Department of Entomology, College of Agriculture, Food and Environment, University of Kentucky, Lexington, KY. (, Evaluation of onion germplasm for resistance to Iris Yellow Spot Virus (, Host-associated genetic differentiation in. Thrips feeding damage affects the leaf quality of green onions because of the formation of feeding scars.1Thrips are also a vector of the Iris yellow spot virus on onions. Treatment sequences are shown in the table under the figure. 2005b). larvae, minute pirate bug (Orius spp. 2014). Water loss from damaged leaf surfaces may cause stress and reduce plant growth and may accelerate leaf senescence, both of which may shorten the period bulbs enlarge. 1A). Some synthetic mulches also may repel insects. 2014). Determine the average true leaf stage and divide the number of thrips per plant to get number of thrips per leaf. Adults can y quickly when disturbed and also have a thicker cuticle (external covering) than larvae, which makes them more difficult to kill. A. botrytis L.), celery (Apium graveolens), cotton (Gossypium spp. For insect pest situations in Ontario, growers and stakeholders are encouraged to follow the crop update published by OMAF and MRA on ONvegetables.com. For instance, an action threshold level of 30 or more thrips per plant is suggested for the thrips-tolerant varieties, whereas a lower level of 1530 thrips per plant is suggested for susceptible cultivars (Cranshaw 2004). The threshold on dry cooking onions, leeks and Spanish onions is 1 thrips per leaf. Photograph by Joseph Ogrodnick, Cornell University. THRIPS: Thrips populations are beginning to build up in onion fields throughout the region. Treatments 7 and 8 suppressed thrips the best when comparing seasonal averages, but this was not statistically significantly different from treatments 3, 5 and 6. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. 9). Another study in India showed that C. menes parasitized onion thrips, but the range of parasitism varied from 2 to 18% during the season (Saxena 1981). To our knowledge, research has not been conducted with these mite species for managing onion thrips on onion. Severe damage to various crops has been reported in Africa, Asia, Europe, North and South America, and Australasia (Mound 1997, Boateng etal. However, because of the differences in spray recommendations for onion thrips and plant pathogens, it can be difficult for growers to implement a spray program that effectively combines both management approaches. Feeding on leaves also can create an entry point for plant pathogens (Orloff etal. Acknowledgements: We thank the cooperating onion grower who allowed us access to their field for the spray trial. Sticky cards are collected from the field after a certain period and then examined under a microscope to assess the presence and species of thrips (Mo 2006). 2013). 2014). In the 2022 growing season, researchers at Michigan State University tested the combination of synthetic conventional insecticides and fungicides at varying action thresholds to evaluate their ability to simultaneously manage onion thrips and Stemphylium leaf blight. 2001). For more information, visit https://extension.msu.edu. Part II available athttp://onvegetables.com/2013/06/28/onion-thrips-management-part-ii-management-options/. Thrips thrive in hot, dry weather, so you may need to shorten the time between scouting events. Onion thrips, T. tabaci, are easier to observe and count after opening the neck of an onion plant. The content of this article should not be substituted for the professional opinion of a producer, grower, agronomist, pathologist and similar professional dealing with this specific crop. In New York, 25 weed species supported reproductive populations of onion thrips, especially Brassica weed species such as Barbarea vulgaris Ait. Managing resistance to insecticides is critical given that this is the principal tactic used to manage thrips. 2013). In New York, the recommended action threshold is an average of three larvae per green leaf. 2008). In our 2-yr study, the incidence . 2013). In Greece, only arrhenotokous onion thrips populations successfully transmitted TSWV (Chatzivassiliou etal. Early detection of a pest problem is a key element for designing integrated pest management strategies. Predators of onion thrips are usually not in abundance until late summer when the majority of thrips feeding injury has already occurred (Fok etal. to onion, thereby causing bacterial bulb rot (e.g. Shearing stimulates thrips-susceptible new growth. A cumulative thrips-days (CTD) value is calculated by averaging the number of thrips per plant over two successive rating dates; then that number is divided by the number of days between ratings to determine the number of thrips per plant per day (thrips-days). rapa), tomato (Solanum lycopersicum), and practically all small grains (Pergande 1895, Parella and Lewis 1997, Cranshaw 2004, Shelton etal. Thrips. 