The bulk release formulation is more effective than sachets, however, some growers found that sachet packets provide more protection to the the mites. 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. Reduce the spray interval to 3 days if greenhouse temperatures are higher, and increase the spray interval to 7 days when greenhouse temperatures are lower. Adult WFT are about 1/16th of an inch long, and are long and narrow shaped, like grass seed. Growers are encouraged to choose plant vendors with care. Sprays applied to control thrips disrupt biological control of other pests such as twospotted spider mites, lygus bugs, whiteflies, and other insects. Enhancing the activity of insect-killing fungi for floral IPM. When tospoviruses are present in the saliva, these are transmitted to the plant during the feeding process in as little as 15-30 minutes. Amblyseius swirskii is another predatory mite being used. Control of western flower thrips is extremely difficult due to several biological characteristics of this species. Western flower thrips (WFT), Frankliniella occidentalis, is still one of the most destructive insect pests of commercial greenhouses feeding on a wide variety of horticultural crops. PDF: Developing an Effective Western Flower Thrips Management Program, SePRO Announces Personnel Moves for Next Phase of Growth, Proven Winners ColorChoice Brings Back Shrub Madness Bracket Competition, University of Florida Releases New Video on Monitoring Hydroponic Systems, What Consumers See in Their Gardens of the Future, Culture Report: New Guinea Impatiens Harmony Colorfall Series, Vaughan’s Horticulture Announces Sudden Passing of Matt Willoughby, UF to Host Virtual Field Day on Compact Vegetable Evaluation, EHR Strengthens Team with Former Gloeckner Reps. This insect order is composed exclusively of tiny insects commonly called thrips, and includes more than 7,000 species. Monitor for thrips as soon as plants or cuttings are received. You can also use the neonicotinoids including imidacloprid, acetamiprid, dinotefuran, and/or thiamethoxam. Tospovirus infections may be systemic (i.e., virus symptoms occur throughout the plant) or non-systemic (i.e., the virus symptoms are confined to a specific part of the plant). For example, avocado thrips and greenhouse thrips superficially scar avocado fruit skin. Thrips will move on air currents. Mode of action is the way a chemical works, so chemicals in different chemical classes may have the same or similar modes of action and be causes of pesticide resistance. Biological control agents must be released before Western flower thrips populations establish or reach outbreak proportions. • Use biological control agents such as predatory mites, predatory bugs, and possibly beneficial nematodes The following petunia cultivars are excellent indicator plants for the detection of tospoviruses: Calypso, Super Blue Magic, Blue Carpet, Cascade Blue, Summer Madness, Burgundy Madness, Red Cloud, Super Magic Coral. Managing vegetation in and around lettuce, biological control, and cultural practices are important in reducing the potential for damage from western flower thrips. Use a rate of at least one card per 1,000 sq.ft. Because of this, growers and researchers have been experimenting with the use of habitat planters for natural enemies. management program will only work if you diligently scout your crops. Usually one release onto the banker plants is all that is needed. Corporation) for his feedback regarding the industry perspective on managing WFT. Good sanitation controls Tospoviruses. 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. Place the cards just above the crop canopy in an even pattern throughout the entire greenhouse. Some thrips are beneficial because they kill other pests to your plants, so you want some thrips on flowers. Currently there are no recommendations for soil drenches aimed at thrips pupae. Eggs of this species are inserted into leaf, stem, or petal tissue, and are thus protected from insecticides. 1. WFT are small (about 2.0 mm long) insects with piercing-sucking mouthparts. It has observed that the Cosmos "Sensation White" has been especially helpful in encouraging their Orius populations. Canadian researchers also looked at castor beans, feverfew, gerbera, Lemon Gem marigold and sunflowers as potential banker plants. Fecal deposits (“thrips poop”) may be present on leaf undersides (Figure 5). When thrips are present on the lettuce crop, insecticides are often the only viable control alternative. Resources from UMass Extension and the Center for Agriculture, Food and the Environment: August 1990, pp.1, 2, 3. About 60-80 pirate bugs can be released per flowering pepper plant. Thrips spot unique asymmetrical mouthparts. Control Of Thrips With Systemic Insecticides. Discard tomato spotted wilt virus infected plants. This is vital to the development of an effective and “sustainable” WFT management program. Begonias and poinsettias are much less susceptible to damage and thresholds are much higher. The eggs of WFT are well protected and in general, pesticide sprays are ineffective against them. 