Thrips - The Cause of Summer Bud Drop

[nina]

Hi, Charlie,

You keep repeating the reason of bud drop may be the thrips. OK, surely in some conditions, but if the whole greenhouse is blooming like crazy, and only a few varieties drop the buds, and if  the same varieties keep dropping buds from season to season, I think that I can exclude thrips as the reason.
Over the years, I have eliminated those ones that keep dropping buds in summer, I have left only the few ones, that I estimate are worth having in spite of that trait, because they give you the satisfaction in autumn.

I am always amazed to see how hibiscus reacts to very small changes in conditions. This explains, for instance, LL blooms well in your summer, and cannot bloom in mine. Even between me and Denis (Denis is a person who  lives 100 km from me, the same climate zone, almost the same growing conditions) the differences in performace of the same cultivars are surprising. So, the nuances count. Maybe some day I will manage to find out those small nuances and  to improve the performance of some of my cultivars.



ciao, Nina

[Charlie]

Hi Nina, thanks for the feedback. I understand your reasoning, it is very logical. I also use such reasoning to try to understand what I observe with hibiscus.  However, where bud drop is concerned I have learned by my experience to ignore such reasoning and follow my experience. This is because whenever I spray plants that are showing bud drop with thrip effective sprays it is followed by more blooms and less bud drops from those plants.

2 things happen when the temperatures increase. First is that the plants that were adequately watered before now become stressed by the end of the day when the water in the pots becomes low. This has been proven in university studies. The level of stress is not enough to cause gross wilting but it is enough to effect growth and flowering. A second watering is needed on very hot days to prevent this. The other thing that happens is that most insect pests respond to heat with shorter reproduction cycles which results in a huge and rapid increase in the numbers of these insect pests on the plants. This includes thrips, which swarm all over the flowers doing their damage. To combat this, specific pesticides must be used.

Chris has shown us how insects react to flowers in ways that are not visible to humans. Under ultraviolet light some of the cues that insects use can be seen. Likewise I think that some cultivars attract some insects more than others for reasons that are not apparent to us. This could explain why you see some cultivars that drop buds year after year while other cvs do not. My theory is that it is not the tendency to drop buds that differs, but rather the degree to which these cvs attract thrips that differs. It is also possible that there is a different reaction to low water stress as well.

I have always found what I observe in my hot greenhouse to be at odds with the "conventional wisdom" about bud drop. Since it is a commercial greenhouse we probably do more than most hibiscus growers in terms of taking care of the plants. They are frequently sprayed and are watered 2 times or more per day in summer. The greenhouse reaches 40C (well over100F) every day in summer and is as hot as any outdoor climate in American yet we do not have any cessation of flowering during the summer. Why? Well, I think I have explained my theories above. I wish very much I could send you a bottle of Spinosad so you could test this on your own plants but I think it would not pass Customs.

Charlie

[Nievesgirl]

Hi Nina, thanks for the feedback. I understand your reasoning, it is very logical. I also use such reasoning to try to understand what I observe with hibiscus.  However, where bud drop is concerned I have learned by my experience to ignore such reasoning and follow my experience. This is because whenever I spray plants that are showing bud drop with thrip effective sprays it is followed by more blooms and less bud drops from those plants.

2 things happen when the temperatures increase. First is that the plants that were adequately watered before now become stressed by the end of the day when the water in the pots becomes low. This has been proven in university studies. The level of stress is not enough to cause gross wilting but it is enough to effect growth and flowering. A second watering is needed on very hot days to prevent this. The other thing that happens is that most insect pests respond to heat with shorter reproduction cycles which results in a huge and rapid increase in the numbers of these insect pests on the plants. This includes thrips, which swarm all over the flowers doing their damage. To combat this, specific pesticides must be used.
Chris has shown us how insects react to flowers in ways that are not visible to humans. Under ultraviolet light some of the cues that insects use can be seen. Likewise I think that some cultivars attract some insects more than others for reasons that are not apparent to us. This could explain why you see some cultivars that drop buds year after year while other cvs do not. My theory is that it is not the tendency to drop buds that differs, but rather the degree to which these cvs attract thrips that differs. It is also possible that there is a different reaction to low water stress as well.

I have always found what I observe in my hot greenhouse to be at odds with the "conventional wisdom" about bud drop. Since it is a commercial greenhouse we probably do more than most hibiscus growers in terms of taking care of the plants. They are frequently sprayed and are watered 2 times or more per day in summer. The greenhouse reaches 40C (well over100F) every day in summer and is as hot as any outdoor climate in American yet we do not have any cessation of flowering during the summer. Why? Well, I think I have explained my theories above. I wish very much I could send you a bottle of Spinosad so you could test this on your own plants but I think it would not pass Customs.

Charlie

Charlie I think you maybe right ! , I have thrips right now but only on voodoo magic ! I am just now seeing scratch marks on the flowers. I saw in the pest section that voodoo magic is used as an example for thrips.  I need to get the neem oil and spinosad.   All my other cv's are fine. But I will spray them with my bayer tonight to be sure. It says on the bottle it kills thrips but I dpn't think as good as the two products you listed to kille thrips.

[Nievesgirl]

Charlie I think you maybe right ! , I have thrips right now but only on voodoo magic ! I am just now seeing scratch marks on the flowers. I saw in the pest section that voodoo magic is used as an example for thrips.  I need to get the neem oil and spinosad.   All my other cv's are fine. But I will spray them with my bayer tonight to be sure. It says on the bottle it kills thrips but I dpn't think as good as the two products you listed to kille thrips.

forgot to ad I will check other plants once they bloom to see if I seen any scratch marks

[Charlie]

Hi Kerry,

Checking for scratch marks is a good way to see if thrips are around. Some varieties are able to hold onto their buds longer even with thrips than others. Byron Metts, for instance, can be seen teeming with thrips in an open flower but not drop the bud before it opened.

