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*
0
5000
10000
15000
20000
13-Mar 27-Apr 11-Jun 26-Jul 9-Sep 24-Oct
Ma
le s
ca
le p
er
ca
rd
0
50
100
150
200
250
300
Cra
wle
rs p
er
tap
e
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
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
3/3
3/1
8
4/2
4/1
7
5/2
5/1
7
6/1
6/1
6
7/1
7/1
6
7/3
1
8/1
5
8/3
0
9/1
4
9/2
9
10
/14
10
/29
11
/13
11
/28
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
0
500
1000
1500
2000
2500
3000
3500
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
0
200
400
600
800
1000
3/1
9
4/2
4/1
6
4/3
0
5/1
4
5/2
8
6/1
1
6/2
5
7/9
7/2
3
8/6
8/2
0
9/3
9/1
7
CR
S M
ale
s p
er c
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
0
10
20
30
40
50
% 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
0
5
10
15
20
25
30
% 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
0
50
100
150
200
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
0
50
100
150
200
4/11 5/16 6/13 7/17 8/14 9/18 10/11 11/28 12/18
Scale
/75 L
eaf
Sam
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
20,000
30,000
40,000
50,000
60,000
12-May 12-Jun 12-Jul 12-Aug 12-Sep 12-Oct
Me
an N
um
be
r o
f C
RS
Mal
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)