Mite Management Strategy and Miticide Resistance

Frank ZalomDept. of Entomology

University of California, Davis

12th Annual Ventura County Strawberry Production MeetingCamarillo, September 5, 2013

Tetranychus urticaeTwo spotted spider mite

What’s up?

Two-spot mite: seasonal observations• Two-spotted mites live on a wide variety of

crops and weeds and can be carried from place to place by the wind - new strawberry plantings can be invaded early

• Mites develop slowly when conditions are cool (lower developmental temperature is 53.1oF)

• Populations build up during spring when temperatures start to increase

Susceptibility depends on• Variety• Plant vigor Chilling of day-neutral varieties Nursery fumigation Horticultural practices• Irrigation (water stress promotes mites)• Dust• Time of season and plant growth cycle

Two-spot mite feeding results in• Yield reduction (primarily fewer fruit, not fruit

size)• Greatest impact from early season mite feeding

- February to May (bud differentiation?)• Effect of early season feeding on yield

continues throughout the season

High mite densities appear as• Yellowing on upper leaf surfaces• Red to purple leaves at high densities often

beginning at leaf margins• Webbing

By the time these symptoms are observed, yield loss has already occurred

• Yellowing on upper leaf surfaces• Red to purple leaves at high densities often

beginning at leaf margins• Webbing

High mite densities appear as

Determine mites and predators per midtier leafletFall plantings - sample every other week starting when the first leaf is fully expanded, and begin weekly sampling when daytime temperatures reach 68° to 70°F consistently or when mites begin to increaseSecond year plantings - assume that mites ARE present; monitoring less important than treating early-season with ovicide or growth regulator to reduce overwintering mites

Monitoring

Presence/absence sampling - examine leaves in the field to see if mites are present; count percent of leave with mites NOT number of mites per leafThis method is fast for early season, but not accurate when densities exceed 10 per leaflet or following an acaricide spray

• Sample the oldest fully expanded leaves early in the season

• Later in the season, select mature leaves from the middle tier of the plant

Monitoring

Presence/absence sampling -

Number of leaflets infested in a 100 leaflet sample

Estimated number of active mites per leaflet

4 0 1 5 0 2 6 0 5 7 0 1 0 8 0 2 0

Monitoring

Sample at least 50 and preferably 100 midtier leaflets at random from each block of 5 to 10 acres

Midtier leaflet

What is a 'midtier leaflet'?

A mature leaflet from the middle tier of the plant - leaves that are dull green, not bright and shiny, but not old or dirty

Monitoring

Monitoring - mite brushing• Place 10 randomly

selected leaflets in individual bags and keep cool

• Brush leaflets onto glass plates in groups of 10

• Count under low power dissecting microscope

Glass plate with vegetable oil

• Early season - < 5 mites / midtier leaflet• Later season - 15 - 20 mites / midtier leaflet

Based on studies of 'Selva'Walsh, D. B., F. G. Zalom and D. V. Shaw. 1998. Interaction of the two spotted spider mite (Acari: Tetranychidae) with yield of day-neutral strawberries in California. J. Econ. Entomol. 91(3): 678-685

Thresholds

Validated on study of 'Diamante' in 2006

Diamante Treatment Timing, 2006

Diamante Treatment Timing, 2006

Mite-days (= total mites) are important

Diamante Treatment Timing, 2006

Early season mites are important

Varietal Susceptibility

Evaluated annually from 1989 to 2011with Dr. Doug Shaw

Selva

Variety and advanced selection evaluation, Watsonville, 2011

Variety and advanced selection evaluation, Watsonville, 2011

Mite suppression through first fruiting cycle makes a difference in yield

AcaricidesAcaricides

Two-spot mite - AcaricidesThe two-spotted spider mite has been reported to be resistant to over 92 unique insecticide or miticide active ingredients in over 367 cases worldwide.

This is among the most of any arthropod studied.

Two-spot mite - Acaricides• Older products like Omite, Vendex and Kelthane

had extended preharvest intervals or worker re-entry intervals that often dictated when they had to be applied

• Registrations for most of these were suspended during the 1990s

• Some (Kelthane) became ineffective due to resistance in some areasAcaricides became a critical problem when strawberry growers lost use of Omite as only Agri-mek was available - Goal was to register alternatives to Agri-Mek

• Newer products that have been registered represent an assortment of additional modes of action

Provide greater flexibility: shorter preharvest intervals some have fewer impacts on beneficials opportunity for resistance management

Two-spot mite - Acaricides

Resistance Management

• Spray only when necessary and treat only infested portions of the field.

• Avoid early-season insecticide applications that are disruptive to beneficial arthropods.

• Alternate acaricides that have different modes of action.

Principles -

Acaricide ClassificationAcaricide ClassificationProduct Active Ingredient Primary Target Site of Act ion IRAC # Kelthane Dicofol Unknown mode of act i on Unk. Vendex Fenbutatin oxide Oxidative phosphorylation inhibitor 12B Omit e Propargite Oxidative phosphorylation inhibitor 12C Agri-Mek Abamec t i n Chloride channel activato r 6 Savey Hexythiazox Unknown mode of action (mite growth regulator) 10A Z ea l Etoxazo le Unknown mode of action (mite growth regulator) 10B Acram i t e Bifenazat e Neuronal inhibitor (unknown mode of act ion) Unk. Oberon Spiromesi fen Inhibitor of lipid synthes i s 23 Kanemit e Acequinocy l Site III electron transport inhibitor 20B Fujimite Fenpyroximat e Site I electron transport inhibitor 21 Nealta 1 Cyflumetofen METI II electron transport inhibitor 25 Omni oil Mineral oil Highly refined mineral oil Uncl. Stylet o i l Mineral oil Highly refined mineral oil Uncl. GC Mite and others

Organic oils and extrac t s

Botanicals, exempt from tolerance Uncl.

