Factsheet 14/09 Horticultural Stoneleigh Park Development Kenilworth Protected ornamentals Company Warwickshire CV8 2TL T: 0247 669 2051 E: [email protected]

Thrips control on protected ornamental crops Jude Bennison, ADAS

Thrips are an important pest of ornamental bedding , pot plants and cut . They cause direct feeding damage and some species can also transmit viruses. This factsheet provides guidelines on the recognition of native and quarantine thrips species, the damage they cause and information about their biology and control.

Action points • Practice good nursery hygiene and • Keep up to date with current biolo- weed control to minimise sources gical and chemical control options. • Learn to recognise thrips adults on of infestation. sticky traps, and both thrips adults • Only use a pesticide if necessary, and larvae on plants. • Plan and start biological pest selected according to the thrips control programmes before thrips/ species present and whether or • Be aware of the thrips species feeding damage are seen. not an IPM programme is in place. present on the nursery (confirmed by an entomologist). • Monitor traps and plants regularly. • If a quarantine thrips species is suspected, contact Fera, • Learn to recognise thrips feeding • Pay particular attention to fav- Health and Seeds Inspectorate damage and symptoms of thrips- ourite host plants and bought-in immediately (see further information transmitted viruses. plant material. section).

Introduction by their feeding can make plants UK protected ornamental crops is unmarketable. It is important to know the western thrips (WFT) Thrips are one of the most serious which thrips species are present on (Frankliniella occidentalis), which is pests of protected ornamental the nursery, in order to use the resistant to many pesticides. On orna- crops, feeding on a wide range of most effective control strategy. For mental crops, WFT damages leaves, plant species. Damage caused example, the main species damaging flower buds and (Figure 1).

1 Typical damage to caused by western flower thrips feeding Thrips recognition Adults can live for several weeks. stage lasts for about 10 days at 20°C lasts for about five days at 20°C and Life stages and can occur on foliage plants, On chrysanthemum, they live for and five days at 25°C, but develops three days at 25°C. When pupation E. americanus adults (Figure 6) are including citrus, chamaedora, and biology about 75 days at 20°C and 31 days more slowly at lower temperatures. is complete, the adult thrips emerges more obvious to the eye than WFT croton, dracaena, ficus, kentia palm, at 25°C. The temperature ‘threshold’ When fully grown, most of the from the pupal case. (females are up to 2 mm long). stephanotis and tradescantia. The Although expert microscopic exa- for WFT flight is 20°C. late second stage larvae drop from Adults are dark brown to black, adults are brown and the wings look mination is often needed to the plants to pupate in the ground, WFT development and survival with distinctive pale areas at the pale with a dark band across them, confirm the exact thrips species, Eggs growing media or substrate. However, WFT are more of a problem between bases of the wings, giving the thrips giving a striped appearance. The certain features such as colour Like those of other thrips species, a small proportion may pupate on the spring and autumn, but breeding the appearance of having pale larvae are white and translucent. of the adults or larvae can help WFT eggs are not visible as the plants, in sheltered places such as can continue all year on host plants ‘shoulders’. The larvae and pupae are in recognition. WFT is described females lay them into plant tissue. on the undersides of lower leaves, in heated glasshouses (eg on AYR whitish-yellow and paler than those Glasshouse thrips (Heliothrips in detail below, and other relevant or hidden in flowers. chrysanthemum). WFT can develop of WFT or onion thrips. Unlike WFT haemorrhoidalis) species are described briefly to Larvae between 10°C and 35°C. However, or onion thrips, E. americanus always This originally tropical species is help to distinguish them from WFT. WFT larvae (Figure 3) hatch from the Pupae WFT can survive in a quiescent state pupates on the leaves. also established under glass Information is also given on eggs after a few days, depending Like other thrips species, WFT has at lower temperatures over the winter in the UK and sometimes occurs thrips biology and behaviour, as on temperature. On chrysanthemum, two pupal stages; the prepupa and in soil, on plants or on plant debris, Banded-winged palm thrips on protected ornamentals. It is not this knowledge can help to plan at fluctuating summer temperatures the pupa, neither of which feed. Both in glasshouses, tunnels, or outdoors. (Parthenothrips dracaenae) a quarantine pest. It feeds