Spider mite resistance management strategy

European red mite eggs
on the calyx of an apple.
(Photo: www.hortnet.co.nz)

R.B. Chapman and N.A. Martin

(Revised T.J.B. Herman Feb 25)

Reasons for strategy and update

Spider mites are well known for their capacity to develop resistance to many classes of insecticide and miticide. Due to the inherent variation among spider mite populations, it is difficult to generalise about resistance development, cross-resistance patterns and other aspects related to miticide resistance. Resistance management strategies for spider mites may delay the onset of resistance or suggest alternative management approaches when resistance has developed. However, expert assistance should always be sought when resistance problems arise. Pest management strategies aimed at preventing or minimising resistance will help maintain control and conserve the effectiveness of existing products. This is an update of earlier resistance management strategies (Insecticide and Miticide Resistance Task Group, 1996 and Chapman and Martin 2004).

Background

Spider mites are a group of plant feeding mites that belong to the family Tetranychidae. Some species can be severe pests on fruit trees, greenhouse vegetable and flower crops. Outbreaks of mites are often associated with the use of pesticides used to kill insects, but which also kill the mites' natural enemies.

In New Zealand, the most common spider mite pests belong to two genera, Panonychus and Tetranychus. Panonychus species produce little webbing, while Tetranychus species often produce much webbing. The species are difficult to distinguish morphologically. The presence of T. cinnabarinus in New Zealand requires confirmation (Zhang 2002). T. evansi was found at eight sites in Auckland in 2020 (Fan et al. 2022) and was too widespread to consider a biosecurity response to prevent its spread. It is likely to have spread further within New Zealand.

The life cycle of all species comprises an egg stage, larval stage, two nymphal stages and adult. Most miticides kill only the active stages (larva, nymphs and adult mites). However, the relative effectiveness of miticides against immature and adult stages differs between miticides. Some miticides kill only the egg stage or have ovi-larvicidal action.

**Table 1:** Spider mite pest species in New Zealand.
Species	Common name
Eotetranychus seximaculatus	six-spotted mite
Panonychus citri	citrus red mite (CRM)
Panonychus ulmi	European red mite (ERM)
Tetranychus cinnabarinus¹	carmine spider mite
Tetranychus lambi	banana mite
Tetranychus ludeni	bean mite
Tetranychus urticae	two-spotted spider mite (TSM)

¹The presence of this species in New Zealand requires confirmation.

NB: Blister, bud, erineum, gall, and rust mites (eriophyids, family Eriophyidae) are not included here.

Products with label claims for spider mite control in New Zealand

Products with label claims for control of spider mites can be divided into three broad groups: mineral oils, insecticides (mainly organophosphates) and specific miticides. Many products that previously had label claims may no longer be effective. Products currently available in New Zealand that have label claims for miticidal activity are listed in Table 2.

**Table 2:** Products with label claims for whitefly control in New Zealand (February 2025)
Active ingredient(s)	Registered for	Crops registered for use
Beneficial insects
Phytoseiulus persimilis	TSM	Greenhouse, vegetable and ornamental crops and nurseries
Orius vicinus	TSM (thrips primary prey)	Greenhouse crops
IRAC insecticide mode of action group
3A Pyrethroids & pyrethrins
tau-fluvalinate	REM, TSM	Ornamentals
6 Avermectins & milbemycins
abamectin	ERM, TSM, six-spotted mite, tomato rust mite	Apples, avocadoes, ornamentals, pears, strawberries
Milbemectin	ERM, TSM, CRM, six-spotted mite	Apples, avocadoes, citrus, ornamentals, pears, stone fruit, strawberries
10A Clofentezine, Diflovidazin, Hexythiazox
clofentezine	ERM, TSM, CRM	Pipfruit, berry fruit, citrus, stone fruit, grapes (glasshouse), hops
10 B Etoxazole
Etoxazole	ERM, TSM, six-spotted mite	Avocadoes, pipfruit, black currants
12 C Propargite
Propargite	ERM, TSM, CRM	Apples, berry fruit, citrus, grapes, hops, stone fruit
21 A METI acaricides and insecticides
Fenpyroximate	ERM, TSM	Pipfruit

Current status of spider mite resistance in New Zealand

European red mite (ERM) was found to be resistant to organotin miticides (no longer registered) at some locations in New Zealand (Bowie et al. 1988). While at some locations both ERM and two-spotted spider mite (TSM) were resistant to propargite (Bowie et al. 1988; Chapman & Penman 1984; Kabir et al. 1991; Kabir et al. 1993).

