Thrips & spider mites: HELP!!!

figlittle(NCA)September 24, 2009

I live in west Sonoma County, California, and thrips and spider mites are destroying my garden, or what's left of it.

I understand that the drought and dry weather may have exacerbated the problem w/them, and I'm certainly doing my best to conserve what precious water we do have, but I'm now spraying them w/water early morning so leaves dry during the day. Have also tried different insecticides such as Spinosad and now binefrin, but still a problem.

I even resorted to removing each and every rose bud, bagging them in plastic zip bags, and disposing in garbage so don't end up in County compost. This has been absolutely heartbreaking. I'm calling this my summer of the barren garden. There's nothing the thrips have spared! When I examine even the morning glories, I find a tiny hole at the stem-end of the bloom, and sure enough, I also find thrips! I then immediately dispose of those flowers, too, hoping to prevent them from mating and spreading as they are also vectors for other diseases.


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dan_keil_cr Keil(Illinois z5)

We use Orthene in Illinois for thrips

    Bookmark   September 25, 2009 at 7:56PM
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serenasyh(was 5/now Z 8-Kans)

I am truly hoping MichaelG will soon come to the rescue with his advice.

Hugs, Figlittle.

I am too new to roses to have any valuable input. One of the best links I have found is here from the University of Davis, California.

comprehensive in-depth description of thrips management

The link explains that it is very difficult to control thrips even with insecticides because thrips fly away! The link likewise recommends spinosad and insecticidal soap--which you've already tried. Do you also use sticky traps? To me this would really help a lot! against thrips. The only downside with sticky traps is that they might get birds,ladybugs,butterflies or bees. I have read that some forumers have put sticky traps into a small paper cup and covered the opening with larger holed netting (from a fabric store) that had holes just small enough that a larger insect like a ladybug or bee would not be able to enter, but with large enough holes that a thrip could get inside.

Also what we need help from MichaelG is in clarifying whether it is necessary to cut off all your buds and blooms.

The thrips enjoy attacking my roses too, but I am still able to enjoy my blooms. I leave all my leaves unsprayed, hoping they'll feed on that instead of my blooms and as soon as my flowers begin to develop buds (all green, no visible petals yet) I keep hot-peppering the buds during each stage of development. I get very minimal damage from thrips that way. Unfortunately cucumber beetles don't seem to care if there's hot pepper spray, LOL! but the thrips are indeed warded off. It cuts down the damage so that I have anywhere from 75% to 100% protection. However there is a catch. Sometimes I forgo hot-peppering in the autumn because I worry about the bees getting enough nutrients for the fall. The bees enjoy my Lincolns and want to visit and if I hot pepper spray, fewer linger around the roses so I forgo my hot-pepper in September and boy does it make a difference when I don't "hot-pepper", lol!

    Bookmark   September 25, 2009 at 8:20PM
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serenasyh(was 5/now Z 8-Kans)

I would stay away from Orthene. It is not good for humans and has a greater level of toxicity.

orthene has more toxicity for humans

I would go by what the University of Davis recommends instead. I forgot to tell you that the Spinosad that Harold (Phatboyroses) uses is Conserve (also mentioned in the UCD link). He seems very happy with Conserve.

    Bookmark   September 25, 2009 at 8:28PM
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This was discussed here:


This link here is also good but it is much easier to control problems, most of the time, in a greenhouse enviroment:


Growing garlic around the roses according to commercial growers in Holland seems to help a lot.

Here is a recipe for the garlic spray I use, but I do not have thrips:

Garlic Oil Spray Insect Spray

Soak 10-15 cloves of FINELY minced garlic (about 3 oz)
2 tsp. mineral oil ( Monterey NatureÂsOwn Spray Helper = 80% Cottonseed Oil) or Soybean Oil or All Seasons 211 Horticultural Spray Oil - 32 oz at Amazon or Organic JMS Stylet Oil or Fish Oil
600 ml water (1 pint)
1 -2 tsp. liquid dish soap

Soak garlic in mineral oil for 24 (better still 48 hours) hours. Add 600 ml (16oz) water and shake, then strain garlic out with a tea strainer, then add 1 tsp. liquid dish soap. Mix thoroughly. Spray plants with this solution.