mainly control strategies. of 18.5°C night and 36°C day, they these stages are yellowish and about At typical summer glasshouse fluc- This species is not native to the UK on foliage and pot plant hosts hatch after three days. There are two 2 mm long. The prepupa has short tuating temperatures, WFT develop but is not a quarantine pest. It including orchids and palms, and larval stages, neither of which have immature wings and short, forward- from egg to adult in only 11 days. The is established under glass and has even been found on some ferns. Native or established thrips wings. First stage larvae are less pointing antennae. The prepupal pest can therefore breed very quickly in internal landscaping in the UK The pest has also been recorded on species than 1 mm long and colourless or stage lasts only for a day or two then during the summer and can go white. They feed for two or three days develops into the pupa which has through many generations per year, Western flower thrips (WFT) before developing into the second longer immature wings and longer particularly in heated structures. (Frankliniella occidentalis) stage larvae which are about 1 mm antennae which fold backwards over WFT was introduced to the UK on long and yellow. The second larval the body. The pupal stage (Figure 4) Onion thrips (Thrips tabaci) infested plant material in 1986 and The onion thrips is native to the since then has become widely UK. It is a common pest of outdoor established, mainly on protected vegetable crops such as onion and crops, but also on some outdoor leek, in addition to many protected crops such as strawberry. WFT edible and ornamental crops. is no longer a notifiable, quarantine Although WFT is now usually the pest in the UK. predominant species on protected crops, onion thrips is still frequently Host plants found. Bedding, pot plant and cut WFT is a major pest of many flower hosts are the same as those 4 Western flower thrips pupa protected edible and ornamental listed for WFT. crops. Common flowering bedding and pot plant hosts include Life stages brachycome, chrysanthemum, Onion thrips can look very similar to cineraria, cyclamen, dahlia, fuchsia, WFT. In the UK, the adults (Figure 5) impatiens, ivy-leaf geranium, primula are always female and vary in colour and verbena. Cut flower hosts include from greyish yellow to brown. First alstroemeria, chrysanthemum, dahlia, stage larvae are colourless or white. gerbera and lisianthus. Foliage 2 Western flower thrips adult female Second stage larvae tend to be plant hosts include ficus, maranta, greenish, rather than yellow as in palms and radimachera. Weed hosts WFT. Adults and larvae feed on include chickweed, clover, groundsel, leaves and in flowers, and the older mallow, shepherd’s purse and thistle. larvae drop to the ground to pupate. 5 Onion thrips adult Adults Echinothrips americanus Like other thrips species, WFT adults This species is not native to the are small, slim insects, with narrow UK but is not a notifiable quarantine wings fringed with hairs. Female pest. It was first confirmed in the WFT (Figure 2) are slightly larger UK in 1995, on syngonium imported (1.5 to 2 mm long) and darker than from the Netherlands. Since then, the males. The females usually have it has occurred under glass at a yellowish head and front half of many UK sites, usually on foliage the body and a brownish back half. plants including dieffenbachia, The males are yellowish all over. fatsia, ficus, philodendron and WFT adults can be found on upper spathiphyllum. It has also been or lower sides of leaves but prefer to recorded on chrysanthemum, feed in flowers or buds if present. 3 Western flower thrips larva impatiens and poinsettia. 6 Echinothrips americanus adult begonia, chrysanthemum and , which was Damage caused by necrotic leaf spots, necrotic If the presence of a notifiable pest fuchsia but is not a common pest suc-cessfully eradicated in 2001. thrips-transmitted viruses streaks on stems, plant stunting or disease is suspected, you must of these plants in the UK. The adults However, Fera Plant Health and and flower distortion. Further details immediately inform Fera PHSI are dark brown to black (occasionally Seeds Inspectorate has repeatedly WFT and onion thrips can transmit about IYSV are provided in the HDC (see Further Information Section). bicoloured with an orange-yellow intercepted the pest on various plants tospoviruses, introduced to the Factsheet 19/08, ‘Iris Yellow Spot abdomen) with pale wings, and the and produce and there is a continued nursery either via infected plant Virus: A potential threat to the onion larvae and pupae are whitish-yellow. risk of importing it on cuttings and material, then spread by resident industry’. IYSV is notifiable to Fera The larvae often have a large round plant material. The adults are small thrips vectors, or via immigrating