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Crawling with Scale: San Jose Scale First Emergence & Management. June 17th

SJS 1st Gen. Nymphs on Black Electrical Tape (2018)

Synopsys: San Jose Scale Emergence was observed this morning. In blocks where SJS was found during the 2018 harvest AND no management had been applied up to this point during the season, then management should begin during the first available application window. Contact insecticides effective against scale should be applied at the earliest application window. Clear sky today and low wind conditions are forecast for this week with scattered showers beginning Tuesday.

For This Week, San Jose Scale crawlers are now emerging and will settle on fruit to begin feeding this week. Codling Moth has been causing economic fruit injury as adults continue to lay eggs and larva continue to emerge, producing as much as >10% damage to fruit in untreated blocks. Keep these two pests on your radar this week.

We can find San Jose Scale (SJS) in nearly every orchard block of apple in the Hudson Valley. Management of this insect requires season long scheduling of directed applications to gain acceptable levels of control. The need to manage SJS may increase over time once Lorsban is removed from the pest management tool box in 2012. Early season applications using 1-3% horticultural oil targeting overwintering adults at dormant through delayed dormant, with or without insecticides, can significantly reduce the population while reducing European Red mite. Finding the window around early season Captan use is challenging at best.

Overwintering SJS 'Black Cap' stage and damage to 2nd year apple stem.

Overwintering SJS ‘Black Cap’ stage and damage to 2nd year apple stem.

Biology: If San Jose scale has been found at harvest, trees with infested fruit should, without question, be managed during this period to keep fruit from becoming overrun a second year as significantly higher losses will certainly occur. Be mindful that a tree carrying a few SJS damaged fruit last season will become an eruption of fruit injury the following year if left unmanaged.

We have two to three generations of San Jose scale each year. The scale overwinters as immature blackcaps; adults mature during the bloom period. Males emerge and mate at petal fall. First-generation crawlers begin appearing in early June in southern areas and continue for a month. These crawlers develop into mature adults by late July. Second-generation adults appear from late July to early September; and, if a third generation occurs, it appears in late October to early November. The life cycle is completed in about 37 days. Crawlers can usually be found from early June until a hard frost in the fall.

To address the SJS issue, seasonal programs will require targeted applications of specific insecticides during three key periods of the season. Simply, in years to come, this insect has and will continue to cause sever losses in tree fruit due to lack of pre-bloom oil use (often due to the presence of Captan fungicide), the industry loss of broad spectrum insecticides such as Penncap-M and post-bloom Lorsban as well as increasing likelihood of insecticide resistance. Addressing the overwintering population should begin at the first application of the season shortly after snow melt and navigable ground conditions if a resident population is found either through trapping and scouting or presence of SJS during the 2018 packout.

San Jose Scale on Apple Trunk

Overwintering San Jose Scale Infestation on Apple Trunk

Monitoring: San Jose scale Quadraspidiotus perniciosus (Comstock) (SJS): is now transitioning from the ‘Black Cap’ overwintering stage to the crawler phase. Blackcap scale can be observed on 1st and 2nd year wood more easily then older wood as the branches will have a purplish hue. Cutting into the cambium will expose this color more vividly. You can observe the yellow females and males beneath individual ‘scale’ coverings where they will complete development, mate and bear live young or ‘crawlers’.

Crawlers are bright yellow and can be seen moving slowly on branches upon emergence. Once they settle down and begin feeding they will produce a white layer of chitin for protection known as the white cap phase. As they mature the covering changes to a darker or black cap phase during which they molt through three instar stages to become adults.

Management: Pre-bloom is by far the most opportune time to manage SJS. The overwintering immature stage, protected beneath the waxy covering are least protected from a spray application. However, developing foliage will increase ‘spray shadowing’ as the season progresses, reducing application effectiveness. A most effective timing during this period is delayed dormant, from the time silver tip begins to 1/2″ green.

Adult female beneath scale covering

Adult female beneath scale covering

We are all familiar with the use of horticultural oil, Lorsban, Esteem and Centaur directed against overwintered “black caps” during this period, as these are long-time standard control measures.

As the living scale need to breath and metabolize food they obtain from feeding on the sap of the tree beneath their chitinous shell, smothering the insect using 1-3% horticultural oil can be very effective alone or in combination with other insecticides.

Interrupting the nervous system function through the use of Lorsban, still labeled in NYS while the use of Esteem 35WP and Centaur provide can control the insect, without the need for oil as a penetrant, to disrupt SJS development.

As we approach the San Jose scale pest control options available to us are numerous, and to succeed, multiple strategies should be considered.