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. Mention of a pesticide does not constitute an endorsement of any product and any omission from this list is unintentional. A general knowledge of WFT biology is essential to understand the challenges associated with developing an effective management program. By stimulating feeding, the thrips had more contact with infected spores on treated leafs, resulting in better control. Stack New England Greenhouse Floriculture Guide, A Management Guide for Insects, Diseases, Weeds and Growth Regulators. Larvae rese… Although WFTs have piercing-sucking mouthparts, they do not feed exclusively in the phloem sieve tubes like aphids and whiteflies. For example, in cut roses, removing all flower buds (including non-marketable flowers) can significantly reduce thrips populations … In fact, most consumers don’t even know what a WFT is. During feeding, saliva is injected into the plant cell and the contents withdrawn. Monitoring . Open, weedy land adjacent to orchards should be disced as early as possible to prevent thrips development and migration of adults into orchards. Be sure to remove all weeds, which are reservoirs for WFT and potential inoculum sources for the viruses transmitted by WFT. 6 Elkhart, Indiana, For more information see fact sheet: Diagnostic Test Kits, Another option for detecting tospoviruses is to send a plant sample to a plant disease diagnostic clinic. Screening can be used to mechanically exclude WFT. Ornamental pepper plants have been used  in spring crops as banker plants at a rate of one plant per 1,000 sq. This will kill thrips on outdoor weeds and prevent them from entering the greenhouse to search for new hosts when weeds are mowed. Yellow sticky cards are best used for general pest monitoring because they are also attractive to whitefllies, winged aphids, leafminers, fungus gnats and shoreflies. Solabiol Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Indicator plants and sticky cards are the best available means of providing early warning of thrips and TSWV/INSV in greenhouse production areas. Some plant species die from the virus, while others survive, but are unsalable. Pesticides are often used to control western flower thrips ( Frankliniella occidentalis) in horticultural crops. Check plants each day, looking for WFT feeding scars, which are whitish and have an irregular outline. Try not to overfertilize plants, as this can lead to more thrips damage. Keeping records over time will provide information on what direction the population is changing and at what rate. WFT population monitoring is necessary to detect incipient WFT problems in crops and to determine if control actions have been effective (see Chs. The only way to maintain WFT populations at “low” levels are by timing of applications and thorough coverage of all plant parts. Use an insecticide to knock-down emerged adults. 16 and 18 in Lewis, 1997 for examples of thrips monitoring programs). Biological Control of Western Flower Thrips. This article is intended to provide applicable information so growers can develop effective strategies in dealing with WFT. Different crops have different susceptibilities. We believe that WFT do not overwinter outdoors in Massachusetts but WFT are known to overwinter in soil and clover in the Mid-Atlantic states and southern Pennsylvania. However, the screening material for WFT is so fine that proper ventilation is a challenge and this limitation should be considered. Western flower thrips control in spring bedding plants: which formulation is best? 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. To delay resistance, use a given effective insecticide for 2-3 pest generations of WFT (2-3 weeks, depending on the season), then rotate to another insecticide with a different mode of action. Because Orius is slow to establish in the greenhouse, different types of banker plant systems have been investigated to encourage this predators  development and establishment in the greenhouse. Thrips feed by piercing plant cells with their mouthparts and sucking out their contents. Box 128 Instead, use pest control materials with broad modes of activity such as Beauveria bassiana alone, or mixed with azadirachtin, insecticidal soap, horticultural oils, or insect growth regulators such as novaluron. Eggs and pupal stages are unaffected by pesticide sprays, so make sure the spraying program lasts long enough to control newly emerged larvae and adults. Also, customers tend to have a higher tolerance for plant damage or are less scrutinizing than growers do. For example, Saintpaulia is very susceptible and treatment thresholds are lower than 5-10 thrips/trap/week. Consider treating only if populations reach 10 thrips per blossom (UC-Davis). However, it is important to note that any WFT Thrips are often attracted to weeds blooming on the orchard floor. 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. Three to five applications in a seven to 10-day period may be needed to obtain sufficient kill when WFT populations are “high” and there are different life stages (eggs, nymphs, pupae, and adults) and/or overlapping generations present, which occurs mainly from spring through late fall. Treatment decisions should be based on scouting records that include numbers of thrips, not only on the presence or absence of thrips. This mite performs better during warmer temperatures (summer) and in addition to thrips, it also consumes whitefly eggs. Identifying the species of thrips may reveal that it is harmless in certain situations and no control action is needed. The first step in managing thrips is to prevent thrips from entering the greenhouse. Recent research in Canada reported  that the cultivar "Purple Flash" was more effective as a banker plant than the ornamental pepper variety "Black Pearl" which has been used over the past few years for this purpose. The eggs hatch into larvae, which usually remain protected in flower buds 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. Organic sprays, such as natural pyrethrum (e.g. Adults however, do not transmit the virus to their young and there is no transmission from adult to egg. 