1935, Passlow 1957). Adult females lay eggs in plant tissue, and the larvae that hatch feed on the leaf tissue (Figure 2).2There are two stages of feeding larvae (instars I and II) that collect under the folds of onion leaves or in the densely packed area where the leaves emerge from the neck of the bulb. Host plant resistance is another tactic that has received attention, but no onion cultivars that have a high level of thrips resistance are commercially available. Feeding damage from onion thrips can reduce yields considerably. In some cases, they may not be able to make it to the field to spray until a few days after scouting, so its beneficial for them to know if the counts are approaching the threshold. A.. Srinivasan R. Sundaraj S. Pappu H. R. Diffie S. Riley D. G. Gitaitis R. D.. Trdan S. Valic N. Zezlina I. Bergant K. Znidarcic D.. Ullman D. E. Cho J. J. Mau R.F.L. Quentin Tyler, Director, MSU Extension, East Lansing, MI 48824. Light blue sticky boards for mass trapping of onion thrips, Effect of mixed cropping on some insect pests of carrots and onions, Laboratory and greenhouse evaluation of a new entomopathogenic strain of. Published by Oxford University Press on behalf of the Entomological Society of America. You may also contact Customer Service at (830) 876-2430 or email customerservice@dixondalefarms.com. 2010). In England, mixed plantings or intercropping of carrots and onions effectively decreased onion thrips populations by 50% (Uvah and Coaker 1984). Thrips are some of the most damaging insect pests of onions. Research has shown that onion fields that are overhead irrigated have lower thrips populations than neighboring fields receiving furrow or drip irrigation.2, Natural predators can help manage thrips populations, most effectively later in the season when thrips are more exposed. The first and second instars are active feeding stages. Please switch to a supported browser: Chrome, Edge, Firefox, Safari. Under the worst case scenario, if one adult lays 100 eggs all of which hatch and develop into adults, in three generations there is the potential of 1,000,000 thrips! Enter your email address to subscribe to this blog and receive notifications of new posts by email. Onion thrips adults and larvae can be visually identified and counted more easily after opening the neck of the onion plants (Shelton etal. 1987). Knowledge of action thresholds for onion thrips can help onion growers optimize insecticide applications and other management tactics. Mulches suppress thrips populations by enhancing predator populations, creating barriers that prevent the resting stage larvae from accessing the soil, and lowering soil temperatures, slowing thrips development and population increase. 2003, 2006). The pest status of onion thrips can be attributed to its polyphagous nature, high reproductive rate, short generation time, high survival of cryptic (nonfeeding prepupa and pupa) instars, ability to reproduce without mating (parthenogenesis), ability to transmit plant pathogens, and development of resistance to insecticides (Morse and Hoddle 2006, Diaz-Montano etal. Scouting for onion thrips is critical to successful control because they are resistant to multiple insecticide classes. Severe feeding injury by onion thrips is also associated with tiny black tar spots, which is excrement from thrips (Fig. 2007). (, Bionomics, population dynamics and chemical control of thrips (, Control of organophosphate resistant onion thrips, 1986, Agricultural Experiment Station, Colorado State University, Variation for epicuticular waxes on onion foliage and impacts on numbers of onion thrips, Onion thrips (Thysanoptera: Thripidae): A global pest of increasing concern in onion, Characterization of resistance, evaluation of the attractiveness of plant odors, and effect of leaf color on different onion cultivars to onion thrips (Thysanoptera: Thripidae), Resistance to onion thrips (Thysanoptera: Thripidae) in onion cultivars does not prevent infection by, Economics of controlling onion thrips (Thysanoptera: Thripidae) on onions with insecticides in south Texas, Comparative development, reproduction and life table parameters of three population of. The graph below shows the results of the 2011 onion thrips insecticide trial conducted by the MSU Vegetable Entomology lab. Comparative efficacy of neem products, essential oils and synthetic insecticides for the management of onion thrips, Thrips management alternatives in the field, National Center for Appropriate Technology (NCAT), ATTRA - National Sustainable Agriculture Information Service Publication #IP132, USA. Damage appears as silvery patches or streaks on the leaves (Rueda and Shelton 1995; Figs. The adults also feed on and damage onion leaves. 2006, Kobayashi etal. 2008), and males are 0.7mm in length. Photograph by Brian A. Nault, Cornell University. Fail J. Shelton A. M.. Diaz-Montano J. After this, they siphon off the plant contents and consume mesophyll cells, which eventually results in a loss of chlorophyll and reduced photosynthetic efficiency (Boateng etal. 2011, Ganga Visalakshy and Krishnamoorthy 2012). These are very tiny insects. Treatments with insecticides reduced onion thrips populations by 50% when compared to the no-spray treatments, but only reduced onion thrips by 25% compared to the fungicide only treatment (Fig. Early detection is key to controlling this pest, as populations can explode quickly under ideal conditions. 