While resistance to specific miticides is not thought to be widespread in New Zealand, excessive repeated applications (more than 3 applications per crop, per 12-month period or more than one application per season for ovicides and fenpyroximate) of miticides could lead to resistant populations becoming more prevalent.

Ovicide resistant TSM occur in Australia (Edge et al. 1987) and USA (Reissig & Hull 1991).

Resistance to tau-fluvalinate and mineral oils has not been detected in New Zealand.

Citrus red mite (CRM) resistant to the ovicide hexythiazox has been found at single sites in New Zealand, and miticide resistance for this species has also been found overseas (Cranham & Helle 1985). Note that hexythiazox is longer registered, but cross-resistance to clofentezine is known elsewhere (Herron, 1994).

Although spider mite resistance to newer miticide classes, e.g. mitochondrial electron transport inhibitors (METI) (e.g. fenypyroximate) and chloride channel activators (e.g. avermectin, emamectin) is not known in New Zealand, resistance to miticides in these groups is known overseas (e.g. Beers et al. 1998; Devine et al. 2001; Naeun et al. 2001).

Cross-resistance between miticide groups is also known. For example, an Australian TSM strain highly resistant to hexythiazox (no longer registered) and clofentezine was more tolerant of fenpyroximate and pyridaben (not registered in NZ) than a susceptible strain (Naeun et al. 2001).

Abamectin has been used widely by greenhouse flower growers to control TSM. Some growers have reported loss of control with this product. Resistance to this product by TSM is known overseas (Beers et al. 1998).

Resistance management and prevention strategy

Guidelines to reduce the risk of miticide resistance include the following:

Adopt or continue use of integrated fruit production (IFP), integrated mite control (IMC) or integrated pest management (IPM) programmes using predators.
Ensure that any pesticides used in pest and disease control programmes are safe to predators.
Avoid excessive repeated applications of miticides.
- hexythiazox - Must not be applied more than once per crop, per 12 month period.
- fenpyroximate - Must not be applied more than once per crop, per 12 month period.
- abamectin or milbemectin -
  PIPFRUIT Must not be applied more than once per crop, per 12 month period.
  OTHER CROPS Do not make more than 3 applications per crop, per 12 month period.
- dicofol or bromopropylate - Do not make more than 3 applications per crop, per 12 month period.
- Other miticides - Do not make more than 3 applications per crop, per 12 month period.
If more than one mite species needs to be controlled the total number of applications from each group of miticides should not exceed the limits described above.
If more than two applications are required, use miticides from different chemical groups, including oils where appropriate. Refer to Table 2 for miticides and their chemical groups. Note that cross-resistance can occur between some chemical groups, therefore, seek expert advice before making applications.
Ensure that miticide applications are correctly timed and that spray coverage is thorough, including the underside of leaves.

Note: Control failure does not always imply resistance.

Implementation

The following recommendations are made:

Miticide labels should carry the following statement:
IMPORTANT - RESISTANCE MANAGEMENT
Resistance to this pesticide could develop from excessive use. To minimise this risk, use strictly in accordance with label instructions. Avoid using this pesticide exclusively all season, and avoid unnecessary spraying. Maintain good cultural and biological control practices.
This resistance management strategy should be included:
i. in industry-wide spray programmes for export horticultural crops.
ii. on product labels for all miticides.
Where clofentezine has been used regularly over the past few seasons, advice should be sought from a specialist advisor. If the performance of this miticide is suspect at a site where there has been repeated use in the past, then this miticide should not be used again and products from a different chemical group introduced. Clofentezine resistance may confer cross-resistance to some miticides from other groups.

Crop recommendations

The following options are available for the design of spray programmes.

Note: All products listed may not be suitable for crops being exported to certain markets. Check with your export agency before applying any pesticide on export crops. Observe withholding periods.

Pipfruit: apples, pears and nashi.
An integrated fruit production (IFP) programme is available for apples using Typhlodromus pyri and Phytoseiulus persimilis. Miticide applications should be based on monitoring and spray thresholds as set out in the NZ Apple & Pear IFP manual

Summerfruit (Stonefruit)
An integrated mite control programme is available for apples using Typhlodromus pyri and Phytoseiulus persimilis.

Green tip: either clofentezine or mineral oil.
Petal fall onwards: either azocyclotin, or bromopropylate, or dicofol, or fenbutatin oxide, or propargite.
All-purpose spraying oil can be used throughout the summer at 1% except on russet-prone varieties.
Ensure thorough coverage and avoid excessive repeated applications (no more than one (of clofentezine) or three (of azocyclotin, bromopropylate, dicofol, fenbutatin oxide, propargite) spray(s) per crop, per 12 month period).

