Thrips – By Mark Govan, Host “Florida Gardening”

No matter what type of landscape plant you are growing, there is a pest that you need to be aware of, thrips. Thrips are very small insects with rasping sucking mouthparts which damage plants by tearing the leaf or flower surface with their mouthparts then sucking the plant juices which seep out. This feeding causes some of our plants to drop their flower buds and in many cases cause the leaves to be deformed. Insecticides currently available can keep some of these thrips in check but there is a new hybrid we need to talk about. This hybrid thrip is damaging Florida Landscapes at an outstanding rate and the insecticides we are familiar with using are no longer effective in controlling this pest. This new thrip is called the Chili Thrip. Today we will discuss how this pest came to Florida, the plants on which it feeds, the damage they cause, and how to properly identify and control the Chili Thrip.

            Chili Thrips (photo above from IFAS.edu) arrived in Florida on plant material or fruits which enter the State on a daily basis. First signs of this new pest were detected in 2004 and have quickly distributed themselves throughout the southern states. Although they are very small (2mm or .08in) in size, the damage to your plants can be severe. These pests have now been found on over one hundred plant species including vegetables, fruit trees, and ornamental crops. Even though they are similar in looks to the common thrips many of us have had to deal with them on our ornamental plants. This thrip is so small that the only ways to determine you have this pest is either through the use of a microscope or with the ability to properly identify the damage caused by these pests. I recommend if you think you have Chili Thrips you should call in a professional pest control applicator to inspect your plants. If they are found they can do an application of an insecticide to control them.

            Damage to plants with this pest can be found on any above ground surface. As this pest feeds, distortions in the leaves or flowers begin to appear. The first symptom you may notice on your landscape plants is the abnormal new growth on the top of the plant. This growth may look similar to aphid damage at first but there will be no sign of an insect you can see on the plant. As leaves begin to curl on your plants you will notice most of the new growth to be very small and distorted. Remember, with over one hundred common landscape plants being attacked by this pest you will need to perform weekly walk-troughs’ of  your garden or landscape. Watch for these symptoms and when noticed follow the identification and control section listed below.   

            Roses are particularly susceptible to this pest. I have seen rose bushes of the variety “Knock Out” completely killed by this pest. You may even notice a color deviation or black streaks on the leaves of the plant. Instead of an entire new rose leaf being the dark red or green, the color seems to be spotted or mottled. If your rose has produced a new flower bud you may notice these buds are smaller and when they open you will notice the edges of the rose petals will looked burnt. Some blossoms will also show a distortion in color and in size.

            When I first started to see this type of damage on my plants, I scoured the plant looking for aphids or scales. Even when I used a hand lens I still did not find any pest. I was even told it may be a fungal problem. Not until I took the leaves and placed them under a microscope did I see that indeed there were Chili Thrips. This is why it is so important for you to be able to recognize the damage caused by these insects. Taking samples of suspected damage to your local county extension office for identification may help you to identify these insects early to limit the damage to your plants then you can initiate control measures (Photos by Jim Small – ARS Consulting Rosarian).

            Control measures need to be taken early if an infestation is found. When pest control operators first started treating for this pest the main control product was bifenthrin (Talstar). Unfortunately, the discovery that Chili Thrips were resistant to bifenthrin was not identified for about a year resulting in the loss of many plants. If you have been using this product as your main line of defense against insects, you need to change products periodically to lessen the chance insects on your property will build up a resistance.          There are several new products which have been tested and are known to work much better. These products are broken into two classes. Systemic, meaning the product is taken up by the plant and distributed throughout the plant internally (not good for vegetable crops) and non-systemic (good for vegetable crops). If I am treating a vegetable crop for Chili Thrips, I recommend spraying the foliage with spinosad (Conserve). Spinosad is made from certain soil microbes and can be used freely on most vegetable and fruit crops. This organic product gives you the ability to control thrips, cut worms, aphids, and other insects. Applications will need to be repeated but be sure to mix fresh product each time you apply. Please allow at least thirty days between applications.

            For you landscape ornamentals I prefer the systemic products such as acephate (Orthene), clothianidin + bifenthrin (Aloft SC), or dinotefuran (Safari). All of these products are locally systemic meaning they will be taken up by the plant and distributed to the new growth. Applications to the leaf surface and soaking the root system seem to offer the best control. These products may be difficult to find at your local nursery but can be ordered or applied by a local pest control applicator. Be sure to read the entire label on each of these products before using in your yard or garden.

            Chili Thrips can be a devastating pest in our landscape or gardens. I hope the photos and the descriptions I have outlined above will help you to identify these pests around your home. By using the products I have outlined above you should be able keep your plants healthy and green. Keep active in the garden and remember, without plants we would not be here. 

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