2Schwartz, H.F. and Mohan, S.K. 7). Cal Poly strawberry research: Can robots kill pests? The tobacco thrips, Frankliniella fusca (Hinds), also may transmit IYSV, but transmission only has been shown to lisianthus, Eustoma russellianum (Salisbury), and not onion (Srinivasan etal. Thrips larvae feeding on an onion leaf. Onion thrips management Part I: Identification and Monitoring, http://onvegetables.com/2013/06/28/onion-thrips-management-part-ii-management-options/. PLEASE NOTE : We provide ONvegetables.com (Blog) free of charge and for information purposes only to individuals interested in commercial vegetable production. Insecticides are the primary method for controlling thrips on onions. For large onion fields (>2ha), 10 sampling sites with five plants per site (total of 50 plants per field) has been recommended (Rueda and Shelton 1995). 2009). Below we describe tactics that have been evaluated for thrips management in commercial onion fields. (, ENTFACT-317. Under conservative parameters, if a single female lays 25 eggs and 50% hatch, populations can explode up to ~1900 thrips in three generations. Carefully pull the onion leaves apart to count thrips. Egg stage is 5-10 days. A. cucumeris had a better numerical response compared with A. barkeri when feeding on onion thrips (Brdsgaard and Hansen 1992). Thrips feed by scratching on plant tissue with their mouthparts and sucking up the cell contents, which appears as silvering on the leaf tissue. 2005a), New Zealand (Martin etal. Even a single one is a thrips. 2003). In contrast, onion thrips attack potato, sweet potato, and mustard, but none are damaged to a level that would routinely cause economic damage. On onion, the average length and width of eggs are 0.23mm and 0.08mm, respectively (Patel etal. In some instances, arrhenotokous and thelytokous onion thrips populations can occur in the same field (Nault etal. 2014). In India, entomopathogenic fungi (Beauveria bassiana) were successful in reducing onion thrips populations and increasing onion yield (Singh etal. Arrhenotokous onion thrips that developed on onion produced more progeny and the population developed significantly faster on onion than on cabbage (Li etal. The high threshold treatments with 2 applications of Radiant was as effective as the low threshold treatments with Movento, Minecto Pro, and Radiant applied twice. Onion thrips are a major insect pest in onions. Older leaves that have been folded over may also be a preferred feeding site for the pest (Paibomesai etal. Start early! Only one end of the egg is in proximity to the tissue surface to allow emergence of immatures. Onion thrips have an extremely wide host range compared with other thrips species. 2013). The pupae are yellowish white, changing to yellow before adult emergence. At the Muck Crops Research Station in the Holland Marsh, onion thrips didnt reach action thresholds for treatment until the 19th and 20th of July in 2011 and 2012 , respectively; however, this may be earlier or later depending on the weather and your location in Ontario. The first part of this article will discuss why onions thrips are such a problem and how to scout for them, while the second part of the article will discuss management strategies. Some of the predators of onion thrips include Aelothrips spp., green lacewing (Chrysoperla spp.) The CTD is calculated by adding up the thrips-days on the latest sampling date. Inclusion of a penetrating surfactant is critical for improving the efficacy of insecticides that have systemic and translaminar movement within onion plants to control onion thrips (Nault etal. Heavy rains have been shown to wash onion thrips from plants (Harris etal. Incubation period is 45d on onion (Fekrat etal. Resistance can be mitigated by limiting the frequency of insecticide applications, rotating insecticides used in a sequence (based on groups or modes of action), and maintaining thorough coverage to prolong the effectiveness of insecticides (Gill and Garg 2014). Infestations that develop during the early stages of bulb formation have the largest impact on bulb size and quality. Another difference observed between arrhenotokous and thelytokous populations of onion thrips was the ability to transmit Tomato spotted wilt virus (TSWV), a Tospovirus closely related to IYSV (Chatzivassiliou etal. Regional and temporal variation in susceptibility to -cyhalothrin in onion thrips, Patterns of insecticide resistance in onion thrips (Thysanoptera: Thripidae) in onion fields in New York, Advances in control of onion thrips in cabbage (Thysanoptera: Thripidae), Evaluation of some botanicals and entomopathogenic fungi for the control of onion thrips (. This means two applications of Movento can be made