Spray only in evening as sun goes down in a light wind.

Test on small portion of one plant to make sure it causes no damage waiting 2-3 days to inspect for damage.

If there is no damage spray plants thoroughly to ensure good coverage. Repeat coverage if it rains.

Pests affected: Aphids, spider mites, thrips, and whiteflies

Note can also kill beneficial: Use sparingly.

Note 2. Addiing very hot FINELY minced chilis seeds an all, about 5 (the very small ones) can help.

Some people use a tobacco remedy but I think that is too dangerous.

Hope this helps

    Bookmark   September 25, 2009 at 11:58PM
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I agree with serenasyh at least from what I have been able to find on the internet.

One last thought if you are not giving your roses enough water, and maybe you are, are you not stressing them? If so your roses then become similar to a wounded battleship making you a vector for enemy opponents. Insects I believe sense who is weak. Just a thought, poorly amended soil may also compound the problem.

    Bookmark   September 26, 2009 at 12:12AM
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This intrigued me so I resorted to my favourite little book covering garden solutions, "The Truth About Organic Gardening" by Jeff Gilman, a really great book if you want to use the least toxic alternative THAT WORKS.

He states Spinosad is great on thrips but from what I read not so effective on mites, it does take a few days to start to become effective.

But Beauvaria Bassiana, a fungus, sold as Naturalis H&G and manufactured by Troy Biosciences (, while slow acting and not able to kill the entire population of mites at one go is nevertheless still very effective. It lasts for three to five days and prefers humid conditions. It is toxic to both thrips and mites and is considered VERY safe (OMRI approved I believe but not positive). So while you may have your work cut out for you it should solve all of your problems over a month or so. It is not very popular, because it is a labor of love to cure the problem but is most probably the most effective, so you might need to call them to find out where you can buy it.

Hot peppers, chemical ingredient - Capsaicin, is a repellant not an insecticide(unless in very high doses), but it will repel for a long time especially mites, whiteflies, aphids and mealybugs.

Hope this helps, by the way I am a newbie to roses and container gardening but not to general gardening.

    Bookmark   September 26, 2009 at 1:03AM
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In Jeff Gilman's new book "The Truth About Garden Recipes", he makes a few points about insect control, stating that garlic is more of a repellant than an insecticide that has medium term effect, say a week or two before you have to respray (unless it rains). The insects themselves will either leave your garden or go migrate to the leaves/buds/flowers you have missed. He strongly recommends that you use insecticidal soap to kill those insects you missed. Hot Chilli preparations either homemade or bought are particularly effective on mites as a repellant more so than an insecticide.

He also likes the contact insecticide ingredient Acephate (not too tough on the beneficials with slight systemic activity), he does not like Imidacloprid for mites only (Bayer uses this in some insecticides) as it has been shown to actually increase the mite population, but could be used once to quickly wipe out an initial problem (some people have written it hurts bees but I have not seen proof of this).

If you area is experiencing a drought it probable that all the gardens in your area are experiencing the same issues so spraying insecticides (a final resort) might only temporarily solve your problem as they will quickly return, maybe via your neighbors; thrips particularly are easily carried in the wind. One treatment might help to at least get it down to a manageable level or continued treatment with Beauvaria Bassiana fungus, if you can find it. If you can please let us know where you got it from.

Thrips love drought especially plants that are drought stricken and thrips feed on mites, a veritable all you can eat buffet for them, mites and plants. One begets the other; similar to the Biblical plagues in Egypt; which in this case may be followed by diseased plants.

In Whitney Crenshaw's "Garden Insects of America" he states that thrips are an important carrier of disease and are hard to remove from flowers and buds, so cutting them off when you initially spray may be a good idea. He further states that plants showing any sign of disease should be immediately destroyed. I am no expert on disease so you should discuss this with others more expert before you pull a plant.

