Corporation) for his feedback regarding the industry perspective on managing WFT. The bulk release formulation is more effective than sachets, however, some growers found that sachet packets provide more protection to the the mites. Eggs hatch into first instar nymphs that eventually transform into second instar nymphs. TSWV is a problem mostly on vegetable plants such as tomatoes and peppers, while INSV is the predominant tospovirus found in ornamentals. Use a blue non-sticky card to attract thrips to indicator plants since WFT are more strongly attracted to blue than to other colors. Applications conducted after flowers open are, in general, too late since damage has already occurred. Labor will be saved if this is done when baskets are being hung. Overlapping generations of thrips within a greenhouse may result in continuous virus transmission. They reported that Lemon Gem marigold would not be acceptable as banker plants because very few of the Orius nymphs reared on this marigold developed into adults. Flowers and plant tips can be shaken over a piece of paper for additional monitoring. Life Cycle drawing credit: See references - Sanderson J.P. 1990. Females typically lay eggs underneath the epidermal layer of the leaf surface, which protects them from exposure to contact pest control materials and biological control agents such as predators and beneficial nematodes. The key to WFT management with pest control materials is to initiate applications when populations are “low,” which avoids having to deal with Depending on environmental conditions and nutrient levels, WFT females lay 150-300 eggs during their lifetime. Visual inspections can be improved by blowing lightly into the blossoms or growing points. A successful WFT management program does not require “eradication” of the pest, but instead maintaining WFT populations at levels such that no “major” damage is noticeable. It is difficult to diagnose tospovirus infections of greenhouse plants using visual symptoms alone. It should be the goal of all greenhouse producers worldwide to develop WFT management programs that preserve the longevity and effectiveness of currently available products. Get one year of Greenhouse Product News in both print and digital editions for free. Flower-feeding thrips are routinely attracted to bright floral colors, especially white, blue, and yellow, and will land and attempt to feed. By stimulating feeding, the thrips had more contact with infected spores on treated leafs, resulting in better control. In addition to direct feeding injury, WFT vector two tospoviruses, the impatiens necrotic spot virus (INSV) and the tomato spotted wilt virus (TSWV), both of which can be identified using on-site test kits. Organic sprays, such as natural pyrethrum (e.g. The IPM Practioner 17(4) pp 1-11. WFT is the most prevalent species of thrips in Massachusetts greenhouses. Once thrips acquire INSV or TSWV, virus multiplies within the salivary glands and other tissues of the thrips and is later transmitted to new plants by the feeding of the infected thrips after it has reached the adult stage. It is difficult to manage WFT in greenhouses for a number of reasons, including its ability to feed on a broad range of plant types, high female reproductive capacity, rapid lifecycle (egg to adult), small size (_ 2.0 mm long), feeding habit, cryptic habitats (e.g., unopened flower buds) and resistance to pest control materials. Larvae rese… Monitoring and Controlling Western Flower Thrips. As with many greenhouse pests, WFTs have a fairly short time from one generation to the next so they quickly will build up tolerance to pesticides. When thrips are present on the lettuce crop, insecticides are often the only viable control alternative. Using On-Site Test Kits to Detect Tospoviruses On-site test kits can be used to determine whether or not tospoviruses are present in greenhouse plants. The mode of action and activity type (contact, translaminar, systemic, and stomach poison) of the pest control materials registered for use against WFT are presented in Table 1. For example, avocado thrips and greenhouse thrips superficially scar avocado fruit skin. However, the virus is systemic in fava bean plants and once infected, plants should be discarded immediately so as to not serve as a source of infection. If there is a very big thrips problem in your area, some plants have resistant varieties. Lyon, S., R.G. Tospovirus symptoms often mimic symptoms caused by other problems such as nutrient deficiencies. One problem with testing for viruses is that some host plant species do not express TSWV or INSV symptoms until long after the initial infection. This is why WFT are typically present in secluded habitats on plants, which again protects them from exposure to contact insecticides and biological control agents. Since the tolerance for WFT damage on most greenhouse-grown crops is relatively “low,” the principal management strategy used to deal with WFT populations involves the use of pest control materials. Symptoms vary depending on plant species, cultivar, developmental stage of the plant, and environmental conditions. L.B. The life cycle consists of an egg stage, two nymphal stages, two pupal stages and an adult. Be sure to contact your local or regional extension entomologist if you have questions or require assistance regarding management of WFT. In Massachusetts greenhouses, WFT can be found year-round whenever temperatures are favorable for their development and plants, including weeds are available for food. Adults however, do not transmit the virus to their young and there is no transmission from adult to egg. Biological control of western flower thrips, Frankliniella occidentalis with Orius species in eggplant greenhouses