Karny Thrips, A New Invasive Pest

Posted Jun 25, 2024, in ,

Originally from Southeast Asia, Thrips parvispinus, often called Karny thrips, has spread to different parts of the world, including North America. It’s believed that they first came to the United States in Hawaii in the early 2000s. Then, it was found in Florida in 2020 and later in Georgia around 2022 or 2023. New sightings in the USA include Colorado, North Carolina, and South Carolina. In Canada, it was spotted in Ontario in 2021 or 2022. This fast expansion shows how tough it can be to deal with this invasive bug and emphasizes the importance of keeping an eye on it and finding ways to control it to protect crops and plants. Plus, it’s worth noting that methods used to manage other thrips pests don’t always work against Thrips parvispinus.


Figure 1.Thrips parvispinusadults. (Left) female, (Right) male. Reference:Thrips parvispinuson www.thrips-id.com

Host plants

Thrips parvispinuscan feed a wide variety of host plants, ranging from ornamental plants to vegetables and fruit crops. They feed on plant tissues by piercing the cells and extracting their contents, causing severe damage, wilting, and, ultimately, yield loss. While the comprehensive list of their hosts in North America is still under assessment, their known host species list includes gardenia, hibiscus, pinwheel jasmine, mandevilla, anthurium, hoya, dahlia, chrysanthemum (mums), ruellia, schefflera, citrus, strawberry, eggplant, peppers, cucumber, beans, zucchini, and more.

Damage

Adults and young Karny thrips munch on leaves and flowers, which can really mess up plants. Spotting the damage early is key to handling these pests well. So far, there’s no evidence that they spread any viruses. Signs that your plants might be infested include silver marks on leaves (especially big ones), weird-looking or stunted growth, leaves falling off too soon, scars on fruits, and seeing the bugs themselves. It’s important to correctly ID them because their damage looks a lot like damage from other bugs, like broad mites. To be sure it’s Thrips parvispinus causing the trouble, gently tap an infested plant over a white piece of paper to shake off the bugs, which makes them easier to see and identify.


Figure 2. Pepper leaf showing scars caused byThrips parvispinusfeeding. Photo: L.S. Osborne, UF/IFAS-MREC.


Figure 3. (Left) Pepper fruit with scarring. (Right) Pepper plant with damage caused byThrips parvispinusfeeding. Photo: Ana Meszaros, UF-IFAS Palm Beach County.


Figure 4. Terminal stems of Gardenia showingThrips parvispinusdamage. Photos: Left: Ana Meszaros, UF-IFAS Palm Beach County; Right: Lyle Buss, University of Florida.

Description

Karny thrips are super tiny, only about 1 mm long, so it’s hard to see them without a magnifying glass or someone who knows what to look for. Grown-up female thrips are usually dark brown, sometimes black, with light legs and head. Their wings are lighter near the base. On the other hand, male thrips are all yellow and about 0.6 mm long. When they’re babies, they look a lot like the grown-ups but without wings. Their life cycle includes eggs, two baby stages, a prepupa stage, a pupa stage, and then they become adults, all happening in about 13 to 14 days. Males don’t live very long, only about six days, while females last for about nine days. The female thrips can reproduce without even finding a partner and can lay around 15 eggs during their lifetime.


Figure 5. Adult femaleThrips parvispinuson pepper (right) and squash flowers (left). Photo: Ana Meszaros, UF-IFAS Palm Beach County.


Figure 6.Thrips parvispinuslife cycle. Reference:Thrips parvispinuson mrec.ifas.ufl.edu/

Monitoring

Karny thrips go through their life cycle pretty quickly, so it’s important to check on your plants every week. You can do this by tapping them gently over a white sheet of paper to see if any thrips fall out. Another good way to keep an eye out for them is by using yellow sticky traps. Checking regularly helps you catch them early and deal with them before they become a big problem.

Management

To handle Karny thrips, you’ve got a few options: cultural, biological, and chemical control. To start, keep your plants clean and tidy, and get rid of any infested plants right away. Checking on your plants regularly is key, especially when there aren’t many pests around. If you do spot some, you can use natural enemies like predatory mites, green lacewings, minute pirate bugs, and nematodes to help keep them in check. These guys target different stages of Thrips parvispinus and are a sustainable way to deal with the problem. If things get really bad, you can use insecticides made to control thrips, but make sure you switch between different kinds to stop the bugs from getting resistant. Always follow the instructions on the insecticide label and wear the right gear when you’re using it. Weekly treatments seem to provide the best control in the residential landscape. By using a mix of these methods, you’ve got the best shot at keeping Karny thrips under control.

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