1 Not registered for use on any crop in California

Two-spot mite resistance?• Dip strawberry leaves in different concentrations• Let leaves air dry• Transfer 10 to 15 adult female mites to the

leaves• Evaluate for mortality after 72 hours

Source of adult females are collections from strawberry fields. Population colonies are established on strawberry plants until sufficient adult females are available to conduct miticide bioassaysInitial locations:• Zalom susceptible colony (> 25 years without

treatment)• Irvine• Santa Maria (West Stowell Rd.)• Nipomo (Oso Flaco Lake Rd.)

Two-spot mite resistance?

Sampling site n Slope ± SE LC50 ppm LC90 ppm Zalom Lab Susceptible 329 5.528 (±0.899) 0.016 0.026 Santa Maria (Stowell Rd.) 658 1.259 (±0.117) 12.7 132.4 Nipomo (Oso Flaco Rd.) 291 1.604 (±0.189) 2.0 12.7 Irvine (Irvine Blvd.) 205 1.212 (±0.188) 2.4 27.7 Irvine (Irvine Blvd.) 334 1.564 (±0.163) 13.8 90.7 Oxnard (Central Ave.) 453 1.397 (±0.124) 11.7 96.3 Oxnard (Raytheon Rd.) 286 1.211 (±0.133) 2.7 31.0 Oxnard (E. Hueneme Rd.) 288 1.102 (±0.128) 5.9 86.2 Lewis mite (Foothill Rod.) 167 <0.0055 <0.0055

Agri-mek

Field rate -16 oz./acre in 200 gal. = 11.25 ppm

Two-spot mite resistance?

Two-spot mite resistance?Acramite

Field rate -1 lb./acre in 200 gal. = 300 ppm

Sampling site n Slope ± SE LC50 ppm LC90 ppm Zalom Lab Susceptible 240 3.072 (±0.418) 12.6 32.8 Santa Maria (Stowell Rd.) 770 2.112 (±0.165) 193.2 781.4 Nipomo (Oso Flaco Rd.) 372 1.861 (±0.187) 219.1 1070.1 Irvine (Irvine Blvd.) 428 1.474 (±0.153) 22.6 167.6 Irvine (Irvine Blvd.) 335 1.301 (±0.145) 5.9 56.6 Oxnard (Central Ave.) 664 0.998 (±0.084) 17.7 339.8 Oxnard (Raytheon Rd.) 574 1.473 (±0.123) 14.6 108.0 Oxnard (E. Hueneme Rd.) 285 1.508 (±0.208) 18.5 130.8 Lewis mite (Foothill Rd.) 378 1.784 (±0.189) 29.2 152.9

Two-spot mite lab resistance selection

• Established a field population• Challenged the field population with Agri-mek

or Acramite weekly at LD50 rate for 8 weeks

LC50 Agri-mek® LC50 Bifenture® LC50 Acramite®

Field colony

Two-spotted spider mite field population exposed to Agri-mek by lab selection at original LD50 value.

6 12 60 600 1201

Abamectin-exposed colony

LC 50 increased by 23X in 8 generations

PPM

Two-spotted spider mite field population exposed to Acramite by lab selection at original LD50 value.

Bifenazate-exposed colony

2 10.2 20.3 102

LC 50 increased by 4X in 8 generations

PPM

Acaricide compatibility -

Galendromus occidentalis

Phytoseiulus persimilis

Integrating Pesticides and Biocontrol of Mites

Predator bioassays -Contact and residual bioassaysUp to 37 days after applicationDirect and side effects of -

Saenz de Cabezon Irigaray, F. J., F. G. Zalom, and P. B. Thompson. 2007. Residual toxicity of acaricides to Galendromus occidentalis and Phytoseiulus persimilis reproductive potential. Biological Control. 40:153-159.

Acaramite = Bifenazate Agri-mek = Abamectin Kanemite = Acequinocyl Oberon = Spiromesifen Zeal = Etoxazole Fujimite = Fenpyroximate

Total effects (E) of acaricide residues on P. persimilis recorded 72 h after exposure to strawberry leaflets treated

with the labeled dose of formulated products.

IOBC categories: A = short lived (<5 d), B = slightly persistent (5-15 d), C = moderately persistent (16-30 d), D = persistent (>30 d)

Days after treatmen t Treatmen t 3 6 1 0 1 4 1 7 2 4 3 0 3 7

IOBC

Bifenazate 10 0 5 4 6 1 2 9 2 6 0 0 0 B Etoxazol e 10 0 1 00 10 0 1 00 10 0 1 0 0 1 0 0 10 0 D Spiromesife n 10 0 1 00 9 9 0 1 2 0 0 0 B Abamectin 10 0 7 0 5 9 1 9 3 2 1 2 B Fenpyroxima te 10 0 1 00 10 0 1 00 10 0 1 0 0 1 0 0 10 0 D Acequinocyl 10 0 5 6 0 0 0 0 0 A

Eotetranychus lewisiLewis mite

Tetranychus urticae

Eotetranychus lewisi

Average percent mortality of adult female Lewis mites exposed to registered acaricides in a laboratory bioassay

Mite Management Strategy and Miticide Resistance

Frank ZalomDept. of Entomology

University of California, Davis

12th Annual Ventura County Strawberry Production MeetingCamarillo, September 5, 2013