Post bloom 1st and 2nd crawler emergence options & (efficacy):
Contact insecticides pyrethroids, OP’s, Neonicotinoids and pre-mixed formulations

* Admire Pro 4.6SC 2.8 fl oz/acre (Moderate)
* Assail 30SG 8 oz/acre (Moderate)
* Beleaf 50SG 2.8 oz/acre (Moderate)
* Besiege 6-12 fl oz/acre (High)
* Centaur 0.7WDG 34.5 oz/acre (High) (oil or penetrant required)
* Esteem 35WP 4-5 oz/acre (High)
* Leverage 360 2.4-2.8 fl oz/acre (Moderate)
* Venerate XC 2.0-4.0 qt/acre (Moderate)
* Imidan 70W, 2.13-5.75 lb./acre (Moderate)
* Sivanto Prime 10.5-14.0 fl oz/acre (Moderate)
* Oil 1% post bloom (Moderate / High )
* Endigo ZC 5-6 fl oz/acre (Moderate)

Systemic Insecticide
* Movento 240SC 6-9 fl oz/acre PF-1C (High) (oil or penetrant required)
(2-3 weeks prior to emergence)

Remember, coverage is critical in scale management, requiring a slow travel speed (2.5 MPH), low wind speed (5 MPH) and as close to a dilute application as possible when using a contact insecticide. Increased foliage equates to “shadowing” and reduced coverage, which of course is the essential control component against the overwintering life stage.

Infestation levels that exceed just a few fruit at harvest in multiple blocks should be taken seriously. Even after a pre-bloom application is made, further management of populations should be considered as pockets of lingering scale in protected places such as the crotch angle of trees and underside of branches are likely, providing shelter from contact insecticides, allowing them to remain in the tree canopy.

As a follow-up to pre-bloom control of SJS, consider the use of Movento 240SC at 6-9 oz./A plus a non-ionic penetrant such as 0.25% to 1% agricultural oil or LI700 to address the San Jose Scale fruit injury at pack out last year.

1st gen. San Jose Scale 'crawler white cap phase' on Red Delicious shortly after June emergence.

1st gen. San Jose Scale ‘crawler white cap phase’ on Red Delicious shortly after June emergence.

Movento (spirotetramat), has been found to be most effective after PF in one to two applications, requires a penetrating non-ionic surfactant used at 0.25% (32 oz./100 gal.). The active ingredient in Movent is taken into the foliage, systemically moving through plant tissue to stems, roots, and leaves to be fed upon by emerging SJS nymphs during emergence and feeding. Our research has found the single application of 9 oz./A at PF or two applications at 6 oz./A at PF and 2C will effectively control the 1st generation of the insect.

That said, as crawlers are now emerging, the use of Movento for long term SJS management at this late stage of SJS emergence will require the use of a contact insecticide along with Movento to killl crawlers and allow the time needed for spirotetramat to move systemically into plant tissue to provide SJS control beginning in 10 days to two weeks.

Softer insecticides: Esteem 35WP (pyriproxyfen) can be employed with or without oil, acting against the pest as an insect growth regulator (IGR), a unique mode of action for use against the immature scale. As the insect matures, the insecticide acts as a juvenile hormone analog to reduce the insect capacity to molt.

Centaur 0.7WDG (buprofezin), also an IGR does require a penetrating non-ionic surfactant such as 0.25% v/v oil to be effective.

The bioInsecticide by Marrone BioInnovations ‘Venerate’ utilizes the active ingredient Burkholderia spp. strain A396, providing exoskeleton degradation and molting interference, active against the adult and crawler.

Incompatibility concerns over Captan use in early pest management programs for apple scab can be a formidable barrier when considering the use of oil. The possibility of phytotoxicity when using Captan near oil applications should be strongly considered when vying for a weather opportunity for SJS management windows.

Biological Control: The parasitoid wasp complex in New York, studied by Hodgkiss and Parrott in 1914, include Encarsia perniciosi (Tower, 1913), Aphelinus fuscipennis Howard and Aphelinus diaspidis. They found Encarsia perniciosi to be of greatest significance in parasitism of SJS. Subsequent analysis of SJS samples found parasitism rates predominately from Encarsia perniciosi ranging from 41% in unsprayed orchards in Virginia, and up to 95% in parasitism Wisconsin and Connecticut.

These parasitoids are a tiny, dark-coloured wasps, acting as biological control organisms of San Jose scale. Of Asian origin, Encarsia perniciosi prefers to lay its eggs into the second instar stage, yet will parasitize all life stages. The wasp larva matures, pupates inside its host, and upon emergence, chews through the scale covering, leaving behind a small ,1mm hole and mummified scale, reducing SJS in unmanaged trees.

Image: Encarsia perniciosi, parasitoid of San Jose Scale. INRA-HYPPZ, Institut National de la Recherche Agronomique, Bugwood.org
Creative Commons License licensed under a Creative Commons Attribution-Noncommercial 3.0 License.

SJS scale and parasitoid wasp emergence site.