2014 Tri River Area

Pest Management Workshop

101 Ag Insects

1

Responding to Rootworm

Trait Failures

Frank B. Peairs

Colorado State University

(970) 491-5945

Frank.Peairs@Colostate.Edu

WESTERN CORN ROOTWORM

ROOTWORM FIELD BIOLOGY

EGGS: In soil from August to May

LARVAE: Feed on corn roots during June

and early July

PUPAE: In soil during July

ADULTS: Emerge in July and August. Feed

on corn and other plants. Lay eggs in corn

until frost.

WESTERN CORN ROOTWORM DAMAGE

AVERAGE GRAIN YIELD LOSS*

TO WESTERN CORN ROOTWORM

• Loss of 1 node = 18% yield loss

• Affected by location, weather,

year

*Excludes lodging losses

TOXIN EVENT TRADENAME

Cry34Ab1/Cry35Ab1 DAS 59122-7 Herculex RW

Cry3Bb1 MON 863 YieldGard Corn Rootworm

Cry3Bb1 MON88017 YieldGard VT

mCry3Aa MIR 604 Agrisure RW

eCry3.1Ab 5907 Agrisure Duracade

Bt Toxins - Rootworm

2014 Tri River Area

Pest Management Workshop

101 Ag Insects

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Multiple Toxins:

Agrisure 3122, AcreMax XTreme,

SmartStax

• 2-3 lep toxins

• 2 rootworm toxins

• LibertyLink

• glyphosate tolerant

• RIB and 5% refuges

RIB

Structured Refuge

Modified from Zhao et al. Nature Biotechnology 21: 1493.

RIB Strategy

♂(S) -> ♀(S) -> ♂(R) -> ♀(R)

A D U L T R O O T W O R M E M E R G E N C E , A K R O N , C O : 1 9 9 7

0

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

1 6 2 2 2 8 2 8 1 4 1 9 2 5 1

AD

ULT

S P

ER

TR

AP

RIB Strategy

• Uniform rootworm mating (exposed vs not

exposed) achieved more quickly

• Ear protection may be reduced due to

refuge pollen

2014 Tri River Area

Pest Management Workshop

101 Ag Insects

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• All single-toxin events have had

performance problems, which may or

may not be due to resistance

(environmental, rootworm abundance,

seed source)

• Two-toxin events seem to have fewer

problems

• Some evidence for Cry3 cross-

resistance

Rootworm Efficacy Issues

• Lab resistance is documented for all

events

• Level of expression

• Not high dose

• Not as effective as corn borer

events

Rootworm Efficacy Issues (cont.)

Documented Field Resistance

• Failures of cry3Bb1 events in NE Iowa

• Associated with continuous corn

(same event) and low refuge

compliance

• Many other reports, especially in NE

and CO

mCry3Aa root from Mesa County

• Take an IPM approach!

•Rotate

•Untraited hybrid + larval control

based on thresholds

•Adult control

•2-toxin events

•Spider mites

Confirmed Failures

• New events are in continual

development

•New Bt toxins and combinations

•RNA interference

•New non-Bt toxins

Rootworm Efficacy Issues (cont.)

2014 Tri River Area

Pest Management Workshop

101 Ag Insects

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• Double stranded RNA

applied to plant

• broken into small

interference RNA

• binds to messenger

RNA preventing

formation of key DNA

Crop rotation is an highly effective

nonchemical control if economics permit

• Larvae have narrow host range

• Newly hatched larvae have limited mobility

• Eggs are laid in current crop

• If following crop is not corn -- larvae starve

CHEMICAL CONTROL STRATEGIES FOR

WESTERN CORN ROOTWORM

EGG LARVA PUPA ADULT

SEPTEMBER – JUNE

JUNE -JULY

JULY -AUGUST

JULY -SEPTEMBER

SOIL TREATMENTS

SEED TREATMENTS

TRANSGENIC HYBRID

GRANULES OR

LIQUIDS BY

GROUND OR

SPRINKLER

LIQUIDS BY AIR,

GROUND OR

SPRINKLER

PRE-EMERGE

TREATMENT DECISION

• One scouting report in prior season with

more than 18,000 beetles per acre

• Unscouted continuous corn

PRE-EMERGENCE PERFORMANCE: 1987 – 2006 POSTEMERGE

TREATMENT DECISION

• One scouting report in prior season with more than 18,000 beetles per acre

• Unscouted continuous corn

• 1 – 2 larvae per root system• >8 on a single-trait is indication of failure

2014 Tri River Area

Pest Management Workshop

101 Ag Insects

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POST-EMERGENCE PERFORMANCE: 1987 – 2005 POSTEMERGE -- CHEMIGATION

Lorsban 4E*, 1 lb (ai)/acre

1.2 root rating, 182 bu/acre

Untreated

3.8 root rating, 132 bu/acre

*Bifenthrin also reported to work well

ADULT TREATMENT DECISION

• 3 Beetles per 10 ear zones*

(2 for retreat)

• 6 Beetles per 10 plants*

(4 for retreat)

• 6 Beetles per trap per day

(4 for retreat)

*(30,000 plants/acre)

ADULT TREATMENT TIMING

• At or above the decision level

• 10% gravid females

• 2 – 3 weeks after first beetle

ADULT TREATMENT EFFICACY(1992, 1 - 6 ROOT RATING)

Adult control (1991) 2.2

Larval control (1992) 3.8

Untreated (1991, 1992) 5.1

Properly timed western corn

rootworm adult treatments

can occur during pollen shed:

POLLINATOR PROTECTION

IS REQUIRED!

