Chilli Thrips (Scirtothrips dorsalis)
Have Now Arrived in Southern California

By Kitty Belendez, Master Rosarian
Santa Clarita, California

October 26, 2015 -- I've recently had many questions about the chilli thrips insects (Scirtothrips dorsalis) and how to control them. Since chilli thrips are a new insect to California and were only identified this fall, I really do not yet have much experience with their control. Chilli thrips are now all over Southern California in public gardens as well as private gardens. I first recognized them in my garden this past August after being alerted by a friend, so I am just now beginning to try the control methods that were recommended to me by the experts and friends in Florida that have been dealing with the chilli thrips for about 10 years. I have done some Googling on the issue, and have talked to people with more experience. The website at the University of Florida has some valuable information and photos. See link below.

I want to clarify that the methods I use are not for everyone. I grow about 300 roses so my spray machine holds 14 gallons of spray mixture. I buy very concentrated chemicals because it is more cost effective for my large garden. I do not recommend concentrated chemicals to the home gardener with a one- or two-gallon spray tank. There are many other less concentrated products that are more appropriate for use in a small garden. You will need to do some research on the available products for your particular needs.

THIS IS WHAT I AM DOING TO CONTROL CHILLI THRIPS IN MY PERSONAL GARDEN:

For chilli thrips, I rotate weekly the insecticides Merit or Conserve, which are VERY CONCENTRATED products for people with large sprayers and large gardens. These concentrated products are expensive and available from www.rosemania.com.

The main ingredient in the brand name Merit is IMIDACLOPRID
(Contact and stomach poison systemic. Good root systemic activity. Shorter systemic activity when foliar applied.)

The main ingredient in the brand name Conserve is SPINOSAD
(Translaminar. Stomach poison. Not absorbed from the soil. Quick knock-down.)

You should be looking for the ingredient names (imidacloprid OR spinosad) on the product labels. There are plenty of products already on the nursery shelves with those ingredients in them. Although other products are probably not as concentrated so you would need to use the correct amount according to the instructions on the product label.

For my 14-gallon sprayer, I use only 1.5 teaspoons of Merit (wettable powder) in 14 gallons of water.

ROTATED WEEKLY WITH:

For my 14-gallon sprayer, I use only 2 tablespoons of Conserve (liquid/shake well) in 14 gallons of water.

I DO NOT mix these two products together. Rather, I rotate them once a week. I spray my roses with Conserve one week, and Merit the following week. I do however, mix a fungicide with either Conserve OR Merit, as well as a spreader-sticker such as Indicate-5 when I spray. My fungicide of choice is Compass (extremely expensive!) rotated weekly with BannerMaxx. But again, these fungicides are concentrated for large gardens with large spray machines, so you need to read the product labels of whatever fungicide or insecticide you choose. 

If your sprayer is small, like 1- or 2-gallon, then it might be difficult to measure the correct amount of concentrated products for a small sprayer. I emphasize that you MUST READ THE PACKAGE LABELS AND FOLLOW THE PROCEDURES AS INSTRUCTED for whatever product you choose to use.

I can so far report that after 4 weeks of weekly spraying, Merit (imidacloprid) rotated weekly with Conserve (spinosad) appears to be very successful in controlling chilli thrips in my garden. At least for this fall's blooming season. I take care to wear a respirator face mask, nitrile gloves, boots, eye goggles, and hat, THEN spray each bush entirely, not just selected canes. Partially spraying a bush will NOT control chilli thrips. Cutting stems off and not spraying at all will NOT control chilli thrips. The chilli thrips love the new foliage as well as the blooms so once they appear, the foliage, stem, and bloom will look distorted, stunted, with the telltale brown streaks on the undersides of the new foliage. You probably won't even see the chilli thrips because they are too tiny to see with the naked eye. So you need to identify them by the damage they do. See photo above.

See the link to the University of Florida for other products they recommend for chilli thrips. Orthene, Tristar, Safari, and Avid are also on their recommendation list. I periodically use Avid for spider mites, and Orthene for scale insect and green bud worms. So I'm occasionally using those products anyway. Using Orthene too often kills good bugs, so it could increase your spider mite population.

I want to emphasize that I am NOT an expert on chilli thrips. They are new to me after growing roses for 30 years. I am still learning. 

Here is a link to University of Florida with lots of info, photos, and more links to info on Chilli Thrips.

Here is a link to basic info and suggested chemicals to control chilli thrips at University of Florida.

Here is a link to University of Florida with LOTS of info, photos, and more chilli thrips links.

© Copyright Kitty Belendez. All rights reserved.

Photos © Copyright by Kitty Belendez

For questions about Santa Clarita Valley Rose Society, contact:  Kitty Belendez

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Updated January 3, 2016

Chilli Thrips Damage on a stem of 'Golden Holstein' rose.