in Turkey 470 Although the thrips number per leaf in 6 O. laevigatus-released plots was statistically different from the other plots after 7th of April, it was above the economical threshold (p<0.05) (Table 1). However, the bad ones need to be controlled and there are some specific ways to go about controlling thrips. The vigour of the plant is reduced by loss of chlorophyll. They are used in biocontrol programs when the weather warms in spring and beyond, in addition to other biocontrol agents already being used. All rights reserved. However, if INSV or TSWV is present, the tolerance levels for thrips is zero and a strict thrips control program should be implemented. Try not to overfertilize plants, as this can lead to more thrips damage. MOA group numbers are found on many pesticide labels and are listed below for selected materials listed for managing WFT. Monitor for thrips as soon as plants or cuttings are received. Early in the cropping cycle, and when plants are primarily in the vegetable stage, try to avoid using the “big guns” or those pest control materials with specific modes of action. Pest control materials with contact or translaminar properties are often used to regulate WFT populations whereas systemic pest control materials when applied as a drench or granules to the growing medium typically do not translocate into flower portions (e.g., petals and sepals) at sufficient concentrations to impact WFT adults that normally feed on flowers. Each MoA group is assigned an Insecticide Resistance Action Committee Group number (IRAC code). The use of yellow sticky traps will help to detect emerging adults. Treatments should stop when numbers of thrips have declined to an acceptable level. Sprays applied to control thrips disrupt biological control of other pests such as twospotted spider mites, lygus bugs, whiteflies, and other insects. Bug Clear Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer), fatty acids (e.g. An adult female can live 2-5 weeks (sometimes more, depending on temperatures) and will lay 40-100 eggs on the plants in their lifetimes. However, it is important to note that any WFT Read on for some practical and effective suggestions to manage these destructive pests. R. Chris Williamson, Turf and Ornamental Specialist Revised: 4/25/2004 Item number: XHT1022 . Pear thrips (Taeniothrips inconsequens) Western flower thrips (Frankliniella occidentalis) . Discard tomato spotted wilt virus infected plants. The only way to maintain WFT populations at “low” levels are by timing of applications and thorough coverage of all plant parts. Amblyseius cucumeris adults prefer to feed on 1st instar larvae and are unable to kill adult thrips, so early detection and a sound sampling plan is part of effective control. Western flower thrips (WFT) Frankliniella occidentalis continues to be a serious pest of floriculture crops in New England. Thrips can also be collected from sticky traps and tested using the test kits. Lyon S. 2002. Furthermore, consider releasing biological control agents such as Neoseilus (=Amblyseius) cucumeris, Amblyseius swirskii, or the minute pirate bug, Orius insidiosus. WFT may also pupate in the open flowers of certain plants with complex floral architectures, such as chrysanthemum. Pirate bugs are released onto ornamental pepper plants that are in flower which serve as a banker plant attracting the thrips and harboring the predators. Orius will feed on pollen in the absence of thrips and also other small pests such as spider mites and caterpillar eggs. This mite performs better during warmer temperatures (summer) and in addition to thrips, it also consumes whitefly eggs. Greenhouse IPM for Western Flower Thrips. But the key to implementing a successful biological control program is to release natural enemies early enough in the cropping cycle. Western flower thrips (Frankliniella occidentalis) prefer to feed on developing plant tissues such as growing tips and flower buds. Instead they feed within the mesophyll and epidermal cells of leaf tissues using a single stylet in the mouth, and then inserting a set of paired stylets, which lacerate and damage cell tissues and function to imbibe cell fluids. 2000. Ensure that greenhouse weed control is thorough - weeds harbor Western flower thrips and tomato spotted wilt virus. Adjacent crops such as grapes and citrus can also harbor thrips. Symptoms of WFT feeding include leaf scarring, distorted growth, sunken tissues on leaf undersides, and flower deformation (Figures 1 through 3). They release Orius on and around these planters. This will kill thrips on outdoor weeds and prevent them from entering the greenhouse to search for new hosts when weeds are mowed. However, the screening material for WFT is so fine that proper ventilation is a challenge and this limitation should be considered. Photos of INSV symptoms on greenhouse plants (scroll to see various crops). Photo of larvae. The first step in managing thrips is to prevent thrips from entering the greenhouse. Because of this, growers and researchers have been experimenting with the use of habitat planters for natural enemies. feet. In addition to the direct damage caused by WFT feeding, they may cause indirect damage by vectoring the tospoviruses: Impatiens Necrotic Spot Virus (Figure 6) and tomato spotted wilt virus. Another factor to consider is that due to the current trend of increased pest control material regulation combined with the increasing availability of low cost generic products and the excessive registration costs, growers are likely to see fewer new active ingredients registered for use against WFT and should develop management programs that maintain the effectiveness of currently available products. Plant Health July 2012Developing an