to onions within a growing season, and these should be done consecutively, 7 to 10 days apart, for insecticide resistance management purposes. Adults lay eggs singly in the epidermis, nymphs feed on leaves, and pupation occurs in the soil. For example, in Taiwan, silver mulch was shown to repel thrips in seedling-stage shallots (Lu 1990). During the 2013 Muck Crops Conference in Bradford, Ontario, Dr. Mary Ruth McDonald, University of Guelph, presented valuable information about thrips management strategies under Ontario growing conditions. UC Pest Management Guidelines. Females can lay between 25 and 100 eggs. tomatoes, peppers, eggplants, sugarbeets, red beets, Travis Cranmer A reduction in green tissue negatively affects the onions ability to photosynthesize, and results in smaller bulbs and decreased yield. When thrips populations reach a certain threshold level, then the trap crop could be sprayed with an insecticide or disked under (Alston and Drost 2008). Transmission efficiency of IYSV to onion within and among populations of arrhenotokous and thelytokous onion thrips is not known. Whitney Cranshaw, Colorado State University, Bugwood.org. Onion thrips can reproduce asexually (parthenogenesis) and sexually. The key to minimizing losses caused by onion thrips will involve the combination of cultural and chemical controls, and use of resistant and tolerant varieties that suppress onion thrips populations and reduce feeding damage. 2012). Recommended number of sampling sites within an onion field varies in accordance with field size. 2006). (, Onion thrips management- Part I: Identification and monitoring, Effect of neem based botanicals, chemicals and bio-insecticides for the management of thrips in onion, Integrated pest management (IPM) in field crops, Characterization of a tospovirus isolate of, Cornell International Institute for Food, Agriculture and Development, Cornell University, Developing economic thresholds for onion thrips in Honduras, Observations on some predators and parasites of, Straw mulch and reduced-risk pesticides impacts on thrips and, Injury and control of onion thrips (Thysanoptera: Thripidae) on edible podded peas. Additionally, water stress may impact the nutritional quality of onion plants and also increases the attractiveness of the plants to thrips (Lewis 1973). Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is a well-known onion pest worldwide. Utah Pests Fact Sheet, Utah State University Extension. Thrips are most damaging to yields during the early bulbing stage. 2003, 2006). Figure 1. Chemical control Control through insecticides is difficult because of thrips' protected location in plants. White to pale yellow, elongate and slender body. In severe cases, IYSV may cause leaves to become necrotic and plants to mature prematurely (Fig. There are biological differences between onion thrips populations that reproduce via arrhenotoky and thelytoky. In NY, there could be 3 to 4 overlapping generations of onion thrips per year with infestation of onions starting in June, meaning that the onion crop, if planted in mid to late April and harvested early September, requires 6 to 8 weeks of protection. Scouting should be done by randomly sampling leaves or whole plants from four or more locations in the field, including field edges where colonization by thrips is likely to occur first. Thrips thrive when conditions are hot and dry. Field experiments in Colorado showed that straw mulch application to the center of onion beds at early to mid-bulb growth reduced thrips densities to 33% compared with nontreated plots of transplanted onions. To prevent further insecticide resistance, growers must rotate insecticide classes and implement action thresholds. These products differ in important characteristics such as their impact on bees and other beneficial insects, the minimum re-entry interval (REI), the minimum pre-harvest interval (PHI), the maximum number of applications per season, recommended frequencies of application, and the availability and use restrictions in each state. IYSV was first detected in Idaho in 1989, and by 2000 it was confirmed in most onion-producing areas in the United States and Canada. 2009). Other crops such as carrot, crucifers, cucurbits, and some owers (carnation, chrysanthemum) are highly attractive to onion thrips. In Ontario (Canada), insecticide resistance in onion thrips populations from onion fields was reported for -cyhalothrin, deltamethrin, and diazinon (MacIntyre-Allen etal. 2014). A. Also note, that pyrethroids are registered for thrips control on onions; however, Matador (lambda-cyhalothrin) and Decis (deltamethin) resistance was noted in muck growing regions in Ontario in the early 2000's. Use trap crops. Females lay eggs singly by inserting them into leaf tissue. Interestingly, there did not seem to be a straightforward correlation between the level of thrips control and onion yield, although treatments 7 and 8 had the highest yields among our treatments.
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