PHSI whenever found or suspected. droplet of reddish or black fluid at the and yellow (Figure 8), about 1 to viruliferous adult thrips flying from end of the body, which drops onto 1.3 mm long. The larvae are creamy nearby infected crops. the leaf and can lead to the growth yellow to pale orange and drop to of sooty moulds. the ground to pupate. T. palmi does • Tomato spotted wilt virus (TSWV) not disperse well and is likely to be and Impatiens necrotic spot virus Grain thrips (Limothrips spp.) spread on infested plant material (INSV) are currently the most Grain or cereal thrips, (eg Limothrips rather than by adult flight. The pest important tospoviruses in the UK. cerealium) often fly into glasshouses is unlikely to survive the UK winter 7 Grain thrips adult on yellow sticky trap In the UK, the thrips vector for during the summer, particularly outdoors. both viruses is WFT. First stage during harvesting of nearby cereal WFT larvae acquire the virus when crops. They are commonly known Chilli thrips (Scirtothrips dorsalis) they feed on infected plants, and as ‘thunderflies’ or ‘thunderbugs’ The chilli thrips or yellow tea thrips when they become adults they as they take flight in large numbers in is a notifiable quarantine pest. It has transmit the virus to other plants warm, humid conditions. The adults not been detected in UK nurseries, during feeding. There is a wide are dark brown or black (Figure 7) but at the time of printing there was range of ornamental host plants and are easily distinguished from an ongoing outbreak under glass for the TSWV virus including WFT or onion thrips on sticky traps. in a botanical garden in the south aster, chrysanthemum, cineraria, 10 Small black specks of thrips faeces are often visible within the bleached areas of leaves Grain thrips do not breed on bedding, of England. The pest is native to cyclamen, dahlia, fuchsia, and petals affected by thrips pot plants or flower crops. Asia but in recent years has started impatiens, ivy-leaf geranium, lily, to spread rapidly across the world, nemesia, primula, ranunculus and including to Africa, Israel, the verbena. More recently, INSV has Quarantine thrips species Caribbean, North and South America. also been confirmed on a more Fera PHSI has repeatedly intercepted 8 Melon thrips adult restricted host range, including The following two thrips species the pest since 2005 on produce from chrysanthe-mum, cineraria, are not native to the UK and are India and Kenya, and also from coleus, dianthus, diascia, fuchsia, quarantine pests, notifiable to Fera St. Lucia and Thailand. S. dorsalis lobelia, nemesia and verbena. Plant Health and Seeds Inspectorate has a wide host range including Symptoms of both viruses include (PHSI) whenever found or suspected both edible and ornamental plants. chlorotic or necrotic leaf spots, (see Further information section). Ornamental hosts have included leaf rings, leaf line patterns, chrysanthemum, dahlia, hydrangea, distortion, bronzing, yellowing and Melon thrips (Thrips palmi) and . S. dorsalis adults (Figure 9) necrosis, stem blackening and The melon thrips is a serious pest are small, about 1 mm long, with growing point death (Figure 12). in Asia and parts of Australasia, pale yellow bodies and wings that Outbreaks of both viruses are now the USA, the Caribbean, South appear dark when at rest against the less prevalent than in previous America and Africa. T. palmi body. The larvae are pale. The larvae years, probably due to improved has a wide host range, including pupate both in the ground and on the methods of WFT control. 11 Typical young leaf distortion caused by thrips feeding (fuchsia leaf) chrysanthemum, ficus and plants. The pest is unlikely to survive orchids. So far there has been the UK winter outdoors. • Chrysanthemum stem necrosis only one outbreak in the UK, on 9 Chilli thrips adult virus (CSNV) is also spread by WFT but there has been only one case in the UK. Symptoms included dark stem lesions and Thrips damage areas (Figure 10). Feeding in leaf and WFT, T. palmi tends to feed on upper some leaf necrosis. The infected flower buds can also cause distortion leaf surfaces rather than in flowers. crop was removed and the virus symptoms and stunting (Figure 11). Damage can The quarantine pest S. dorsalis eradicated. CSNV is notifiable downgrade plants or render them feeds on young leaves, flower buds to Fera PHSI whenever found Direct feeding damage unmarketable, and severe infestations and fruits, causing scarring, malfor- or suspected. can cause significant plant losses. mation, curling, blackening and Feeding by thrips adults and larvae The quarantine pest T. palmi feeds shrivelling. Severe infestations can • Iris yellow spot virus (IYSV) on leaves and petals causes small on leaves (initially along the midrib and cause total defoliation and heavy was confirmed for the