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

Why Has Red Scale Been Such a Problem and What Can You Do to Improve Control? Beth Grafton-Cardwell Dept 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 generations 2. To estimate populations at the end of the season*

First two generations of scales are synchronized and control works best on the first instars Male scale per card 20000 15000 10000 5000 550 DD 1650 DD 1100 DD Insecticides Insecticides Mixed stages On leaves, twigs and fruit 300 250 200 150 100 50 Crawlers per tape 0 13-Mar 27-Apr 11-Jun 26-Jul 9-Sep 24-Oct 0 Male Scale Crawlers

Spring High: 74 Low: 50 Degree day units Average daily temperature = (74+50)/2 minus LDT 53 = 62-53 = 9 degree days/day (61 days from male flight to crawlers) Summer High: 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 www.onsetcomp.com Hobo data loggers California red scale lower developmental threshold LDT=53 o F

3/3 3/18 4/2 4/17 5/2 5/17 6/1 6/16 7/1 7/16 7/31 8/15 8/30 9/14 9/29 10/14 10/29 11/13 11/28 California Red Scale DD Crawler emergence Lindcove Research and Extension Center 30 year Average 2010 2011 2015 2016 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 1 st gen 2 nd gen 3 rd gen 4 th gen 5 th gen

Why so much scale in 2012-16? Perfect storm 1. 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 4 th 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

What is happening in 2017? http://ucanr.edu/sites/kaccitrusentomology/ California Red Scale Degree Days at Lindcove REC 30 year Average 2016 2017 3500 3000 2500 2000 1500 1000 500 0 3 rd Crawler Emergence @2750 DD 2 nd Crawler Emergence @1650 DD 1 st Crawler Emergence @550 DD 3/3 3/18 4/2 4/17 5/2 5/17 6/1 6/16 7/1 7/167/318/158/30

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 generations 2. To estimate populations at the end of the season*

1000 Orchard 7 % fruit infested 0% 0% 0% CRS Males per card 800 600 400 200 Baythroid 4 th flight 0 3/19 4/2 4/16 4/30 5/14 5/28 6/11 6/25 7/9 7/23 8/6 8/20 9/3 9/17 Based on the Organophosphate era IGRs: lower male counts Aphytis and Movento: higher male counts CRS males

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

Spray coverage as measured by water sensitive paper D2/40 Engine-powered Air-O-Fan Sprayer 15 foot 40 year old Atwood navels Movento + 1% oil 500 gpa Inside Outside High 56% 62% Medium 72% 72% Low 83% 87% 250 gpa Inside Outside High 33% 34% Medium 61% 74% Low 72% 67%

Treatments for California red scale control Aphytis releases 100,000/acre distributed from Mar-Oct Oils 415, 440, 455 *OPs and Carbamates Lorsban, Supracide, Sevin Insect Growth Regulators Esteem 1998 Applaud/Centaur 1997 Lipid synthesis inhibitor Movento 2008 : foliar systemic *Resistance

Aphytis wasp releases Stage to Target: March-October 3 rd instar scales Efficacy: Works well on 2 nd and 3 rd 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.

Biological Red scale management 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/acre Cost: $.85/1,000 wasps = $85/acre August September Parasitized scales flake off

Petroleum Oils 415, 435, 440, 455 Stage to Target: 1 st or 2 nd generation 1 st 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 wellirrigated and treatments applied at night/early morning

Higher distillation point and higher concentration = greater scale kill, but be careful of phytotoxicity Effects of PureSpray oil (10E and 15E) on California red scale Untreated 415 1.2% 455 0.8% 455 1.2% 50 40 % Fruit infested with CRS 30 20 10 a ab bc c a ab bc c 0 % infested %>10 CRS

Organophosphates & Carbamates *Lorsban, *Supracide, *Sevin Stage to Target: 1 st or 2 nd 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: 1 st or 2 nd generation 1 st 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

Male scales molt more and so are more susceptible to IGRs = low pheromone trap counts Esteem Applaud

Tetronic acid insecticide Movento Stage to Target: younger instars Efficacy depends on Adjuvants Timing (tree has to move the product) Water volume Resistance: None Xylem: Upward transport 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 Phloem: Upward and downwar d

Pesticide screening 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 Insect growth regulators Movento (spirotetramat) Toxic 7c, 16 Soft Soft Very toxic 23 Soft Toxic Soft Oils Synchronize Reduce soft

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

High rates of neonicotinoids reduce scale on fruit October 2004 Neonicotinoid impact on red scale Assail and Admire Treated Untreated 30 25 % Infested Fruit 20 15 10 5 0 Assail 2oz Assail 5.7oz Assail 5.7oz Admire 32oz Apr 22 200 gpa Jun 22 900 gpa Aug 16 500 gpa May 7 irrigation

Scale/75 Leaf Sample Neonicotinoids do not control scales on leaves or twigs 2004- Assail Trial Assail Control 200 209 278 150 100 50 0 6/8 7/14 8/18 9/15 10/21 11/7 12/1 Treated on June 22, Assail 5.7 oz in 900 gpa

Scale/75 Leaf Sample Neonicotinoids do not control scales on leaves or twigs Admire Untreated 2001 Admire trial Kern Co. 200 150 100 Admire Lorsban 50 0 4/11 5/16 6/13 7/17 8/14 9/18 10/11 11/28 12/18 Admire applied May 21, Lorsban for citricola Oct 17

Why so much scale in 2012-16? Perfect storm 1. 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

Mean Number of CRS Males\Trap 60,000 50,000 40,000 May 18 th Pheromone dispensers added Control Pheromone Suterra Checkmate CRS slow release dispensers 30,000 20,000 10,000 180 dispensers/acre 0 12-May 12-Jun 12-Jul 12-Aug 12-Sep 12-Oct Date CRS/Twig (Aug) % Fruit with > 10 CRS Control 1.1/twig 13% Pheromone dispensers 0.3/twig 7%

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)