Effective Western Flower Thrips Management Program By Raymond A. Cloyd. Screening can be used to mechanically exclude WFT. Control Of Thrips With Systemic Insecticides. Enhancing the activity of insect-killing fungi for floral IPM. The Orius will lay eggs in the same area where thrips lay eggs, usually in or near flowers. The following Orius program is suggested by Syngenta and Griffin Greenhouse Supply. Be sure to remove all weeds, which are reservoirs for WFT and potential inoculum sources for the viruses transmitted by WFT. This was also true for sunflowers, which were also susceptible to powdery mildew as well as thrips damage. Iris Yellow Spot is transmitted by onion thrips. August 1990, pp.1, 2, 3. Heinz, J.C. van Lenteren, A. Loomans, R. Wick, T. Smith, P. Lopes, J.P. Sanderson, M. Daughtrey, and M. Brownbridge. In all crops, soil drenches of nematodes such as Steinernema feltiae may be directed against western flower thrips pupae and prepupae in the soil. Thrips have spread throughout the horticulture industry on plugs, cuttings, and small plants. The spread of WFT and TSWV or INSV from grower to grower is caused in two ways: by shipping tospovirus-infected plants (both propagative and pre-finished) and by shipping plant materials infested with tospovirus-carrying WFT. W… However, western flower thrips is regarded to be a 'pesticide-induced problem', having developed resistance to pesticides from different chemical classes. Use an insecticide to knock-down emerged adults. The carbon dioxide will bring thrips out of their protected areas. ft of growing area. It is now established as a major pest in most parts of the world. Record thrips counts on cards and correlate this information to the damage you see on your crops. As the weather warms, make 3-4 weekly releases of 1 Orius per 10 sq. Western flower thrips, Frankliniella occidentalis P. (Thysanoptera: Thripidae) is a major agricultural and horticulture pest worldwide (Kirk, 2002; Kirk and Terry, 2003).It causes damage and spoilage to a vast number of economically important plant species through feeding, oviposition and spread of several plant diseases, most notably tospoviruses (Morse and Hoddle, 2006). Without viable alternatives for WFT control, the only means to prevent damage is … GPN recognizes 40 industry professionals under the age of 40 who are helping to determine the future of the horticulture industry. For example, in cut roses, removing all flower buds (including non-marketable flowers) can significantly reduce thrips populations … Pest control materials must be applied before WFT enter terminal or flower buds because once they do, it is very difficult to obtain adequate regulation and prevent injury. Seven species of thrips are vectors for TSWV, but the only confirmed vector for INSV is WFT. Resources from UMass Extension and the Center for Agriculture, Food and the Environment: ag.umass.edu/coronavirus. 16 and 18 in Lewis, 1997 for examples of thrips monitoring programs). Most insecticides and miticides affect insects and mites in specific ways. Box 128
Pesticides labeled for greenhouse use against WFT are listed in Table 1. Trap counts and keeping records are meaningful in two ways. Thrips are part of the order Thysanoptera, and are common garden pests that suck plant juices and sometimes spread viruses. Also, predatory mites (Transieus and Amblyseius species) and predatory thrips (Haplothrips) are common, but do not adequately control thrips populations, except under greenhouse conditions, where they are used as part of IPM programs. Control of western flower thrips is extremely difficult due to several biological characteristics of this species. This information is useful in determining the efficacy of a treatment or control measure. Sparta, MI 49345. Also, be sure to develop rotation programs that involve pest control materials with different modes of action (refer to Table 1). Using Predatory Mites to Manage Western flower Thrips in Bedding Plant Greenhouses. WFT are small (about 2.0 mm long) insects with piercing-sucking mouthparts. Adults have two sets of narrow, clear, nearly veinless wings that have dark, hairy, fringes. A contact insecticide such as horticultural oil can be used outside the perimeter of the greenhouse prior to mowing or using herbicides. WFT exhibit thigmotactic behavior, which means the body is in constant contact with a surface. There is no cure. The adults will move across the greenhouse and kill first and second instar thrips larvae and adult thrips. It has observed that the Cosmos "Sensation White" has been especially helpful in encouraging their Orius populations. Also, customers tend to have a higher tolerance for plant damage or are less scrutinizing than growers do. Read on for some practical and effective suggestions to manage these destructive pests. When chemical control is necessary, spray pesticides two to three times five days apart based on greenhouse temperatures ranging from 70-85°F. Amblyseius swirskii is another predatory mite being used. Also, plant propagators will have a lower tolerance threshold for thrips than finished plant growers. CULTURAL CONTROL Western flower thrips is more difficult to control than other thrips species because it develops rapid resi… updated 2012, 2015. WFT is the most prevalent species of thrips in Massachusetts greenhouses. Growers are encouraged to choose plant vendors with care. Thrips will move on air currents. management program will only work if you diligently scout your crops. Hsu C. and W. Quarles 1995. Establish thresholds (e.g., 10 to 20 adults per sticky card per week) for WFT adults, but be flexible, as these will likely change based on the crops grown, especially those that are susceptible to the viruses transmitted by WFT.