If you spray buds that are open enough to wiggle into, you will be killing pollinators. It is very difficult to control thrips in an environmentally responsible way. For this reason, most gardeners just put up with them and discard varieties that chronically show severe damage. In my own garden, thrips are normally a noticeable problem only for a small part of the growing season, usually the latter part of the first flush. I stopped trying to control them long ago. In other climates or gardens, they are a larger problem.

Many rose exhibitors spray buds every day or so during the runup to a show. Occasional application does little good because the thrips fly to the flowers from reproductive host plants, which are very numerous and widespread. The best chemical to use is spinosad, which is not too hard on thrips predators, but can kill bees if it is still wet or if it contaminates pollen.

Immature thrips may be feeding on rose foliage (as well as many other reproductive hosts), but most people don't spray the whole plant.

I've no grasp whatsoever of what rose-growing in your section of California entails. Gotta say, though, that I'm VERY surprised/disappointed/dismayed that none of your fellow Californians has responded to your post after all this time. They're usually quite vocal/opinionated/knowledgeable. Surely one of them will weigh-in soon . . .

When do thrips appear in your garden each year? How long do they remain after their first appearance? Do folks out there actually spray to control them? If so, what insecticide do they prefer for thrips eradication? How often do they use it? Is it really effective?

Jaxondel, it seems that they have been here for a few weeks, and that seems pretty typical. I think in the past they have remained for awhile (4-6wks?). Like Michaelg said,
"thrips fly to the flowers from reproductive host plants, which are very numerous and widespread", so it really is a pain in the backside!!They are on lots of flowers in my yard but the harm it does to my roses is the worst.
I don't like using anything that harms good guys, especially bees since I have quite a few in my garden.
I have not tried spraying anything yet and probably won't, but still am very curious about what other Californians are using. I'm also surprised that nobody else has responded.
Janet

This is the worst year i can remember for thrips here in CT. Usually we get them in July and into August when I pretty much ignore everything because it is just too much to try to keep things up during the summer heat. This year the flush was way early and so were the thrips and now with all the recent rain we have a huge second flush that is being ruined by thrips. There is really nothing you can do for the whites and pinks that thrips like. Spraying will not stop them and you will kill all your bees so don't do it. They will be gone soon and the late summer-fall flush will be incredible.

Hello! I live in the San Fernando Valley and last year invested in a bottle of Conserve SC. It is a great product and works on quite a few pests. Thankfully the bottle will last a long time, cause it is a bit pricey. It is highly toxic to bees, so I wait until the evening and double check to make sure there are no bees still active in the garden. But, even doing that I am sure there have been some bee deaths here and there. Conserve's chemical name is Spinosad and it seems to be one of the least offensive pesticides you can get. It is certified to use on organic crops. It has very low beneficial impact, and I have lots of green lacewings, lady bugs, and praying mantis in my garden, so I know they are okay with it. It seems that if you are going to spray anything at all you have a good chance of killing something that you don't want to. Things like neem oil, canola oil, or even Dawn, while easy on people and pets, will kill beneficials- whereas Spinosad is very selective on what it affects. So, if you are going to spray something you have to make a judgement call on the possible side effects to other plants and beings in the yard. No pesticide is perfect, but for me and for lots of other people, Spinosad is the way to go. I will say that you must keep up the spraying to keep the thrips away consistently, something which I am not very good at! Haha! The label says to alternate with another chemical too, but I usually just take a couple weeks off so the thrips don't establish resistance to it. Lots of googling and surfing the forums will answer most questions you may have. Also, Spinosad is very effective on caterpillars, and even has some miticidal activity when combined with a non-ionic spray adjuvant. I use Dyne-amic. The use of Stirrup M may make it even more effective against Mites.

In looking at your original post-
-I spray the entire plant, tops and bottoms of the leaves. The soil gets lots of drippage from the plant.
-I try to do it when there are no open blooms, but as long as it is not too hot, and not forecast to be for a day or two, I will spray with open blooms. I won't spray if it's supposed to be 85 or hotter.
-I find that thrips are in the garden year-round, as soon as the plants start blooming, and that they are in almost every bloom on every plant. I have Peacock Gladioulus and Stargazer Lilies that I know the thrips like. They seem to be attracted to lighter colored blooms, especially white. My Fair Bianca is the one that gets them the worst.
-I wear long pants, long sleeves, Nitrile gloves, and a dust mask with charcoal lining, to keep the smell of the Conserve away. The mask is not listed as being required for spraying Conserve, but I find the smell of Conserve for some reason makes my sinuses burn the next day. The charcoal lined dust mask completely takes it away. I believe it was packaged as like a painting dust mask or something. Sort of gray colored.
-Another thought- Spinosad is made in pill form to give to dogs for month-long flea control. Puts the mind at ease about having our dog in the backyard after spraying, also about being out in it myself. The flea product is called Comfortis.

I, too, use conserve and really like it. I just mist the tops of my plants about once or twice a week before show season when they are still green buds. I use about 1.5 gallons on 250 plants. This works really well for thrips. I also have used Comfortis for my Chihuahua's fleas. Really great for that. A vet friend told me it makes some dogs sick, so be careful.
Any of you Conserve advocates want to take a shot at the thread "What may happen in British Columbia about spraying" above this thread?

I had nothing but a sore back for my efforts spraying for Western Flower Thrips. The big problem for someone with a lot of roses is the life cycle.

Quoting from University of Minnesota, emphasis added:
"Depending on environmental conditions and nutrient levels, female WFT lay 130Â230 eggs during their lifetime (Robb 1989). The female WFT has an external ovipositor with two opposable serrated blades that are used to cut through the plant epidermis and deposit eggs in the tissues below (Childers and Achor 1995). Eggs are deposited in leaves, bracts, and petals and hatch in 2 to 4 days (Pfleger et al. 1995). The eggs of WFT are fairly well protected and few pesticide sprays are effective against them.

"WFT do not overwinter outdoors in the Upper Midwest but overwinter in soil and clover in the Mid-Atlantic states and southern Pennsylvania (Felland et al. 1995). Under greenhouse conditions, WFT probably reproduce continuously throughout the year.

"WFT give birth to large numbers of young, have rapid reproductive cycles, and increase their population faster than their predators, so early detection and control is essential (Mound and Teulon 1995). The life cycle of WFT consists of five stages: egg, two feeding larval instars, nonfeeding prepupa and pupa instars, and adult (Figure 1). The development time from egg to adult is 7 to 13 days when temperatures range from 62 to 98F (Robb 1989)."

Spinosad works upon contact or feeding on sprayed material. Given the extent of thrips in some environments (like mine), it's can be really tough to get the material on the bugs. I've learned that white roses grown close to the wilder areas of my garden are going to suffer, while darker roses in the same location, filled with thrips, look just fine.

Here is a link that might be useful: Western Flower Thrips In Greenhouses