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Scales found in Walnut: Identification, Life Cycles, & Management Timing

Dani Lightle UCCE Farm Advisor, Glenn, Butte & Tehama Cos. February 6, 2015

Botryosphaeria lesions under walnut scale

Scale populations are increasing

Photos: T. Michailides

Outline:

1. Scale species common in walnut

2. Scale lifecycles

3. Management timings and options

Most common scale species: walnut scale

Daisy-like scalloped margins

Most common scale species: walnut scale

Tree symptoms with high populations: • Branch dieback • Splitting bark • May appear water stressed

Frequently encountered scale species:

European fruit lecanium Frosted scale

Rounded, army-helmet shape

European fruit lecanium versus frosted scale:

Identical most of the year White waxy coating on Frosted scale only during March-April

Lesser common scale species:

San Jose Scale Circular with raised ‘nipple’

Lesser common scale species:

Italian Pear Scale

San Jose Scale Circular with raised ‘nipple’

Associated with Lichens

Generic scale lifecycle: eggs

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Generic scale lifecycle

Unhatched eggs

Generic scale lifecycle

Eggshells

Generic scale lifecycle

Crawlers

Generic scale lifecycle: crawlers

Adult spider mite

Scale crawler

Generic scale lifecycle: nymph development

Lose: ‒ Legs ‒ Eyes ‒ Antennae

Gain: + Scale cover + Rudimentary eye

spots (if male)

Generic scale lifecycle: females versus males

Female: no eye spots, legs, or antennae Male: eye spots, penile sheath

Generic scale lifecycle: females versus males

Adult male: Winged, flies to females

Walnut Scale Lifecycle

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Walnut Scale Males

Crawlers

Males

Crawlers

Development Nymph

Development 2nd instar

• 2 generations per year • Overwinter as 2nd instar nymph

Adult females

Frosted Scale / European Fruit Lecanium Lifecycle

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Eggs

Rapid

growth

into

adults Frosted Scale

2nd instar 2nd instar

1st instar rs Crawlers Crawlers

• 1 generation per year

Frosted Scale / European Fruit Lecanium Lifecycle

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Eggs

Rapid

growth

into

adults Frosted Scale

2nd instar 2nd instar

1st instar rs Crawlers Crawlers

• 1 generation per year • Overwinter as 2nd instar nymph

Managing scale: in-season monitoring

Have monitoring tapes out by early May

Double-sided tape

Check regularly with a hand lens

Managing scale: in-season monitoring

Scale tape under more powerful magnification

Often high densities at margins of tape

Scale Monitoring: Red Bluff 2014 – Walnut Scale

0

10

20

30

40

50

60 A

vg. #

of

Cra

wle

rs /

Day

Average Number of Crawlers per Day

Scale Monitoring: Red Bluff 2014 – Walnut Scale

0

10

20

30

40

50

60 A

vg. #

of

Cra

wle

rs /

Day

Average Number of Crawlers per Day

0

10

20

30

40

50

60 A

vg. #

of

Cra

wle

rs /

Day

Average Number of Crawlers per Day

Aug. 23rd Assail, 8oz/ac

Scale Monitoring: Red Bluff 2014 – Walnut Scale

0

10

20

30

40

50

60 A

vg. #

of

Cra

wle

rs /

Day

Average Number of Crawlers per Day

Aug. 23rd Assail, 8oz/ ac

Sep. 22nd Harvest

Scale Monitoring: Red Bluff 2014 – Walnut Scale

0

1

2

3

4

5

6

7

8

Avg

. # o

f C

raw

lers

/ D

ay

Average Number of Crawlers per Day

Aug. 23rd Assail, 8oz/ ac

Sep. 22nd Harvest

Scale Monitoring: Red Bluff 2014 – Frosted Scale

Managing scale: treatment timings & options

Timings: Delayed dormant (bud swell until flowering) Crawler stage - research suggests may be more effective timing

Managing scale: treatment timings & options

Timings: Delayed dormant (bud swell until flowering) Crawler stage - research suggests may be more effective timing

Organic treatment options: Organic option: oils -Don’t apply when dormant! Narrow range oils during summer: -Watch for phytotoxicity

Managing scale: Current Research into Control Options Lead researchers: B. Van Steenwyk, C. Wise, J. Hasey

Methods: • 4 replicates in Vina walnuts • Each tree monitored with sticky tape -- March 25th – June 2nd - First crawlers: April 23rd • Treatments applied:

- Post Delayed Dormant – April 8 - Crawler stage: May 6

Study treatments

Treatments: Post Delayed Dormant (April 8): Centaur 70 WDG Seize 35 WP Crawler Stage (May 6): Movento 2SC Assail 30SG Assail 30SG Brigadier 2EC Closer 2SC Centaur 70 WDG Untreated check

Rate Form/ ac: 46.0 oz 5.0 oz 9.0 fl. oz 9.6 oz 5.3 oz 12.8 fl. oz 5.75 fl. oz 46.0 oz ---

Results: Mean Crawlers / Day: May 12 – June 2, 2014

0

5

10

15

20

25

Untreated check

Centaur 70 WDG

(delayed dormant)

Seize 35WP (delayed dormant)

Assail 30SG Assail 30SG Movento 2SC

Brigadier 2EC

Closer 2SC Centaur 70 WDG

Mea

n c

raw

lers

/ cm

/ d

ay a a

a

bc

c

b

(5.3 oz/ac) (9.6 oz/ac)

a

d

bc

0

1

2

3

4

Untreated check

Centaur 70 WDG

(delayed dormant)

Seize 35WP (delayed dormant)

Assail 30SG Assail 30SG Movento 2SC

Brigadier 2EC

Closer 2SC Centaur 70 WDG

# liv

e sc

ale

/ cm

ab

c c

bc

c

a

bc

c c

Results: Live Scale / cm: Jan 21, 2015

(5.3 oz/ac) (9.6 oz/ac)

Questions??

Contact me: dmlightle@ucanr.edu 530-865-1153

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Eggs

Rapid growth

into adults

Walnut Scale

Frosted Scale

Males

Crawlers

Males

Crawlers

Nymph development

2nd instar

Nymph Development 2nd instar

2nd instar

1st instar Crawlers Crawlers

0

10

20

30

40

50

60

Avg

. # o

f C

raw

lers

/

Day

Aug. 23rd Assail, 8oz/ ac

Sep. 22nd Harvest

Scale Monitoring: Red Bluff 2014 – Walnut Scale

0

2

4

6

8

Avg

. # o

f C

raw

lers

/ D

ay

Aug. 23rd Assail, 8oz/ ac

Sep. 22nd Harvest

Scale Monitoring: Red Bluff 2014 – Frosted Scale