Get A Grip On Thrips

Several species of thrips are common in Florida, in the landscape as well as in production agriculture.
Flower Thrips – Adult flower thips are yellow with brown splotches and larvae are lemon yellow in color and are wingless. The Florida flower thrips (Frankliniella bispinosa) and western flower thrips (Frankliniella occidentalis) attack hundreds of plant species, including: oaks, roses, citrus, and vegetables.

 

Gladiolus Thrips – Gladiolus thrips (Thrips simplex) are dark brown with a gray band on their folded wings and immatures are pale yellow with red eyes. They are pests of gladiolus and other herbaceous species as well as tomatoes.

 

Chilli Thrips – Chilli thrips (Scirtothrips dorsalis) are pale yellow to grayis-white in color with incomplete dark stripes on the dorsal surface of each abdominal segment. The larvae are off-white. They are pests of various woody ornamentals and annuals including, but not limited to: roses, Indian hawthorn, and plumbago.

Flower Thrips - White or yellow flowers with open structures allowing easy accessibility to the stamens and pistils are preferred. Feeding and damage on buds, flowers, and leaves results in discoloration and premature dropping. Adult western flower thrips are vectors of tomato spotted wilt virus (TSWV), a common virus in tomatoes, peppers, and potatoes. In tomatoes, the virus causes small dark brown spots to appear on young leaves, stems, and leaf petioles eventually causing plants to exhibit one-sided growth. Immature fruit of infected plants will display mottled, light green rings with raised centers and mature fruit will display unique orange and red discoloration. Female flower thrips lay their eggs in the ovaries of blueberry flowers and the emerging larvae leave scars on the ovaries. The damaged is magnified when the ovaries develop into fruits.

 

Gladiolus Thrips - Gladiolus thrips may be seen on foliage on overcast days, but hide in flower buds and beneath leaves in sunny conditions. They discolor flowers and foliage and cause corms (bulbs) to become soft and prone to decay. Flowers with severe damage fail to open.

 

Chilli Thrips - Chilli thrips attack all above ground plant parts, preferring the young leaves, buds, and fruits. Tender leaves, buds, and fruits turn bronze to black in color from heavy feeding. The damaged leaves curl upward, appearing distorted. Chilli thrips cause stunting or dwarfing on infested plants as well as defoliation in some plants. They prefer the dry season and numbers are suppressed during the rainy season.

Fruit and Vegetable Production – A few flowers should periodically be sampled by placing them in small containers with 70% alcohol (flowers can also be shaken on white paper). The container can then be shaken to eject the thrips which can then be examined under a microscope with at least 40X magnification to determine the species (your county agent can help with this process). Counting the thrips from 20 flowers per acre should be sufficient to estimate population density. Several small, medium, and large fruits should be examined directly per acre. It is important to examine small, developing fruits frequently because eggs are generally laid during the flower stage, and larvae on small fruits is the first indication of a problem.

 

Sticky Traps – White sticky traps are preferred (over yellow and blue traps) for thrips collection as yellow traps attract a large percentage of beneficial insects and it is difficult to see thrips against a blue background. Traps should be placed 1 -2 feet below the tops of plants at a rate of at least four traps per acre. Traps should be monitored and changed weekly.

 

Ornamentals – It is important to check plants with abnormal growth for chilli thrips populations. The underside surfaces of leaves become shiny at the beginning stages of infestation. The leaves then become discolored and curly. Five to 20 leaves should be collected, from plants showing symptoms, and placed in a zip top bag to prevent adults from escaping. Label the bag with the location information, host plant, date collected, and name of the collector and bring to your local Extension office or send next-day delivery to an expert.

A well thought out integrated pest management program is the most effective way to manage thrips. This includes the incorporation of biological controls, cultural practices, and reduced-risk insecticides.

 

Biological Control – Several arthropod species help keep thrips population in check including: green lacewing larvae, big-eyed bugs, minute pirate bugs, damsel bugs, insidious plant bugs (Orius insidiosus), ladybird beetles, parasitic wasps, predaceous thrips, and predatory mites. Verticillium lecanii, a fungal pathogen, may also be purchased and applied to reduce thrips populations. Insect-parasitic nematodes in the genus Thripinema have been found to parasitize some thrips species.

 

Cultural Control – As previously mentioned, sticky traps can effectively monitor thrips populations. In vegetable production, ultraviolet reflective mulch helps repel migrating adults of western flower thrips. It is advised to limit the use of broad-spectrum insecticides that may suppress beneficial insect populations. Over-fertilization above recommended rates of nitrogen may result in increased preference and performance of thrips.

 

Chemical Control Of Thrips In Blueberries – A new reduced-risk insecticide for thrips control in blueberries is Delegate WG (spinetoram, Dow AgroSciences). This insecticide is reported to have good residual activity for thrips control. The labeled rate for Delegate WG is 3 to 6 oz. per acre. The post harvest interval (PHI) is 3 days and the re-entry interval (REI) is 4 hours. It should be applied in the morning or late in the evening so it will dry before bees become active.

 

Chemical Control Of Chilli Thrips – Below are suggested insecticides for chilli thrips control.

 ¹Use restricted to greenhouses

 

 

 

G = greenhouse I = interiorscape L = landscape N = nursery S = shadehouse  

Federal and Florida laws require that all pesticides must be handled and applied in strict compliance with the label and worker protections standards. For complete information pertaining to use of any insecticide, follow the label. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture or the University of Florida.