first time white or silvery flecks or patches, veins), stems and flowers, causing crop losses. in the UK in 2007, on lisianthus. which later turn brown and necrotic. silvery scars, distortion, yellowing and The vector of IYSV is the onion Small black specks of thrips faeces stunting. Severe infestations can thrips, Thrips tabaci. On lisianthus, are usually visible within the bleached kill plants. On chrysanthemum, unlike IYSV symptoms include pale 12 Typical symptoms of tomato spotted wilt virus on impatiens Sources of particularly where host crops are • Soil, growing media, used matting, susceptible plant species every bagsr o covered containers, sited are summarised below. Choice, present all year round. This is the pots and trays containing thrips week throughout the production as far away from the glasshouse combinations, timings and rates of infestation most common source of the main pupae. period. as possible, before taking the release or application within an IPM thrips pest (WFT). covered skips or trailers to a local programme should be planned Considering possible sources • Adjacent infested crops or infested • Thrips can be present on the authority disposal site. carefully. If necessary, seek advice of thrips is very important when • Bought in cuttings or young crops in nearby structures. upper or lower sides of leaves from the supplier or a specialist planning thrips management plants infested with thrips or eggs. and in growing points, buds and • Ideally use new pots, trays and IPM consultant. The information given programmes. Sources of infestation Importing plant material increases • Weed hosts. flowers. A useful method for matting for each crop, or sterilise below refers mainly to WFT and include: the risk of quarantine thrips species. monitoring WFT is to tap young any to be re-used. onion thrips, which has a very similar growth and flowers onto a white biology to WFT. • The resident population in the • Plant debris from previous infested plastic tray or white paper on a • Sweep, pressure wash and disinfect glasshouse or polythene tunnel, crops. clipboard. Any dislodged thrips benches and concrete floors Amblyseius cucumeris adults and larvae can be seen on between crops. This predatory mite is the main bio- the tray or paper. logical control agent used against • Soil steaming for sterilisation thrips in the UK and it can give Integrated thrips are more easily seen on yellow to aid early detection and help indicate • Look for direct damage symptoms (eg between successive very good control of WFT on bedding, than blue. Yellow traps are also population increases (Figure 13). such as white flecking on leaves chrysanthemum crops), will reduce pot plants and cut flower crops. management useful for monitoring other pests, or petals, distorted young leaves, the risk of thrips survival in the soil. A. cucumeris can develop between eg leaf miners and whiteflies. • A sex aggregation pheromone buds and flowers. Also look for 8°C and 35°C, but needs a relative The main thrips pest of protected specific to WFT is available from symptoms of thrips-transmitted • Conventional sticky traps or long humidity of at least 65% in the plant ornamental crops, WFT, is resistant • Adults of some thrips species can Syngenta Bioline. The pheromone viruses. ‘curtain’ traps can be useful to trap micro-climate for the eggs to survive. to many pesticides. Therefore the be recognised easily. For instance, is produced by WFT males and thrips adults in empty structures, Adult mites are oval, beige and about most effective control strategies are grain thrips are much darker than attracts both male and female • Use favourite host plants or between infested crops and new 0.4 mm long. They are wingless, so those used within an Integrated Pest other species. WFT for mating. The pheromone is or those particularly susceptible batches of plants. However, they are best applied to touching plants to Management (IPM) programme. IPM supplied as small rubber lures which to damage as ‘indicator plants’. can also catch flying biological allow them to walk from plant to plant. strategies include cultural, biological • WFT and onion thrips cannot be are stuck onto the lower section of For instance flowering verbena is control agents too so they should They are very active but are difficult to and chemical options, together positively identified by eye. sticky traps. These lures are also very attractive to WFT, while WFT be positioned and timed with care. find on ornamental plants as they are with regular monitoring.The strategies An entomologist can confirm the claimed to improve the efficacy of damage to petals shows up usually in the same hiding places as described here are particularly species using a microscope. abamectin (eg Dynamec) against on chrysanthemum varieties with • Maintain strict weed control inside the thrips