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. **The author would like to acknowledge Joe Chamberlin (Valent U.S.A. You can have the best pest control materials at your disposal but if you don’t use or apply them correctly they will not be effective. Sometimes flower buds abort. Place Amblyseius cucumeris slow release sachets in hanging baskets that cannot easily be reached. Silvery leaf scars and specks of black feces are a good way of diagnosing the presence of WFT on plants. The adults will move across the greenhouse and kill first and second instar thrips larvae and adult thrips. All rights reserved. Thrips can devastate fields and reduce yields as much as 50 percent. Weeds serve as host for WFT and INSV and managing weeds inside and outside the greenhouse is critical for thrips management. Van Driesche R.G., K.M. Pepper plants attract the thrips and also serve as indicator plants for early detection. The second instar nymphs migrate to the base of a plant and enter the growing medium to pupate. This year, growers have had even more reason to worry about thrips, since Iris yellow spot virus was recently discovered in California. Using Predatory Mites to Manage Western flower Thrips in Bedding Plant Greenhouses. It is difficult to diagnose tospovirus infections of greenhouse plants using visual symptoms alone. But the key to implementing a successful biological control program is to release natural enemies early enough in the cropping cycle. Biological control of western flower thrips, in general, can be very difficult or more challenging than using insecticides. Because the prepupae and pupae are mostly in the soil, these stages are not affected by insecticides applied to the foliage. L.B. Damaged plant cells collapse, resulting in deformed plant growth, flower deformation, or silvered patches and flecking on expanded leaves. If a plant is suspected of being infected with a tospovirus because the plant is showing symptoms of virus infection, a tissue sample can be collected from those parts of the plant showing symptoms. This will avoid unnecessary applications of pest control materials, which reduces selection pressure and thus the potential for resistance. The egg stage lasts from 2-1/2 to 4 days. Table 1. Also, plant propagators will have a lower tolerance threshold for thrips than finished plant growers. Photos of INSV symptoms on greenhouse plants (scroll to see various crops). Adults have two sets of narrow, clear, nearly veinless wings that have dark, hairy, fringes. 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. Vitax Plant Guard Pest & Disease Control, Bug Clear for Fruit and Veg) can give good control of thrips. In cotton this species was found to be a predator of spider mite eggs (Gonzalez and Wilson 1982, Hunter and Ullman 1989, Kindt et al. 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. Adjacent crops such as grapes and citrus can also harbor thrips. New England Floriculture Inc. (. Record thrips counts on cards and correlate this information to the damage you see on your crops. Orius will feed on pollen in the absence of thrips and also other small pests such as spider mites and caterpillar eggs. As the weather warms, make 3-4 weekly releases of 1 Orius per 10 sq. Only the two larval instars of WFT can acquire the virus. In addition to using pest control materials, there is always the option of purchasing and releasing biological control agents (predators and benefical nematodes). Control is usually not necessary because western flower thrips rarely cause economic damage at densities that typically occur in strawberry fields. The following Orius program is suggested by Syngenta and Griffin Greenhouse Supply. In one study, white sugar added to Beauveria bassiana (Botanigard) increased mortality by 20 percent. Therefore, blue cards are best used in thrips-sensitive crops. Western flower thrips will also ingest the contents of pollen grains. P.O. Photos of feeding injury. Iris Yellow Spot is transmitted by onion thrips. Pear thrips (Taeniothrips inconsequens) Western flower thrips (Frankliniella occidentalis) . Tolerance levels will vary depending upon the crop, its stage of growth, local market standards and whether or not either INSV or TSWV are present at the site. Life Cycle drawing credit: See references - Sanderson J.P. 1990. Almost all greenhouse crops are susceptible except for poinsettias and roses. One common question asked by greenhouse producers is associated with the effectiveness of systemic insecticides against the western flower thrips, Frankliniella occidentalis. Remove "pet" plants and avoid keeping leftovers such as holiday cacti and cyclamen. Western flower thrips attack a wide range of plants including: carnations, chrysanthemums, corn, cotton, cucumbers, eggplants, gerberas, grapes, impatiens, melons, peaches, peanuts, peas, and peppers. Remove all plant debris on benches and floors. Fava bean plants can also be used as an indicator plant. Long Island Horticulture News. They are used in biocontrol programs when the weather warms in spring and beyond, in addition to other biocontrol agents already being used. While resistance is of concern, failure of chemical control is most often due to poor timing, poor coverage or other factors and these causes should