Thrips insecticide resistance management and prevention strategy

Western flower thrips damage
Western flower thrips damage on English daisy
(Photo: Whitney Cranshaw, Colorado State University,

N.A. Martin
Crop and Food Research, Private Bag 92 169, Auckland, New Zealand

(Revised February 2005)

Reasons for strategy and update

Several species of thrips (Thysanoptera) including two economically important species, onion thrips and western flower thrips, that are present in New Zealand, have become resistant to pesticides. Pest management strategies aimed at reducing or preventing resistance will help conserve existing products for ongoing effective use. This is an update of the earlier resistance management strategy (Martin 1996).


A wide variety of thrips, mainly exotic, but also including indigenous species, can cause unacceptable damage to plants. In addition, the presence of thrips, especially indigenous species, on export produce can cause consignments to be rejected or treated for reasons of quarantine security imposed by importing countries.

The eggs and pupae of thrips are usually protected from insecticide sprays (see below). This, together with their rapid development at higher temperatures, makes them particularly difficult to control with insecticides and often results in frequent applications or use of persistent insecticides.

Thrips species and strains

Thrips (Thysanoptera) are grouped into two suborders, Terebrantia and Tubulifera, with most pests in the Terebrantia.


A large number of minor pests and a few important pests in this group belong to the family Thripidae. Plants from most families may be attacked by these thrips, especially when grown in a greenhouse. The most important species in New Zealand are described below.


Products with label claims for thrips control in New Zealand

Some insecticides have label claims specifically for "thrips" control, but only two products claim control for particular species of thrips. However, some label claims are restricted to crops that have a distinctive complex of thrips species. Claims for thrips control on one crop with a particular pest complex may not be relevant to another crop with a different thrips pest complex. One chemical, methamidophos, which gives effective control of the pesticide-resistant greenhouse strain of western flower thrips, has no label claim for thrips control. Pesticides with label claims for thrips control are listed in Table 1. A biological control agent is also available for greenhouse crops.

In addition several oils claim to enhance insecticide efficacy. UK research shows that the addition of oils improves the spreading and therefore the chance of contact with sessile stages. The products with insecticide enhancement label claims for fruit and/or vegetables in New Zealand are Agpro Crop Oil, C-Dax Oil, Codacide Oil, D-C-Trate, Hasten, Rapid Plus and Spray-Sure Kwickin.

Additives such as oils, spreaders and stickers should only be used if the pesticide product label recommends the use of a spreader/sticker.

Table 1: Products with label claims for control of thrips in New Zealand (September 2002). Not all products listed for each pesticide may have a label claim for all crops indicated.
 Type of label claim for each crop group1
Pesticide category
and IRAC chemical group

Pesticide common and (product) names
Berryfruit Citrus Stonefruit/summerfruit Other fruit Onions Vegetables except onions Ornamentals and forestry
Biological control
Amblyseius cucumeris (Mite-A, Thripex)           T in GH T in GH
Hypoaspis aculifera (Entomite, Hypo-Mite)           SF in GH SF in GH
Mineral oils
mineral oil (Caltex, D-C Tron)   T          
Carbamates 1A
carbaryl (Carbaryl, Sevin) T   T T      
Organo-phosphates 1B
acephate (Lancer, Orthene)   XX          
azinphos-methyl (No longer registered)   T          
chlorpyriphos (Chlorpyriphos, Lorsban, Pychlorex)   T T T in GR      
diazinon (Basudin, Dew, Diazinon, Diazinyl, Gesapon)       T T T T
dichlorvos (Nuvos)         T T T
dimethoate (Dimezyl, Rogor)   T T T      
maldison (Malathion, Yates Maldison)   T T T     T
methamidophos (Metafort)         T    
Cyclodiene 2A
endosulfan (no longer registered)         OT T  
Fiprols 2B
fipronil (Ascend)   KCT          
Pyrethroids 3
alpha-cypermethrin (Bestseller, Dominex)         T    
cyfluthrin (Baythroid)         T    
deltamethrin (Decis, Deltaphar)         T    
lambda-cyhalothrin (Karate Zeon)       T OT    
tau-fluvalinate (Mavrik)     T T T   T
tau-fluvalinate + fungicide (Guardall, Supershield)             T
Pyrethrins 3
pyrethrum (Garlic & Pyrethrum)   T T T     T
Chloronicotinyls 4A
imidacloprid (Confidor)           T  

1T = thrips, OT = onion thrips, KCT = Kelly's citrus thrips, SF = sciarid fly, GH = greenhouse crops, GR = grapes, XX = label claim for control of aphids, leaf rollers and mealy bugs in citrus.

Current status of thrips resistance in New Zealand

Some thrips species present in New Zealand are major pests overseas, but of little consequence locally. The pesticide resistance status of these species has not been investigated.

Resistance management and prevention strategy

Thrips have life stages that are resistant to pesticides. For this reason a single application of a pesticide is rarely very effective. A brief understanding of thrips life cycle will help improve control of the pest.

Most pest thrips in New Zealand belong to the family Thripidae, whose life cycle will be described first. The winged adults (male and females) are mainly found on flowers and the youngest leaves. The females insert eggs into plant tissue, usually flowers or leaves. There are two larval stages which tend to occur where they can hide, e.g. between leaves or flower petals. There are two "pupal" stages, which are usually off the plant in the soil or litter. The adults hatch from the last pupal stage and fly back onto a plant. The egg and pupal stages are protected from pesticides and single applications of most pesticides will not kill these stages. Individuals may emerge from these stages when pesticide residues will no longer kill them.