larvae on which they feed. relevant to WFT and onion thrips and Traps can then be monitored by WFT, if used in the crop one hour dark pink, orange or red flowers. and around glasshouses or tunnels, A. cucumeris feeds only on young may not be as effective against other a member of staff trained in before pesticide application. This including any empty structures. Aim thrips larvae and not on the adults or species. If a quarantine thrips species thrips recognition. is thought to be due to the lures • Petunias can be used as indicator for a minimum of a 3 metre weed- pupae, so successful control depends is confirmed, Fera PHSI will issue a increasing the activity of WFT adults. plants for TSWV. Within a few free strip around the outside edges on a regular preventive introduction Notice outlining specific measures • Position traps over favourite host days of feeding by infected WFT, of structures. programme. The predators can to eradicate the pest and prevent it plants, imported plants and near • A thrips attractant for various thrips dark leaf spots develop. be sprinkled onto plants every week spreading to other nurseries. This will to doorways. species including WFT and onion • Do not take cuttings from infested in a bran or vermiculite carrier, or be designed in consultation with the thrips is available from Koppert. As • Pay attention to recently bought- mother plants. released from slow-release sachets grower and will include the required • Only use as many traps as can the attractant is not selective, it will in plants or cuttings, especially if hung onto plants, pots or baskets cultural, biological and/or chemical practically be checked every week not help to distinguish thrips species imported. • Remove any heavily infested plants (Figure 14). control methods, as appropriate for (eg one trap every 500 m2). More on traps. The attractant is supplied and any showing virus symptoms. the nursery concerned. (eg one per 100 m2) can be used in small slow-release dispensers that • If any thrips are suspected to be in smaller glasshouses or tunnels, are stuck onto sticky traps. a quarantine species, notify Fera • Thrips can be carried on staff or in high risk situations, or when PHSI immediately (see Further clothing. Staff should work in ‘clean’ Monitoring monitoring different crops in the Plant monitoring information section). glasshouses before known infested same glasshouse. • Do not rely on sticky traps alone areas in any one day. A regular monitoring programme, for monitoring thrips. Check designed to spot the first sign of • Position traps just above the Cultural control • Further information on nursery thrips and to detect any ‘hotspots’ or plants using canes, plant labels hygiene for ornamental crops and increase in population levels is critical or strings, and move them up as Prevention of thrips problems is on soil disinfestation options for for successful thrips management. plants grow. If using IPM, placie better than cure, and cultural control cut flower growers is provided in Both sticky traps and plants should the traps a foot above the plants methods (of which there are many) HDC Factsheets 10/07 ‘Guidelines be monitored throughout the year, to reduce the numbers of flying play an important role in thrips on nursery hygiene for outdoor and whenever susceptible crops or beneficial agents caught. management: protected ornamental crops’ and imported plant material is present. 09/07 ‘Soil disinfection options for • Check traps weekly and record • If a previous crop has been cut flower crops’. Sticky traps numbers of pest thrips species, infested, use a thorough clean- • Adult thrips are attracted to both making sure to replace them up programme to minimise yellow and blue sticky traps. Blue regularly. thrips carry-over to following Biological control traps can be more effective than crops. Promptly dispose of any yellow at detecting low densities Thrips lures crop debris, unmarketable plants, Several biological control agents are of WFT. However, yellow traps will Two lures are available, designed to weeds, used pots, trays and available for the control of thrips. 14 Typical Amblyseius cucumeris slow catch all thrips species and thrips increase sticky trap catches of thrips, 13 Western flower thrips female on trap old matting. Place into sealed Those used on protected ornamentals release sachet on a hanging basket Application can be done by hand, Steinernema feltiae nematodes are supplied in a end. The adults are very active and Once the fungus has colonised the control by luring thrips out of or using an automatic applicator These insect-pathogenic nematodes gel-like carrier in plastic trays, for can both run and fly, but often remain thrips body, it can be seen as white their hiding places and increasing such as the ‘Airbug’ supplied by were first developed as substrate application in