He feels sanitation of course is a key, raking leaves, etc., and that insecticides are a very weak second often being unsuccessful. Perhaps removing your current mulch and replacing it. And above all proper watering is the holy grail of control with this problem; watering washes thrips from plants and seals their pupal stages in the soil, which is why rainfall controls them. If your soil is not holding water well you might want to ask the soil experts what to do, mulch of course helps a lot.

So it seems it might be solvable but will require constant vigilance and a lot of hard work spraying and making up your garlic preparations. One last note, home-made garlic preparations seem to work much better than store bought; you can buy no-skin cloves 3 lbs in a plastic jar from Costco. Store bought chilli concoctions seem to work better than home-made I do not know why.

Hope this helps.

    Bookmark   September 26, 2009 at 6:01PM
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Two other points.

1. Spraying your plants with a strong spray of water or hitting them from AFAR with a power washer will knock a lot of insects off the leaves. In fact doing this on a regular schedule is really helpful.

2. Using Neem Oil in the garlic spray by replacing the other mineral oil with a percentage of the required Neem Oil might help somewhat, so if 2 Tbsp of neem are required for one gallon you would use 2 Tbsp divided by 8 for 16 oz (1 pint).

Note: Make sure that you use the full strength Neem oil (with the Azadirachtin listed as active ingredient), do not use Clarified Hydrophobic Extract of Neem Oil, it is not as strong.

3. Never ever use more than is recommended on the label, it could permanently or temporarily damage, or even kill your plants.

4. Once everything is back to normal use the Garlic and Chilli repellants on an ongoing basis. Insects can build resistance to the same insecticide and possibly even to Neem Oil, although the chemical formulation is more complicated and therfore more difficult for the insect to overcome.

I think I am done on this subject, I think. You might certainly be hoping so.


    Bookmark   September 26, 2009 at 7:09PM
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Found a Beauvaria Bassiana supplier:


Catalog page number 241, now known as Naturalis-L

Not cheap at $65 per quart (32 oz) but 0.30 oz to 1.0 oz covers 1000 sq ft. Application every 3-5 days, for first four treatments, then every 7-10 days should suffice. Minimum four treatments at which point 90% control is acheived. New flies emerging from soil are killed at a rate of 42% to 83%. Even if after 90% are gone and it kills say at 50% you will now by down by 95%, then 97.5%, eventually you may still have some but in such a minute number they will not be noticeable. So long as you water your garden.

Can be pathogenic to bees, so spray in the evening. But Oregon State Extension office states it can be sprayed at anytime as it is not that pathogenic.

Should be used with sticker and as it is primarily a contact spray so good coverage of leaves (upper and lower) and soil coverage is essential.

As it is a contact spray cutting off all flowers and buds for the first four treatments might be a good idea.

Acephate also flair mites so do not use, see article here:

" "

Ortho Rose & Flower Insect Killer RTS containing Bifenthrin is said to be very effective against mites, but at least two treatments are necessary.

Safer Insect Killing Soap is also somewhat effective containing Potassium salts of fatty acids.

Getting stronger Ortho Systemic Insect Killer with Fenbutatin oxide (+ acephate). The Fen stuff kills the mites.

I knew I would be back.

Hope this helps, if it were me I would stick to the safer Naturalis-L, it could even be cheaper in the long run.

    Bookmark   September 26, 2009 at 8:49PM
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See this link for field trials, basically it works but best in humid climate and even better when applied with another insecticide at the same time as it weakens thrips, mites, aphids, white fly, etc, to the point where the other insecticide delivers the knockout blow.

In Spanish and English:

" "


    Bookmark   September 26, 2009 at 9:02PM
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Found this:

Every 5-7 days works best, period.



Finished for sure.

    Bookmark   September 26, 2009 at 9:06PM
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Apologies two posts above link should read:


Also most probably most effective with Ortho Systemic Insect Killer with Fenbutatin oxide (+ acephate)

    Bookmark   September 26, 2009 at 9:44PM
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For spider mites get a few bags of ice and every other day for a 7 days pour one or two bags at the base of the plant. Squirt your leaves off with a strong flow of water every other morning. That is all you need to kill them. Spider mites hate water. Make sure your roses do not dry out, ever. This will surely attract them back.