2014 Tri River Area

Pest Management Workshop

101 Ag Insects

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TSM BGM

CORN SPIDER MITES

TSM BGM

TYPICAL CORN SPIDER MITE SOURCESCORN SPIDER MITES:

RESPONSE TO DIMETHOATE

0

2

4

6

8

10

12

14

16

18

Texas Colorado

Mea

n LD

50

TSMBGM

• BGM is native

• Pest of various grass crops

• Key pest of Colorado corn

CORN SPIDER MITES:

PEST STATUS

• Egg, 3 immature stages, adult

• Egg to adult in 10 – 20 days

• In lab, 70x increase per generation

CORN SPIDER MITES:

LIFE CYCLE (BGM)

2014 Tri River Area

Pest Management Workshop

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• Overwinter as orange-yellow

fertilized females on alternate grass

hosts

• Walk or “balloon” back to corn in

spring

CORN SPIDER MITES:

LIFE CYCLE (BGM)

• Infestations start on undersides

of lower leaves

• Gradually move into upper part

of plant

• Most damage occurs between

pollen shed and denting

CORN SPIDER MITES:

LIFE CYCLE (BGM)

Severe BGM injury results first in death

of leaf edges, then the entire leaf

Grain yield loss over 25 years at Rocky Ford – 22%

Dry matter loss in 3 silage studies – 25%

• Drought stress

• Post-reproductive growth stages

• No TSM

• Insecticides

• Low rainfall

• Few natural enemies

• >95F temperatures

CORN SPIDER MITES:

FACTORS FAVORING BGM

INFLUENCE OF IRRIGATION

ON CORN SPIDER MITES

Iliff – 2007

0

50

100

150

200

250

300

Linear Wiper

Mit

es

pe

r P

lan

t

Limited Full

2014 Tri River Area

Pest Management Workshop

101 Ag Insects

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CORN SPIDER MITES:

Response to insecticide treatment

0

10

20

30

40

50

60

Penncap M, 1 pt. Untreated

Sq.

In. L

eaf A

rea

Dam

aged

Biological control is often the

only control needed for spider

mites in corn

Spider Mite Management Options

• Preserve biological control

• Preventive miticides

• Reactive miticides

• Preventive vs. reactive depends on

local resistance problems, other pests

• Crop near tasseling?

• Most plants infested?

• Parts of crop drought stressed?

• Mite predators scarce?

CORN SPIDER MITES:

PREVENTIVE MITICIDE QUESTIONS

• Max temps ≥ 95°F for next 2 weeks?

• Field history of mite problems?

• TSM problems expected?

≥3 “Yes” answers indicates reasonable

need for preventive treatment

CORN SPIDER MITES:

PREVENTIVE MITICIDE QUESTIONS

PREVENTIVE MITICIDES Rank in trial

*Total treatments in trial in ()

2006 2007 2010 2011 2013

(26*) (20) (20) (20 & 16) (20 & 20)

Onager 1E, 10 oz 1 1 1 9 & 4 9

Oberon 4SC + dimethoate,

4 + 16 oz 2 4 2 8 --

Oberon 4SC, 4 oz 4 12 9 17 & 13 8

Comite II + dimethoate,

36 + 16 oz 5 8 10 6 --

Comite II, 36 oz 24 20 19 13 --

Zeal 72W, 2 oz** 18 -- -- 10 6

Portal, 32 oz -- -- -- 6 11

*Total treatments in trial

**Not registered

2014 Tri River Area

Pest Management Workshop

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• Damage in lower 1/3 of plant and

colonies in middle 1/3

• Texas A&M dynamic threshold

CORN SPIDER MITES:

ACTION THRESHOLDS

Reactive Treatments

REACTIVE MITICIDES

Rank in trial

*Total treatments in trial

** Not registered until 2014

2000 2001 2004 2005 2006 2007 2011 2013

(12*) (14) (18) (15) (26) (20) (20 & 16) (20 & 20)

bifenthrin 3 6 8 9 23 14 20 & 8 --

bifenthrin +

dimethoate1 3 1 8 6 5 2 1 & 4

dimethoate 10 11 15 14 19 6 16 11 & 5

Agri-Mek** 6 1 2 1 7 -- 1 3

Portal -- -- -- -- -- -- 11 2

• 3 GPA minimum

• Control improves up to 5 GPA,

perhaps higher

• Buffer dimethoate

• Surfactants?