water. It is critical hidden within the growing media and fluff on the body surface. Fungicides exposure to foliar applied pesticides Koppert (Figure 15). The slow–release drenches for the control of sciarid to follow all the product recommen- under pots or trays. The young larvae need to be chosen with care and when used as a tank mix. A sugar sachets only need to be used every fly larvae. However, they are now dations for effective results, such as are small and white and older larvae their application timed to cause least solution product (‘Attracker’) is 6–8 weeks, and are supplied as indi- also used successfully as foliar correct application rate and use-by are 3–4 mm long and brownish- harm to Mycotal; check the product available from Koppert. vidual sachets, or in strips (‘Bugline’, applications for WFT control, partic- date, removal of fine filters in the yellow. The beetles are supplied in label or contact the supplier. supplied by Syngenta Bioline – Figure ularly on chrysanthemums. The application equipment and continued tubs in a compost and vermiculite • An approved pesticide should 16) for use in (eg chrysan- nematodes kill the host insect by agitation of the spray tank during carrier. Research in HDC project PC Beauveria bassiana only be used if necessary, and the themums). The strips of sachets can releasing a bacteria from their gut application. 261 showed that Atheta reduced This fungus (Naturalis-L) has recently choice will depend on thrips species be applied using the sprayer gantry, once inside the thrips body. S. feltiae WFT numbers on impatiens through been approved in the UK for use present, history of pesticide effi- which saves labour and enables can kill WFT adults and larvae on the Atheta coriaria use of the grower ‘DIY’ rearing- on any protected edible or protected cacy on the nursery and whether or access to the crop. plants, but their main role in WFT This ground-dwelling predatory release system developed in HDC ornamental crop, for control of not IPM is being used. control is by killing the thrips larvae (rove) beetle is available for control project 239a. whitefly and thrips. B. bassiana works Amblyseius swirskii that drop to the ground to pupate, of sciarid and shore flies. Both the in a similar way to V. lecanii but is • It is very important to follow This predatory mite looks very and the pupal stages in the ground. adults and larvae will also eat other Insect-pathogenic fungi not so dependent on high humidities. pesticide label recommendations similar to A. cucumeris and feeds on Nematode applications should be prey in the growing media or soil, Insect-pathogenic fungi are micro- Infected thrips are covered with small carefully, including Resistance thrips larvae and also on whitefly made weekly, and as they do not give including thrips larvae and pupae. biological control agents and are balls of white fungus (Figure 17). Management Guidelines. Avoid eggs and young scales. A. swirskii a quick knock-down of thrips, they The adult beetle is about 3–4 mm therefore subject to the pesticide using the same chemical or is not native to the UK and only has should start at low WFT densities or long, dark brown and shiny, with approval system (unlike predators, chemical group repeatedly, as this a licence for release in fully enclosed used preventatively. The microscopic short wings and an upturned rear parasites and nematode biological Chemical control can select for pest resistance. glasshouses or tunnels. A. swirskii control agents). Two fungal products For example, although spinosad needs warmer temperatures than are approved in the UK that will give • Thrips are difficult to control with (Conserve) is currently the most A. cucumeris to develop and some control of thrips: pesticides. WFT is resistant to effective pesticide against WFT, establish in the crop; the minimum many pesticides, and UK pop- resistance has occurred in some temperature is 15ºC and optimum Verticillium lecanii ulations of onion thrips collected UK WFT populations (eg on temperatures are 25–28ºC, when The whitefly strain of this fungus from salad onion and leek crops chrysanthemum and strawberry it multiplies more rapidly than A. (‘Mycotal’) will also infect thrips. have recently been shown to be where Conserve and Tracer cucumeris. In bedding, pot and cut Mycotal has approval for use resistant to pyrethroids. respectively have been over-used). flower crops, a good strategy for on protected ornamentals, and is using Amblyseius species would be supplied as spores in a wettable • In addition, thrips are difficult • Table 1 overleaf lists pesticides that to use A. cucumeris at the recom- powder for application as a high targets as adults and larvae often are currently approved on pro- mended preventive rate in the early volume spray. To be effective, the hide under leaves or in buds or tected