Why Has Red Scale Been Such a Problem and What Can You Do to Improve Control?

Beth Grafton-CardwellDept of Entomology, UC Riverside

Kearney Ag Center and Lindcove REC

•You can monitor and know when events are happening:

• Pheromone traps• Crawler tapes• % infested fruits

The squares represent 20% of the

card and so you can count scale in

the squares and multiply x 5 to

estimate the total number

Cards can be used two ways:1. To follow the generations2. To estimate populations at the

end of the season*

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13-Mar 27-Apr 11-Jun 26-Jul 9-Sep 24-Oct

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Male Scale Crawlers

550 DD

1100 DD

1650 DD

•First two generations of scales are synchronized and control works best on the

first instars

Insecticides

Insecticides

Mixed stages

On leaves, twigs

and fruit

Degree day unitsSpringHigh: 74

Low: 50

Average daily temperature = (74+50)/2 minus LDT 53

= 62-53

= 9 degree days/day

(61 days from male flight to crawlers)

SummerHigh: 103

Low: 81

Average daily temperature = (103+81)/2 minus LDT 53

= 92-53

= 39 degree days/day

(15 days from male flight to crawlers)

www.Avatel.com Harvest guard data loggers

California red scale

lower developmental threshold

LDT=53oF

www.onsetcomp.com Hobo data loggers

California Red Scale DD – Crawler emergenceLindcove Research and Extension Center

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30 year Average 2010 2011 2015 2016

1st gen

2nd gen

3rd gen

4th gen

5th gen

Why so much scale in 2012-16? Perfect storm1. Warm winters (2014-16) allow young stages to survive and

the generations are no longer synchronized in the spring, so the insecticides don’t work as well

2. Higher degree day units for the past 5 years allows the 4th

generation to grow up and the parasites can’t keep up with them

3. Drought – dusty, stressed trees have more scale, parasites don’t work as well when they have to get past the dust

California Red Scale Degree Days at Lindcove REC

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3/3 3/18 4/2 4/17 5/2 5/17 6/1 6/16 7/1 7/167/318/158/30

30 year Average 2016 2017

1st Crawler Emergence @550 DD

2nd Crawler Emergence @1650 DD

3rd Crawler Emergence @2750 DD

What is happening in 2017?

http://ucanr.edu/sites/KACCitrusEntomology/

The squares represent 20% of the

card and so you can count scale in

the squares and multiply x 5 to

estimate the total number

Cards can be used two ways:1. To follow the generations2. To estimate populations at the

end of the season*

Orchard 7

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CR

S M

ale

s p

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ard

CRS males

0% 0% 0%

% fruit infested

Baythroid

4th

flight

Based on the Organophosphate eraIGRs: lower male countsAphytis and Movento: higher male counts

At harvest check bins of fruit

Estimate the % of fruit

with >10 scales

If you find more than 5% of fruit

infested, the block likely needs a

treatment next year

Inside Outside

High 56% 62%

Medium 72% 72%

Low 83% 87%

Inside Outside

High 33% 34%

Medium 61% 74%

Low 72% 67%

500 gpa

250 gpa

Spray coverage as measured by water sensitive paperD2/40 Engine-powered Air-O-Fan Sprayer15 foot 40 year old Atwood navelsMovento + 1% oil

Aphytis releases

100,000/acre distributed from Mar-Oct

Oils

415, 440, 455

*OPs and Carbamates

Lorsban, Supracide, Sevin

Insect Growth Regulators

Esteem1998

Applaud/Centaur1997

Lipid synthesis inhibitor

Movento2008: foliar systemic

Treatments for

California red scale control

*Resistance

Aphytis wasp releases

Stage to Target: March-October 3rd instar scales

Efficacy: Works well on 2nd and 3rd instar scales, but not

1sts, molts or adults.

Resistance: None

Specificity: Only attacks California red scale

Natural enemies: other natural enemies such as

Comperiella and Rhyzobius join in

Issues: Some years its more effective than other years.

• Hot dry years seem to be more difficult.

• Most citricola scale, Fuller rose beetle treatments

(broad spectrum neonicotinoids) work against Aphytis.

Cultural Control:Reduce dust, prune trees, avoid broad spectrum pesticides,

and have a high pressure washer available Biological Control:Aphytis melinus: Release 5,000/acre every two weeks

from March 1 to October 31 = 100,000/acreCost: $.85/1,000 wasps = $85/acre

Biological Red scale management

August September

Parasitized scales flake off

Petroleum Oils

415, 435, 440, 455

Stage to Target: 1st or 2nd generation 1st instars

Efficacy: Works well on young stages, but allows enough

to survive that it doesn’t eliminate populations

Resistance: None

Specificity: Broad spectrum against both pests and

natural enemies, smothering

Toxicity to natural enemies: kills what it directly

contacts, but residues don’t last too long. Exception

is Euseius predatory mites are affected long-term.