The greenhouse thrips has a similar life cycle, except that the "pupal" stages remain on the leaves and all stages tend to be on old leaves. Similarly all stages of the bottlebrush thrips stay on the plant, but are protected in curled up leaves. The life cycles of the clover and lily thrips have significant differences, but the principles described for Thripidae apply.

Note: Control failure does not always imply resistance.

In New Zealand, the risk of pesticide resistance appears to be confined to onion thrips and western flower thrips, though possibly also Kelly's citrus thrips.


Guidelines to reduce the risk of the development of resistance to pesticides by gladiolus thrips, Kelly's citrus thrips, onion thrips, western flower thrips and to manage resistance to pesticides include:

Guidelines to reduce the risk of resistance development by greenhouse thrips include:

Crop specific recommendations

Crop specific IPM manuals which include pesticide resistance management and prevention strategies for thrips and other insects, mites and diseases, are available for greenhouse beans, capsicums, cucumbers, cymbidium orchids, roses and tomatoes.

Information on the life cycle of thrips and non-pesticide and pesticide controls for thrips grown in greenhouse or under protection is found in Crop & Food Research Broadsheets Nos 35 & 36.

Greenhouse crops

The strategies for greenhouse crops depend on whether the crop is one where pesticide residues are of concern (e.g. fruit and vegetables) or not.

The strategies in general are the same for all thrips infesting fruit and vegetable crops, but the selection of pesticides is severely limited where western flower thrips is present.

Crops that are susceptible to tomato spotted wilt virus have a lower tolerance of the two thrips vectors, onion thrips and western flower thrips.

Greenhouse vegetable and fruit crops - western flower thrips and other thrips

Biological control is practical for some greenhouse vegetable crops in New Zealand. It has been tested on capsicums and cucumbers, but may be suitable for other crops. Contact the suppliers of Amblyseius cucumeris for details on how to use and integrate the predator with control of other pests and diseases and for information on biological control of other pests. Incorporate non-pesticide methods of pest control suitable for the crop. IPM Manuals are available from Crop & Food Research for beans, capsicums, cucumbers and tomatoes. These programmes can also be adapted for zucchinis, eggplant, melons and pepinos.

If biological control is not practical or appropriate the following procedures should be incorporated into the crop protection programme:

See Table 1 for a list of insecticides registered for thrips control in each crop.

Greenhouse flower crops - western flower thrips and other thrips

The only IPM manuals for a flower crop with thrips as a pest are greenhouse roses and cymbidium orchids.

Biological control could also be suitable for crops such as chrysanthemums produced for the local market.

The strategy is as above for greenhouse fruit and vegetables, but without biological control.

See Table 1 for a list of pesticides registered for thrips control in each crop.

Outdoor flower crops

For transplants grown from seed or cuttings, take all the precautions listed.

Onion crops - onion thrips

Follow the onion thrips management strategy for onion crops published by the New Zealand Onion Exporters Association

See Table 1 for a list of pesticides registered for thrips control in onion crops.

Summer fruit and stone fruit - New Zealand flower thrips

New Zealand flower thrips can infest stone fruit flowers and ripening fruit. Nectarine flowers and fruitlets require protection, as do fruit of all export summer fruit at harvest time, and peaches and nectarines for local market. New Zealand flower thrips usually invade the crop from sources outside the orchard and the risk of pesticide resistance developing is low.

See Table 1 for a list of pesticides registered for thrips control in each crop.

Ornamentals/pot plants/pine nurseries - western flower thrips, greenhouse thrips and other thrips

The strategies in general are the same for all thrips infesting these crops but the selection of pesticides is severely limited where western flower thrips is present.

Crops that are susceptible to tomato spotted wilt virus have a lower tolerance of the vectors, onion thrips and western flower thrips.

For plants grown from seed or cuttings, follow the precautions listed above. However, if continuous batches of cuttings or seeds are planted, it is most useful to organise the propagation and production units to minimise transmission of thrips from one area to another. It is also important to keep mother plants from which cuttings are taken isolated and free from both thrips and virus by non-pesticide means.

See above for greenhouse fruit and vegetable crops.

See Table 1 for a list of pesticides registered for thrips control in each crop.

Note: see above with regards to western flower thrips.

Citrus and other fruit crops - Kelly's citrus thrips and greenhouse thrips

Kelly's citrus thrips damages young fruit and pupates in the ground, whereas greenhouse thrips damages mature leaves and older fruit, especially where fruit touch or fruit touch leaves, and pupates on the tree. Descriptions of life cycle and control options for citrus are in Mooney (2001).

For Kelly's citrus thrips see guidelines in "General Strategies" above. Start monitoring crops during flowering and continue until the fruit are safe from damage. Apply the first of a cluster of sprays when larvae are seen. If more than one cluster of insecticide sprays is required, use a product with a different active chemical.

For greenhouse thrips, see guidelines in "General Strategies" above.

See Table 1 for a list of pesticides registered for thrips control in each crop.

Berryfruit and other fruit crops not listed above.

Damage can occur from thrips feeding at flowering or on young fruit. Thrips presence on fruit for export can cause consignments to be declined or treated.

See Table 1 for a list of pesticides registered for thrips control in each crop. Note: see above with regards to western flower thrips and intonsa flower thrips.


Thanks for help from P. Stevens and G. McLaren, HortResarch.


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