrips, which favor mainly light-colored blooms, chilli thrips don’t have a preference. They love all bloom colors. And unlike the western flower thrips, chilli thrips aren’t satisfied with just the buds and blooms. They attack the fresh new foliage. You will see misshapen and distorted new foliage and bronzing on the back of the new leaves. The amount of damage they can do in a very short time is astounding! It is imperative to notice the earliest stages of an attack upon your rosebushes since a severe infestation of chilli thrips can defoliate a rose plant rapidly. And while you are out checking your roses, check your other plants, too.
Misshapen and distorted new foliage and bronzing on the back of the new foliage exhibit the rasping damage caused by chilli thrips. Photo: Baldo Villegas
Host plants: Chilli thrips don’t limit themselves to roses. They are known to attack many other ornamental plants in the garden such as begonias, jasmine and chrysanthemums. Fruits they attack include strawberries, blueberries, kiwis, grapes, mangos and citrus. In your vegetable garden, keep watch on your tomatoes, beans, chilies and peppers. This pest also attacks crops such as soybeans, tobacco, corn, tea, cocoa and cotton. Scientists believe chilli thrips originated in Asia. They were first detected in the United States in Florida on roses in Palm Beach in 2005. They made their way through the southern states and by 2008 were well established in Texas. Chilli thrips were first confirmed in California on residential roses in Anaheim in 2015.
Life cycle: The life cycle stages of chilli thrips include a microscopic egg which is laid by the adult inside plant tissue, a first and second instar larvae and a prepupa and pupa. The larvae and adults are the only feeding stages. Both the young and mature thrips use piercing and sucking mouthparts to extract sap from young leaves, buds and blooms. When the second instar larvae are ready to molt into the pupal stage, they usually enter the soil or litter beneath the rose plant. After prepupal development is completed, the insect molts into the pupal stage. The adults do not technically fly but are capable of dispersal by wind over long distances as they have a dense fringe of long hairs on slender wings. They are a year-round pest but are less destructive during cool and wet weather mainly because in hot weather they reproduce quickly from egg to egg in 11 days. In cooler weather the life cycle, from egg to egg, takes approximately 40 days.
Control: Integrated Pest Management stresses the importance of cultural, mechanical and biologic controls before resorting to the use of the least toxic chemical controls. In all the years I have been growing roses by following the cultural, mechanical and biologic controls of IPM, I have not needed to get to the last rung, that of chemical control. This may have to change, as I am told by Bob Martin, master rosarian and president of the American Rose Society, and Tom Carruth, renowned hybridizer and curator of the Huntington Garden, that an infestation of chilli thrips cannot be wiped out without the use of chemicals. Since the complete life cycle for chilli thrips can occur in less than two weeks’ time, you must detect damage and implement a method of control right away.
Start with the preventive controls — cultural, mechanical and biologic. Monitor the rose garden daily. You must cut out damaged buds, blooms and leaves. Remove all fallen leaves and petals out of the garden immediately as part of the life cycle of this pest enters the soil or litter beneath the rose plant. The champion and hero in the fight against chilli thrips in our gardens is the minute pirate bug, which feasts on all the life stages of this pest. The good news for the future is that researchers are having success with two biologic controls: a predatory mite, which has shown effect in greenhouses in controlling the larval stage of chilli thrips, and nematodes that parasitize female thrips and make them incapable of laying eggs.
Chemical controls: If this becomes necessary, choose the least toxic spray, and read and follow the label. During an infestation, the new growth will need to be sprayed weekly. Conserve or Captain Jack’s Deadbug Brew Concentrate are two organic sprays that are used to eradicate chilli thrips. Their active ingredient, Spinosad, will not harm ladybugs, green lacewings, minute pirate bugs and predatory mites. But use great caution, as it will harm bees if it comes in contact with them. Always take the precaution of spraying very early in the morning or in the evening, after the bees are done working for the day.
There is a saying, “the garden grows best when the shadow of the gardener is there frequently.” This is especially true with chilli thrips. Your alert attention will make all the difference.
Perwich is a member of the San Diego Rose Society, a Consulting Rosarian and a Master Gardener with UC Cooperative Extension.
Adult chilli thrips. Photo: Andrew Derksen, USDA-APHIS, Bugwood.org
Article author: Scott Ludwig, Carlos Bogran
Most recently reviewed by: Erfan Vafaie (2018)
Common Name(s): Chilli Thrips
Landscape Ornamental, Greenhouse Ornamental and Nursery, Vegetable and Fruit
Chilli thrips are extremely small and difficult to distinguish from other thrips species without the aid of a compound microscope. Adults are pale with dark wings and less than 2 mm in length. Immature chilli thrips are also pale in color and resemble the immatures of many other thrips species. Infestations by chilli thrips are usually first detected in the landscape by the distinctive damage caused to the host plants. Unlike flower thrips, that feed primarily on pollen, chilli thrips feed on various plant tissues. Feeding causes leaf, bud, and fruit bronzing (tissues turn bronze in color). Damaged leaves may curl upward and appear distorted. Infested plants become stunted or dwarfed and leaves may detach from the stem at the petioles in some plant species. Feeding may also cause buds to become brittle and drop. Young leaves, buds and fruits are preferred, although all above ground parts of their host plants may be attacked. Plants with the symptoms described above should be examined closely for the presence of thrips.
Adult Chilli Thrips. Photo: Lance Osborne, Entomology and Nematology Department, University of Florida. Chilli thrips damage causing curling of leaves. Photo: Florida Division of Plant Industry, Florida Department of Agriculture and Consumer Services, Bugwood.org.
Origin and Distribution
Chilli thrips, Scirtothrips dorsalis (Hood), is an important pest of crops in tropical and subtropical regions. An established population of this pest was first detected in the United States on landscape roses in Florida in 2005. In November 2007, chilli thrips were identified on landscape roses in Houston. Chilli thrips have also been detected on a number of ornamental and vegetable plants in retail stores in Northeast and South Texas.
Habitat & Hosts
Chilli thrips have a very broad host range and may feed on more than 150 plant species in 40 plant families. Additional plant species may be added to the list as this pest continues to expand its geographical range. The list includes many commonly grown landscape plant species (Table 1) and many important food and fiber crops. In Florida some of the most common plants attacked in the landscape are roses (Figure 1, 4-5), schefflera, Indian hawthorn (Figure 6), and pittosporum.
Discoloration caused by chili thrips. Texas A&M AgriLife Extension. Discoloration caused by chili thrips. Texas A&M AgriLife Extension. Leaf curl as a result of chilli thrips infestation. Texas A&M AgriLife Extension. Chilli thrips damage. Texas A&M AgriLife Extension
The life cycle of chilli thrips is similar to that of other common thrips species, such as the western flower thrips. Egg to adult development is completed within 12 to 22 days, depending on temperature and host plant species. Females insert their eggs inside plant tissue on or near leaf veins, terminal plant parts and floral structures. Eggs hatch in 6–8 days under optimal conditions, but may take longer at lower temperatures. Immature thrips pass through two larval stages (1st and 2nd instars). The first instar lasts for 2-4 days and the second instar is completed in 3-6 days. During this time larvae actively feed on tender young plant growth, consuming enough food to complete development to the adult stage. Fully-grown larvae molt into a non-feeding, prepupal stage, which may last up to 24 hours, and then pupate on protected plant parts, leaf litter or in the soil near the base of the plant. The pupal stage lasts 2–3 days. In all, chilli thrips may complete their life cycle in 12 to 22 days and females generally deposit 60 to 200 eggs in their lifetime.