The Bayer sprays don't work well against thrips. They may kill a few but only spinosad, acephate (Orthene) and specialist sprays for commercial growers actually provide adequate control. Spinosad is the best of the bunch and is available to everyone in the US. Some neem products like Safer Bioneem might work but I have not tried them for thrips.

Charlie

[Darkhorse]

I'm pretty sure I have a thrips infestation, as a couple of my plants (5th Dimension and Fiery Furnace) are dropping buds like crazy.  I got some spray at home depot and am hoping the problem resolves once I spray several weeks 2x a week.  At first I thought it was the heat spell, too. 

[Charlie]

The type of spray used is critical for success. Most are not effective against thrips even if they list them as one of the insects they are for.

When we say "thrips" we are actually talking about one species that makes hibiscus buds fall. That one is named "Western Flower Thrips" although it is now found in every state. This one feeds on pollen and lays eggs in buds. There are other thrips which feed on leaves but those are rarely a pest for hibiscus. Some sprays may work on other species of thrips but Western Flower Thrips are more of a problem because they do not feed on leaves and so cannot be killed with systemic pesticides the way aphids and whiteflies are.

Just to repeat - acephate (Orthenex) and spinosad (GreenLight Spinosad) are the pesticides that work against Western Flower Thrips. Spinosad is organic and gentle on beneficial insects, even approved for organically certified food. Acephate is an old style organophosphate pesticide that smells bad and kills many types of insect including beneficials. The only reason I recommend it is because it can be easier for some people to find and it works.

Charlie

[nina]

Hi, Charles,

You have managed to persuade me. Anyway, there is no harm in trying. I think I can find Orthene in Croatia. I will try with it.

Do you know if it is possible to mix Orthene with an acaricide? (we say, to kill two flies with one hit!).

ciao, Nina

[Charlie]

Great - an experiment that will give us some results!  Yes, I almost always mix acephate (Orthene) with whatever else I need to use, such as Avid for mites. The other point of view is that if you only treat for thrips you can spray just the buds and tops of the stems and do not need to spray the entire plant and all leaves top and bottom. This will protect the beneficial insects that are probably living on the plant and protecting it from some other pests.

Spinosad is widely used throughout the world due to its gentle effect on the environment and beneficial insects so you could ask about the availability of it as well.

Charlie

[Darkhorse]

The spray I got is not Orthene, but it contains acephate... it's for roses, so I'm hoping it will work for the hibs too.

[Nievesgirl]

I need to go to home depot today or tomorrow. The thing about Home depot I hate is they never have anything you suggest Charlie lol.  I need to go to an armstrong nursery or just go back to Lakewood long beach area to find what I need ( raised over their) I don't know any good nurseries in LA

[Darkhorse]

I just re-read the label... it's Ortho Rosepride and it is supposed to be effective against Western Flower Thrips... and get this... spider mites (two-spotted) too!!  I really hope so, as I've been fighting spider mites for the past month or two, and I just sprayed this on my plants.  I'm about to lose my Persian Rug to those little...erm... buggers, to put it nicely.

[Charlie]

I'm glad you found this product. I looked it up and found that Ortho Rosepride is a family of care products for roses and other shrubs. The one that seems to closest match what you are describing is the Ortho RosePride Systemic Triple Action Spray. Is that what you have? What I particularly like about this is that it contains acephate which is the active ingredient in Orthene and one of the 2 pesticides that really work against Western Flower Thrips. Since Orthene has become much more difficult to locate this is an excellent find you made! If we can find a distributor we will add it to the HVH store as a thrips solution since we can no longer obtain Orthene through our distributor.

The bad news is that there is nothing in it that will be very effective against mites. Like the Bayer 3-in-1 this one also contains a pyrethroid insecticide that gives fast knockdown of some insects and probably has some effect on mites but won't give good control of mites. The best thing for mites that is available without a permit is horticultural oil sprays made in the evening or in the shade.

Thanks for posting this!

Charlie

[Nievesgirl]

I'm glad you found this product. I looked it up and found that Ortho Rosepride is a family of care products for roses and other shrubs. The one that seems to closest match what you are describing is the Ortho RosePride Systemic Triple Action Spray. Is that what you have? What I particularly like about this is that it contains acephate which is the active ingredient in Orthene and one of the 2 pesticides that really work against Western Flower Thrips. Since Orthene has become much more difficult to locate this is an excellent find you made! If we can find a distributor we will add it to the HVH store as a thrips solution since we can no longer obtain Orthene through our distributor.

The bad news is that there is nothing in it that will be very effective against mites. Like the Bayer 3-in-1 this one also contains a pyrethroid insecticide that gives fast knockdown of some insects and probably has some effect on mites but won't give good control of mites. The best thing for mites that is available without a permit is horticultural oil sprays made in the evening or in the shade.

Thanks for posting this!

Charlie

I am going to have to look for this stuff today thanks for posting that

[Darkhorse]

I have the Ortho Rosepride Insect, Disease, and Mite Control.  I got it at Home Depot.  It's an aerosol spray in a can, and smells like crap.    Active ingredients are acephate, resmethrin, and triforine.  It's supposed to be a systemic spray that lasts for up to 2 weeks.

U guys are welcome.

[Nievesgirl]

Ok I went to OSH instead of home depot ( they never have anything)  OSH had Spinosad  and neem III by green light I bought both. The Spinosad is concentrated so I have to mix it my self ( It smells so badly )  I sprayed all of my plants except 2 of them. I will spray them tonight.