Sugar beet conference 2017:

mites and caterpillars

Erik J. Wenninger

University of Idaho

Kimberly R & E Center

• Two-spotted spider mite • Caterpillars

Two-spotted spider mite – Damage

• Stippling and bronzing of leaves reduces

photosynthesis

TSSM - Identification

• Tiny specks on leaf

• Green, pink, red, cream, or yellow

• 2 black spots on the body

• Webbing on foliage

TSSM – Lifecycle

Overwinter in cracks in soil, leaf

litter, under loose tree bark

• WIDE host range

– Sugar beet, dry beans, alfalfa,

corn; weeds; ornamentals

Integrated Pest Management

•Cultural Control

•Biological Control

•Chemical Control

Integrated Pest Management

•Cultural Control

•Biological Control

•Chemical Control

Cultural Control

• Keep fields, field margins, and waste areas

free of weed hosts

Field bindweedCommon lambsquarters

Cultural Control

•Optimal irrigation

–Draught-stressed plants more susceptible to

spider mites

•Optimal fertilization

–Excess N fertilization flares spider mites

Cultural Control

• Sprinkler irrigation reduces dust deposits that

accumulate on plant leaves

Getty images

ipm.ucdavis.edu

Predatory mite

http://www.420magazine.com/gallery/data/500/galendromus_Lg.jpg

Integrated Pest Management

•Cultural Control

•Biological Control

•Chemical Control

Biological Control

Green lacewing

Lady beetlesipm.ucdavis.edu

Big-eyed bug

Minute pirate bug

Predatory mite

Predatory mite:

• flattened,

pear-shaped

• lacking spots /

coloration

http://www.420magazine.com/gallery/data/500/galendromus_Lg.jpg

Biological Control

•Promote natural enemies by:

1. Reducing dust deposits on foliage

2. Avoiding unnecessary insecticide /

miticide sprays

– Organophosphates (e.g., Lorsban) and pyrethroids

(Mustang, Asana) kill beneficials

Integrated Pest Management

•Cultural Control

•Biological Control

•Chemical Control

= organophosphate= “soft” chemistry

Common Name Trade Name PHI

Beauveria bassiana BotaniGard, Mycotrol —

azadiractin Aza-Direct, DeBug Trés —

azadiractin + pyrethrins Azera —

chlorpyrifos Lorsban and many others 30 days

garlic oil Garlic Barrier AG+ —

hexythiazox Onager 45 days

horticultural / mineral oil BioCover, JMS Stylet Oil, others —

naled Dibrom 2 days

oxydemeton-methyl MSR Spray Concentrate 30 days

phorate Thimet 30 days

potassium salts of fatty acids Des-X, Kopa, M-Pede —

potassium silicate Sil-Matrix, Carbon Defense —

sulfur (various) —

Treatment Rate% mortality

after 24 h

Check — 0.0 b

Onager 10 fl oz / a 0.0 b

Onager 14 fl oz / a 29.2 b

Onager 18 fl oz / a 72.2 a

Lorsban 0.67 pint / a 15.0 b

LSD 32.6

F 7.1

P 0.0005

Spider mite Petri dish trial

Onager label = 12-24 fl oz / a

Pyrethroids* Flare Spider Mites

• Lethal and repellant to predatory mites

• Repellant

– Disperse and become more uniform

– Reduced competition increases populations

• Shortened development time

• Female-biased sex ratio

*Pyrethroids = Mustang and Asana

TSSM – Monitoring

• Inspect leaves for bronzing and webbing

• Factors that increase risk:

– Hot, dry, dusty conditions

– Surface irrigation

– Field edges

Possible Sources of Spider Mites

• Corn fields

• Harvested alfalfa fields

• Drying bean fields

• Ditch banks

• Weedy areas (field bindweed / lambsquarters)

• Field edges with heavy dust

Border sprays (50 to 100 ft)

may be effective

Thresholds?

• No formal thresholds

• University of California recommendations:

– Mature beets can tolerate dozens to 100s of mites per

leaf without yield effects

– Early / mid-season infestation more damaging

– Spray if numbers increase over time and injury becomes

severe

– Consider weather forecast

• Two-spotted spider mite • Caterpillars

•Loopers

•Cutworms

•Armyworms

•Webworms

•“Others”

Sugar beet caterpillars

4 pairs prolegs

1-2 pairs prolegs

• Larvae feed on foliage

• Up to 1.5” long

• Green with thin white stripe

along each side

• 2 pairs abdominal prolegs

• Crawl in a characteristic

looping motion

http://www2.ca.uky.edu/entomology/entfacts/ef300.asp

http://mint.ippc.orst.edu/loopercycle.htm

Cabbage looper

Alfalfa looper

Loopers

•Loopers

•Cutworms

•Armyworms

•Webworms

•“Others”

Sugar beet caterpillars

4 pairs prolegs

1-2 pairs prolegs

Cutworms

• Larvae typically in soil

during day

• Usually feed at night

• Cut stem at or below surface

Army cutworm

Variegated

cutworm

Pale western cutworm

Harveson et al. 2009

Harveson et al. 2009 Harveson et al. 2009 Harveson et al. 2009

Armyworms

• Related to cutworms, but

brightly colored and feed

during day

• Skeletonize leaves

• “March” from field to field

Beet armyworm Western yellowstriped

armyworm

Bertha armyworm http://mint.ippc.orst.edu/berthalarva_lg.htm

Harveson et al. 2009 Harveson et al. 2009

•Loopers

•Cutworms

•Armyworms

•Webworms

•“Others”

Sugar beet caterpillars

4 pairs prolegs

1-2 pairs prolegs

Webworms• 3 sugar beet-feeding species

• Black dots on body

• Dark and light stripes running

length of body

• “Window” feeding, then

skeletonizationGarden webworm

http://extension.missouri.edu/p/ipm1019-18

Alfalfa webworm

www.ent.iastate.edu/imagegal/lepidoptera/alfwebworm/alfalfa_webworm.html

Harveson et al. 2009Beet webworm

•Loopers

•Cutworms

•Armyworms

•Webworms

•“Others”

Sugar beet caterpillars

4 pairs prolegs

1-2 pairs prolegs

False celery leaftierWoolybear /

Saltmarsh caterpillar

SB crown borerhttp://www.cals.uidaho.edu/edcomm/keys/plates/plate81.htm

Other caterpillars

in sugar beet