For thrips go get the new OFF clip on bug replellent and clip it on a strong cane for a couple of nights, or clip it on a stake in the ground next to the bush or you could plant lemon basil at the base of your roses. Or do both.
I hate thrips.

    Bookmark   September 26, 2009 at 10:26PM
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I also garden in Sonoma County, Bennett Valley, surrounded by dozens of acres of unmowed pastureland. Under these conditions, Western Flower Thrips are pretty much uncontrollable unless you want to spray flower buds every 5 days. I don't. I recommend growing more thrips resistant roses, i.e. roses in darker colors, on the outer edges of your garden, on the west side (the side of the prevailing winds). Something in the pigmentation makes the petals more thrips resistant. Many light-colored roses show the browning at the edges that is so annoying. Deeper colored roses can be crawling with thrips and still look presentable.

Also, this high heat doesn't help much. Are your roses well-watered?

For spider mites, nothing works better than the strong spray of water to the underside of the leaves. You have to persistent and not give up after a couple of times. There's even a special hose nozzle for doing this: it makes a strong stream and points up instead of straight ahead. But you don't need that. Keep after them for about 5 days, wait a couple of days, and then go after them again for another 3 to 5 days in a row. You're trying to interrupt their life cycle. Whatever you do, don't spray some general insecticide that will kill all the spider mite predators. I have plenty of roses right now with a branch or two showing tenting of webs from spider mites. I generally look past them and let the predatory bugs take care of them. I don't know who they are, but they are obviously out there because the spider mites never have their way with whole roses, even though it's terribly hot and dry. The water spray works really well. Just take care not to wash the spider mites off onto a neighboring rose. And with our low humidities and high temperatures, don't worry about the foliage drying. It'll dry in a heartbeat. That old chestnut about wet foliage leading to plant disease doesn't really apply to those of us in California in drought conditions unless we're growing really inappropriate, disease-prone roses that will probably have lousy health no matter what you do.

    Bookmark   September 26, 2009 at 11:41PM
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jont1(Midwest 5b/6a)

I know it's not organic, but I use Merit to spray for thrips early in the Spring when the roses are starting their first blooming cycle. I only spray the very top of the bushes trying to get the buds and newly opening flowers. That one time spray in the spring seems to be all that I need to control the thrips. After that I don't have any thrip issues the rest of the year.
I did make the mistake of spraying Merit twice the first year I tried it. I got rid of the thrips allright, but that caused a massive breakout of spider mites that were much worse than the thrips ever hoped to be. I ended up using Kelthane mixed with the Stirrup M pheromone that year and it seemed to do the trick with the spider mites. After that spraying, I then followed up with the underneath water spraying up through the bush to keep the spider mites washed off the rest of the summer.
I spray the Merit later in the afternoon to try and miss the bees as they have bedded down for the day. By morning the Merit spray is dry and seems harmless to the bees.
Now that I have learned not to spray the Merit more than once, I don't have any issues with thrips and spider mites at all the last 4 years.

Good Luck

    Bookmark   September 27, 2009 at 9:43PM
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Oh my! Shame on me that I didn't find all of your generous research and information about how to deal with the thrips and mites. I cannot thank you enough.
I still have thrips & mite infestation. I removed ALL the rose and other infested flower blooms again this season. I could weep. I also discovered both of them on my citrus!
Like berndoodle, I also live near acres of wild grasses, etc., and the wind here is tremendous, especially in the afternoon, early evening.
Yes, as expensive as water & sewer costs are here, I DO keep my roses and other vegetation well irrigated, including spraying foliage, etc. Yesterday I wiped the undersides of citrus foliage w/alcohol-soaked cotton balls. I read that alcohol will kill them on contact, and I didn't harm any bees and killed some adult thrips at the same time. THE BEST KILL I'VE HAD ALL YEAR!
I will try each and every one of your suggestions until I get this under control. Meanwhile while I've been distracted with the thrips & mites, the GOPHERS have been taking huge advantage.
Honolulurose big hugs and extra thanks to you for your generous suggestions.
Now I'm armed and dangerous '-)!

    Bookmark   May 11, 2012 at 2:40PM
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