THE NEW BUG MAN: Watch Out For Thrips parvispinus In San Diego County
- k-england
- Feb 28
- 3 min read
By Eric Middleton PhD, IPM Advisor, University of California Statewide IPM Program and Cooperative Extension, San Diego, Orange, and Los Angeles Counties, for Let’s Talk Plants! March 2025.
Watch Out For Thrips parvispinus in San Diego County
San Diego is a hub for nursery and floriculture production in the United States, with a mild climate that allows many kinds of plants and flowers to grow. Unfortunately, this also makes the area vulnerable to a wide range of invasive pest species, among them, Thrips parvispinus. Thrips parvispinus is a small thrips species that feeds on numerous ornamentals and even food crops. Their main hosts include Dipladenias, Mandevillas, Gardenias, Anthuriums, and peppers of all kinds. Adults and larvae feed on flowers and young leaves causing distortions, scarring, and sometimes even killing the plant. This damage combined with a rapid generation time makes T. parvipinus a serious pest of ornamentals and peppers.
While Thrips parvispinus was not known to be present in California, T. parvispinus can arrive undetected and become established before growers are aware of the threat. With this in mind, I hired two students to help me visit commercial garden centers around San Diego County and check known host plants to see if T. parvispinus had entered California undetected. Unfortunately at the very first garden center we visited, we found T. parvispinus present on multiple host plants. We continued our survey through December 2024 and ended up finding T. parvispinus at almost every store we visited throughout San Diego County, and even up into Orange County. They were found feeding on Dipladenias, Mandevillas, Gardenias, and peppers.
Working with the Pest Exclusion team at San Diego County Ag Weights and Measures, we identified a single grower who almost all the plants were coming from. The plants were placed on hold, several thousand were destroyed both at the growers’ operation and at garden centers, and the sale of host plants from the grower was temporarily blocked. After all of this, we surveyed the garden centers again, and while we did see plants that showed signs of T. parvispinus feeding, we have not yet found any new T. parvispinus the second time around. Additionally, working with the UC Master Gardeners from San Diego to Santa Barbara, we checked host plants out in the landscape and so far, have found no T. parvispinus outside of commercial garden centers. However, there is still a good chance T. parvispinus has already become established in Southern California judging by the scale and spread of infested plants in garden centers. While we continue to look for it, growers, landscape managers, and residents should also keep an eye out for T. parvispinus and recognize the damage it causes on common hosts. After T. parvispinus feeding, Dipladenias and Mandevillas will develop notched leaves, have stunted growing terminals, and show signs of scarring on leaves and flowers. Gardenias will have scarred and stunted new leaves with some distortions. Pepper leaves will become distorted and will take on a crinkled appearance with some scarring also visible.
While it will be difficult to positively ID T. parvispinus on your own, watch for small, dark, and active thrips. Adult female T. parvispinus are smaller and darker than adult females of common species like Western Flower Thrips. If you see one under magnification, adult female T. parvispinus have a brownish head and thorax with a dark abdomen and wings that appear light close to the body and darker further out. Keep an eye out for this damaging invasive thrips species and reach out to me or another UC Cooperative Extension advisor if you have questions or think you have found it!
Comments