Issues: During hot weather, the orchard must be well-

irrigated and treatments applied at night/early morning

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% infested %>10 CRS

% Fruit infested with CRS

Untreated 415 1.2% 455 0.8% 455 1.2%

Effects of PureSpray oil (10E and 15E) on California red scale

aab

bcc a ab

bc c

•Higher distillation point and higher concentration = greater scale kill, but

be careful of phytotoxicity

Organophosphates & Carbamates

*Lorsban, *Supracide, *Sevin

Stage to Target: 1st or 2nd generation white caps

Efficacy: varies, depends on resistance

Resistance: *common in the San Joaquin Valley

Specificity: broad spectrum, killing pests and natural

enemies unless they have resistance

Toxicity to natural enemies:

• High toxicity for Supracide and Sevin. Depends on

the rate for Lorsban.

• Aphytis, predatory mites, vedalia beetle have some

resistance in the San Joaquin Valley

Issues: worker safety (restricted use), drift, and

pesticide resistance

Insect Growth Regulators

Esteem and Applaud/Centaur

Stage to Target: 1st or 2nd generation 1st instars as they

start to molt.

Efficacy: Esteem was cheaper, shorter REI and perceived

to be more efficacious than Applaud and so has been

depended on for the past 15 years.

Resistance: Indications there is some Esteem resistance

Specificity: Works better on California red scale than

citricola scale or cottony cushion scale

Toxicity to natural enemies: Only toxic to coccinellid

predatory beetles such as Vedalia beetle.

Issues: coverage, timing and they only work on

developing stages (eggs and molts) – so they can’t

clean up a very heavy population

EsteemApplaud

•Male scales molt more and so are more susceptible to IGRs

= low pheromone trap counts

Tetronic acid insecticide

Movento

Stage to Target: younger instars

Efficacy depends on

• Adjuvants

• Timing (tree has to move the product)

• Water volume

Resistance: None

Specificity: Toxic to California red scale, citrus red mite,

citrus leafminer, citrus thrips

Toxicity to natural enemies: Affects predatory mites but

not predatory beetles or parasitic wasps

Issues: Uptake and movement into leaves and fruit.

Does not control scales on twigs and trunk. Can not

clean up a heavy population of red scale. Requires an

adjuvant.

and

Xylem: Upward

transport

Phloem: Upward

anddownwar

d

Insecticide group Chem

grp

Parasites Predatory

mites

Predatory

beetles

OP and Carbamate 1a,b Rate dependent Resistant resistant

Neonicotinoids 4a Toxic (9 wk) Rate &

coverage

dependent

Toxic

Insect growth

regulators

7c, 16 Soft Soft Very toxic

Movento

(spirotetramat)

23 Soft Toxic Soft

Oils Synchronize Reduce soft

Pesticide screening

Why are the systemic neonicotinoids (Admire Pro and generics, Assail, Platinum, Actara) not good products for California red scale?

•Reduce natural enemies•Systemics control red scale on fruit but not wood•Build up scale that can not be controlled by oils, IGRs or Movento

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% Infested

Fruit

Assail 2oz Assail 5.7oz Assail 5.7oz Admire 32oz

Treated Untreated

October 2004

Apr 22

200 gpa

Jun 22

900 gpa

Aug 16

500 gpa

May 7

irrigation

Neonicotinoid impact on red scale

Assail and Admire

•High rates of neonicotinoids reduce scale on fruit

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6/8 7/14 8/18 9/15 10/21 11/7 12/1

Sc

ale

/75

Le

af

Sa

mp

leAssail Control

2004- Assail Trial

Treated on June 22, Assail 5.7 oz in 900 gpa

278209

•Neonicotinoids do not control scales on leaves or twigs

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Scale

/75 L

eaf

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ple

Admire Untreated

2001 – Admire trial – Kern Co.

Admire applied May 21, Lorsban for citricola Oct 17

•Neonicotinoids do not control scales on leaves or twigs

AdmireLorsban

Why so much scale in 2012-16? Perfect storm1. Warm winters (2014-16) allow young stages to survive and

the generations are no longer synchronized in the spring, so the insecticides don’t work as well

2. Higher degree day units for the past 5 years adds another generation and the parasites can’t keep up with them

3. Drought – dusty, stressed trees have more scale, parasites don’t work as well when they have to get past the dust

4. Admire treatments and possibly Movento treatments are building scale on wood

5. The registered insecticides only last about 1 generation: great for light scale years and tough for heavy scale years.

Why don’t we have more red scale insecticides coming down the pike?

•The insecticide rate has to be high because water volume is high to achieve good coverage. •This often makes the product too costly or raises registration concerns

0

10,000

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Me

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RS

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es\

Trap

Date

Control Pheromone

May 18th

Pheromonedispensersadded

CRS/Twig (Aug) % Fruit with > 10 CRS

Control 1.1/twig 13%

Pheromone dispensers 0.3/twig 7%

180 dispensers/acre

Suterra Checkmate CRSslow release dispensers

What are we going to do about red scale?

Timing: hit the stage that is most sensitive and in tough situations apply multiple treatments

Good coverage: 750-1500 gpa for most chemicals, 250 gpa for Movento

Calibrate your rig correctly and Drive slowly! < 1.5 mph

Pheromone disruption: Suterra dispensers reduce scale about 50% in low to moderate populations

2017 should be better because we have had cold, wet winter weather (reduces dust, synchronizes scale, causes overwintering mortality of younger instars)