be considered before assuming resistance. For instance, at full maturity, onion thrips and western flower thrips are larger than citrus thrips and avocado thrips. Adding sugar may cause more feeding injury if the insecticide is not effective. Both companies have separate kits available for testing for INSV and TSWV. Flower-feeding thrips are routinely attracted to bright floral colors, especially white, blue, and yellow, and will land and attempt to feed. Reflective mulches can help to hide your plants from thrips. Depending on environmental conditions and nutrient levels, WFT females lay 150-300 eggs during their lifetime. Other agents show promise as biological pest control, including the fungus Metarhizium anisopliae, and the mirid Dicyphus hesperus. The pupal stage does not feed and is very tolerate or immune to most pest control materials used to regulate WFT nymph and adult populations. 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. Certain biological attributes of this insect predispose it to be a direct pest across a wide range of crops. However, research by Raymond Cloyd, Kansas State University showed that the addition of brown sugar and other sweeteners to lure thrips from hiding does not work and in some cases can cause the growth of black sooty mold. Brownbridge M., M. Skinner and B. L. Parker. Note that it has been reported that populations of WFT have shown resistance to Conserve®. 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. 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. In all crops, soil drenches of nematodes such as Steinernema feltiae may be directed against western flower thrips pupae and prepupae in the soil. Some growers make the mistake of rotating after each treatment, which will increase resistance. different age structures or life stages simultaneously over the course of the crop production cycle. 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). updated 2012, 2015. 2000. (Release rate: 10 mites per square foot). Also, screening will only be helpful if the source of infestation is from thrips migrating in from the outside and not from infected plant material within the greenhouse, which is most common. A contact insecticide such as horticultural oil can be used outside the perimeter of the greenhouse prior to mowing or using herbicides. Western flower thrips (WFTs) are difficult to control for several reasons. Below are some key points to contemplate when implementing a pest management program against WFT: • The first line of defense in any pest management program is sanitation. As long as the pepper plants are in flower and producing pollen, the minute pirate bugs will reproduce on the banker plants. Both adults and nymphs may aggregate in flowers or other concealed locations on plants; however, adults (particularly females) prefer to feed on pollen. Seven species of thrips are vectors for TSWV, but the only confirmed vector for INSV is WFT. The life cycle consists of an egg stage, two nymphal stages, two pupal stages and an adult. • 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. WFT damage plants directly by feeding, and indirectly by acting as vectors for the tospoviruses impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV). The vigour of the plant is reduced by loss of chlorophyll. Thrips can also be collected from sticky traps and tested using the test kits. The carbon dioxide will bring thrips out of their protected areas. Orius insidious (Pirate bug) is a generalist predator feeds upon thrips, spider mites and pollen. 75 Applewood Drive, Suite A GPN recognizes 40 industry professionals under the age of 40 who are helping to determine the future of the horticulture industry. 1998. Ideally, insecticides should be applied with equipment that produces very small spray particles (<100 microns). • Use pest control materials with broad modes of action early in the crop production cycle and if populations are starting to increase (based on numbers of WFT captured on sticky cards) then incorporate pest control materials with site-specific modes of action. The pesticide label is the ultimate authority for pesticide use. Thrips are part of the order Thysanoptera, and are common garden pests that suck plant juices and sometimes spread viruses. Thrips will preferentially feed on flowers, but flowers do not show virus symptoms and will attract WFT away from the leaves. WFT prefer to feed on flowers, so the longer a crop can be grown without flowering the lower the thrips population will be. University of Massachusetts, Amherst • Scout crops routinely using colored (yellow or blue) sticky cards. Symptoms vary depending on plant species, cultivar, developmental stage of the plant, and environmental conditions. See section on monitoring. It has also been suggested to add a breeder pile of the predatory mite Amblyseius cucumeris to habitat planters to feed on the thrips attracted to the the pollen source while Orius populations grow. Plant Health July 2012Developing an Effective Western Flower Thrips Management Program By Raymond A. Cloyd. Attach cards to a stake with a clothespin so that cards may be raised as the plants grow. Samples may be sent to the University of Massachusetts Plant Disease Diagnostic Lab, 101 University Drive, UMass, Amherst, MA 01003 (a fee will be charged). Hsu C. and W. Quarles 1995. Apply Hypoaspis miles (or Hypoaspis aculifer) to media. Lyon S. 2002. Of the ten known types of tospoviruses, only two-TSWV and INSV-infect ornamental plants, but both infect over 600 