ornamentals that may give season, then if thrips numbers fungus needs at least 18°C and growing points, and most pupae some control of thrips, depending increase, use higher release rates or a relative humidity of more than 75% of WFT and onion thrips are on species and resistance status. switch to A. swirskii if temperatures for 10–12 hours after application. located in the growing medium or are suitable. It is therefore most suitable for substrate. use during warm, humid weather, Hypoaspis miles in propagation houses, or when • Sugar solutions have sometimes and Hypoaspis aculeifer rooting cuttings under polythene. been claimed to improve thrips These ground-dwelling predatory mites are primarily used against 15 The ‘Airbug’ automatic applicator from Koppert sciarid flies, but will also feed on other prey in the growing media, soil or on matting, including thrips pupae. They should not be relied upon as the sole method of thrips control, but could supplement control when used alongside other biological control agents such as Amblyseius spp. The adult mites are up to 0.8 mm long, off-white with a large pale brown shield on their backs. Hypoaspis spp. need moist growing media, soil or sub- strate and temperatures above 15ºC. They are supplied in tubs with a peat and vermiculite carrier for sprinkling on the floor or benches. The mites are very active and can often be seen running on the substrate 16 Amblyseius cucumeris can be released to cut flower crops from this ‘Bugline’ strip surface or under pots and trays. supplied by Syngenta Bioline 17 Thrips infected with Beauveria bassiana are covered with small balls of white fungus Table 1 Currently approved pesticides (May 2009) on protected ornamental plants that may give some control of thrips Pyrethrins Pyrethrum 5 EC Pyrethrins Label approval High Harmful to some Contact action. Spruzit volume bio-controls for up WFT and onion Active Product name Insecticide group Approval status Appli- Compatability with Comments spray to 1 week thrips likely to be ingredient (examples) for protected cation biological control resistant ornamentals method agents* Spinosad Conserve Spinosyn Label approval High Harmful to some Contact and Abamectin Acaramik Avermectin Label approval High Harmful to Contact and volume bio-controls ingestion action. Clayton Abba volume nematodes for up translaminar action spray (parasitic wasps) Usually effective Dynamec spray to 7 days and to for up to 1 week against WFT most other bio- but resistance controls for up to confirmed in some 3 weeks UK populations where over-use Beauveria Naturalis-L Entomopathogenic Label approval High Safe to some bio- UK label details has occurred bassiana fungus volume controls not yet available spray (May 2009) Teflubenzuron Nemolt Benzoylurea SOLA 2120/07 High Safe to most Contact and volume bio-controls ingestion action. Cypermethrin Sherpa 100 EC Pyrethroid Label approval High Safe to nematodes Contact action. spray Insect growth Toppel 100 EC volume Harmful to most WFT and onion regulator. SOLA spray other bio-controls thrips likely to be expires 31 Decenber for up to 12 weeks resistant 2013

Thiacloprid Agrovista – Neonicotinoid SOLA 0474/08 High Harmful to some Contact, Reggae SOLA 3728/06 volume bio-controls for translaminar and Deltamethrin Bandu Pyrethroid Label approval High Safe to nematodes Contact action. Calypso spray up to 2 weeks systemic action Cleancrop volume Harmful to most WFT and onion Decathlon spray other bio-controls thrips likely to be Thiamethoxam Centric Neonicotinoid SOLA 2230/08 High Harmful to some Contact, ingestion Decis for up to 12 weeks resistant volume bio-controls for and systemic action Decis Protech spray up to 2 weeks Pearl Micro Verticillium Mycotal Entomopathogenic Label approval High Safe to bio- Contact action Deltamethrin Bandu Pyrethroid SOLA 1611/07 Fog Safe to nematodes Contact action. lecanii fungus volume controls Cleancrop SOLA 1633/07 Harmful to most WFT and onion spray Decathlon SOLA 1693/07 other bio-controls thrips likely to be Decis SOLA 1650/07 for up to 12 weeks resistant Decis Protech • SOLA = Specific Off-label approval regulations. All pesticides formerly • If in doubt about which products permitted for use under the LTAEU are permissible on ornamentals Imidacloprid Intercept 70 WG Neonicotinoid Label approval Substrate Safe to nematodes Systemic action. • Growers must hold a paper or (allowing extrapolation of use from or how to use them correctly, drench Harmful to some Plants in containers electronic copy of a SOLA before a label approval or SOLA to use seek advice from a BASIS-qualified bio-controls for up only using any product under the on an ornamental crop) are in the consultant with expertise in orna- to 6 weeks SOLA arrangements. Any use of a process of being evaluated by the mental plant production. pesticide with a SOLA