Strawberry

Runner beds: introduce Phytoseiulus persimilis.
Production beds: introduce P. persimilis..
If predators are not present in adequate numbers, or after planting and prebloom, apply miticides according to label instructions. Use either abamectin, or dicofol, or propargite, or clofentezine (prebloom only).
Ensure thorough coverage and avoid excessive repeated applications (no more than one (of clofentezine or three (of abamectin, dicofol, propargite) spray(s) per crop, per 12 month period).

Other berryfruit

Check labels as not all products have label claims for all crops.

Use either clofentezine, or propargite.
Ensure thorough coverage and avoid excessive repeated applications (no more than one clofentezine or no more than three propargite spray(s) per crop, per 12-month period).

Grapes

Use either clofentezine, or propargite.
Ensure thorough coverage and avoid excessive repeated applications (no more than one clofentezine and no more than three propargite spray(s) per crop, per 12-month period).

Hops

Use either clofentezine or propargite.
Ensure thorough coverage and avoid excessive repeated applications (no more than one clofentezine and no more than three propargite spray(s) per crop, per 12-month period).

Ornamentals

Integrated pest management (IPM) programmes using P. persimilis are available for some flower crops.

If predators cannot be used apply miticides according to label instructions. Use either abamectin, or tau-fluvalinate.
Ensure thorough coverage and avoid excessive repeated applications (no more than three sprays per crop, per 12-month period).

Glasshouse vegetable crops

Integrated pest management programmes using P. persimilis are available for most vegetable crops.

Use abamectin.
Ensure thorough coverage and avoid excessive repeated application (no more than three sprays per crop, per 12-month period).

References

Beers EH, Riedhl H, Dunley JE 1998. Resistance to abamectin and reversion to susceptibility to fenbutatin oxide in spider mite (Acari: Tetranychicae) populations in the Pacific Northwest. Journal of Economic Entomology 91: 352-360.

Bowie MH, Chapman RB, Walker JTS 1988. Monitoring azocyclotin and propargite resistance in European red mite. Proceedings of the 41st New Zealand Weed and Pest Control Conference: 189-192.

Chapman RB, Penman DR 1984. Resistance to propargite by European red mite and two-spotted mite. New Zealand Journal of Agricultural Research 27: 103-105.

Chapman RB, Penman DR, Walker JTS 1987. European red mite resistance to organotin miticides in Hawkes Bay apple orchards. Proceedings of the 40th New Zealand Weed and Pest Control Conference: 94-98.

Devine GJ, Barber M, Denholm I 2001. Incidence and inheritance of resistance to METI-acaricides in European strains of two-spotted spider mite (Tetranychus urticae)(Acari: Tetranychidae). Pest Management Science 57: 443-448.

Edge VE, Rophail J, James DG 1987. Acaricide resistance in two-spotted mite, Tetranychus urticae in Australian horticultural crops. In: Thwaite WG ed. Proceedings of the Symposium on Mite Control in Horticultural Crops, Orange, NSW, Australia. Pp. 87-91.

Fan Q-H, Dongmei L, Sherly G 2022 Response to an incursion of tomato red spider mite Tetranychus evansi in New Zealand. Zoosympoisa 22:71

Herron GA 1994 Clofentezine-hexythiazox resistance in two-spotted mite Tetranychus urticae Koch (Acari: Tetranychidae) in Australia. PhD Thesis, University of Sydney

Insecticide and Miticide Resistance Task Group 1996. Spider Mite Resistance management Strategy. In: Bourdot GW, Suckling DM ed. Pesticide Resistance: Prevention and Management. New Zealand Plant Protection Society, Lincoln, New Zealand. Pp. 177-183.

Kabir KH, Chapman RB, Penman DR 1991. Use of a discriminating concentration form monitoring propargite resistance in twospotted spider mite. Proceedings of the 44th New Zealand Weed and Pest Control Conference: 252-256.

Kabir KH, Chapman RB, Penman DR 1993. Monitoring propargite resistance in European red mite Panonychus ulmi (Acari: Tetranychidae). New Zealand Journal of Crop and Horticultural Science 21: 133-138.

Reissig HW, Hull LA 1991. Hexathiazox resistance in a field population of European red mite (Acari: Tetranychidae) on apples. Journal of Economic Entomology 84: 727-735.

Zhang Z-Q 2002. Taxonomy of Tetranychus ludeni (Acari: Tetranychidae) in New Zealand and its ecology on Sechium edule. New Zealand Entomologist 25: 27-34.