species of ornamental plants. Floral Facts, University of Massachusetts, Amherst, MA. The maxillae then ingest the fluids from the cells, but not directly from the vascular tissue. These are the two stages that acquire the tospoviruses (mentioned below), which are then transmitted by adults. Applications conducted after flowers open are, in general, too late since damage has already occurred. Small droplet sizes are best because they penetrate better into the protected areas of the plant where the thrips are found and can provide better control if coverage is thorough. Effective sanitation will reduce or even eliminate thrips as a pest problem. Pest description and crop damage Adult western flower thrips (WFT) are very small (about 0.04 inch long at maturity), slender insects with fringed wings. Once you start seeing an increase in numbers on the sticky cards, which may be above your established threshold (e.g., 10 to 20 adult WFT per sticky card per week), then you may need to use a different set of pest control materials including abamectin, acephate, methiocarb, spinosad, chlorfenapyr and/or pyridalyl to ‘knock down’ populations. 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. Adult male WFT are light yellow, while adult female WFT are a little larger than the males and vary in color from light yellow, yellow with brown splotches, to dark brown. In addition to resistance, there are other reasons for poor regulation of WFT populations when using pest control materials including 1) using the wrong pest control material (this does happen); 2) spray timing, which is associated with the age structure of WFT populations (again, scouting will avoid this problem); 3) spray coverage (especially when using contact pest control materials); 4) pH of the spray solution; 5) frequency of applications; and 6) migration of WFT populations into greenhouses from outdoors, which may have already been exposed to a similar mode of action that will be used in the greenhouse. Overlapping generations of thrips within a greenhouse may result in continuous virus transmission. Western flower thrips can be difficult to manage for a number of reasons. Winged adults are weak fliers but may be carried on air currents and employee's clothing. Frankliniella occidentalis– known as Western Flower Thrips or Californian Thrips, is a small insect originating on the West Coast of North America, which spread through much of Europe in the 1980’s as a consequence of the international trade in plants. First and foremost, to effectively manage WFT, it is critical to develop a scouting program, which combines the use of yellow or blue sticky cards to monitor adult population trends, and visual inspection of crops to assess infestation levels of the nymphal stages. These individuals are today’s movers and shakers who are already setting the pace for tomorrow. MOA group numbers are found on many pesticide labels and are listed below for selected materials listed for managing WFT. 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. (Release rate: 10 mites per square foot), Apply Amblyseius cucumeris in bulk formulation to flats and benchtop pots, and to easily reached hanging baskets. Western Flower Thrips Biology and Control. Labor will be saved if this is done when baskets are being hung. Most insecticides and miticides affect insects and mites in specific ways. However, if INSV or TSWV is present, the tolerance levels for thrips is zero and a strict thrips control program should be implemented. Continue to monitor WFT population levels to determine if additional pesticide applications are necessary. The IPM Practioner 17(4) pp 1-11. W… WFT will also eat mite eggs, adult mites, other thrips. Keep flowers off of plants as long as possible to reduce populations. The key to WFT management with pest control materials is to initiate applications when populations are “low,” which avoids having to deal with Therefore, repeat applications are typically warranted to kill the life stages that were not affected by previous applications. It is now established as a major pest in most parts of the world. 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. Toward the end of the second larval stage, the thrips stops feeding and drops or enters the soil or leaf litter and becomes a prepupa, which is a nonfeeding stage that lasts one or two days before pupation. Tospovirus symptoms often mimic symptoms caused by other problems such as nutrient deficiencies. Larvae are very tiny and difficult to distinguish without magnification. To set up a monitoring program using petunias, first remove flowers. These ways may be called the pesticides "mode of action". To prevent driving thrips into the trees, do not disc the cover crop when trees are in bloom. Use a blue non-sticky card to attract thrips to indicator plants since WFT are more strongly attracted to blue than to other colors. This was also true for sunflowers, which were also susceptible to powdery mildew as well as thrips damage. Tospoviruses, however, may be present even though the plant shows no symptoms. Adult WFT do not acquire the virus from tospovirus-infected plants because tospoviruses pass right through the gut and do not enter the salivary fluid. Also, be sure to develop rotation programs that involve pest control materials with different modes of action (refer to Table 1). Based on scouting records that include numbers of thrips feeding scars within three days, depending temperature... 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