is at grower’s Chemicals Regulation Directorate Natural plant Eradicoat Physical pesticide Exempt from High Safe to bio-con- Contact action own risk. Relevant SOLAs are sent (CRD), formerly known as PSD. • Important – Growers must always extracts Majestik pesticide volume trols once spray to HDC members by HDC, or are Where possible, CRD has issued check the current approval status regulations spray deposit dry available from CRD (see below) new SOLAs to replace the LTAEU. of products listed in this factsheet or from consultants. However, some pesticides formerly before intended use as this Nicotine Nicotine 40% Alkaloid Label approval Smoke Harmful to some Fumigant action. permitted for use under the LTAEU could have changed since it was shreds bio-controls for up Poor control of • Always follow label or SOLA no longer meet the regulatory produced. to 3 days WFT likely. Approval recommendations, including rate requirements and these are not for use expires of use, and check the range permitted for use after 1 June 2009. *Full details of compatibility of 8 June 2010 of ornamentals listed which can Some pesticides have not yet been pesticides with biological control be safely treated. If crop safety processed by CRD and these can agents are available from biological Nicotine No-Fid Alkaloid Label approval High Harmful to some Contact and information is unavailable, test the continue to be used under the control suppliers or consultants. Stalwart volume bio-controls for up fumigant action. product on a small number of plants LTAEU at grower’s own risk after XL All Nicotine spray to 1 week Poor control of first before use on a larger scale. 1 June 2009, until they are pro- 95% WFT likely. Approval cessed further by CRD. Further, up for use expires • The Long Term Arrangements for to date information is available from 8 June 2010 Extension of Use (LTAEU) are being the CRD Information Service phased out from 1 June 2009, due (Tel. 01904 640500) or on the CRD Table continued... to EU harmonisation of pesticide website www.pesticides.gov.uk Further information The Old Brickyard Koppert UK Ltd Ashton Keynes Green House Other useful publications Swindon Hornefield Business Park Wilts SN6 6QR Hornefield Road • DCH Crop Walkers’ Guide, Tel. (01285) 860015 Haverhill Suffolk CB9 8PQ Pot and bedding plants. www.agralan.co.uk Tel. (01440) 704488 www.koppert.co.uk • HDC Factsheet 19/08: ‘Iris Yellow Becker Underwood UK Spot Virus: A potential threat to (insect-pathogenic nematodes) Syngenta Bioline the onion industry’. Unit 1 Telstar Nursery Harwood Industrial Estate Holland Road • HDC Factsheet 10/07: ‘Guidelines Harwood Road Little Clacton, Clacton on nursery hygiene for outdoor Littlehampton Essex CO16 9QG and protected ornamental crops’. West Sussex BN17 7AU Tel. (01255) 863215 Tel. (01903) 732323 www.syngenta-bioline.co.uk • HDC Factsheet 09/07: www.beckerunderwood.com ‘Soil disinfection options for Biocontrol agents and sticky traps cut flower crops’. BCP Certis can also be obtained through most Newbury House horticultural merchants. • HDC Project 261 Protected Court Lodge Farm bedding and pot plants: Evaluation Hinxhill, Ashford of western flower thrips control Kent TN25 5NR Useful contacts by Atheta coriaria using an Tel. (01233) 667080 on-nursery rearing system. www.bcpcertis.com Food and Environment Research Agency (Fera) – Incorporating the Plant • ADAS/Defra IPM in protected Biowise Health and Seeds Inspectorate (PHSI) ornamental crops, a best practice Hoyle Depot Sand Hutton York guide for UK growers (available Graffham, Petworth Yorkshire YO41 1LZ from ADAS UK Ltd, Boxworth, West Sussex GU28 0LR Tel. (01904) 465625 Cambridge, Tel. (01954) 256214). Tel. (01798) 867574 www.fera.defra.gov.uk/contactUs/ www.biowise-biocontrol.co.uk contactPlh.cfm

Suppliers of biological Fargro Ltd control agents Toddington Lane, Littlehampton West Sussex BN17 7PP Agralan Ltd Tel. (01903) 721591 (Biobest products) www.fargro.co.uk

Acknowledgements • Figures 6, 8 and 9 - copyright Fera

Thanks to Dominic Collins, Fera, • Figure 15 - copyright Koppert. for comments on thrips recognition features. • Figure 16 - copyright Marilyn Steiner. • Figures 1, 3, 7, 10, 11, 12, 13 and 14 - copyright ADAS. • Figure 17 - copyright Warwick HRI.

• Figures 2, 4 and 5 - copyright Nigel Cattlin/FLPA.

Whilst publications issued under the auspices © 2009 of the HDC are prepared from the best Agriculture and Horticulture Development Board. available information, neither the authors or No part of this publication may be reproduced in the HDC can accept any responsibility for any form or by any means without prior permis­ inaccuracy or liability for loss, damage or injury sion of the Horticultural Development Company. from the appli­cation of any concept or November 2009 procedure discussed. Design and production: HDR Visual Communication