Tipping the Scale: First Emergence & Management of San Jose Scale. June 11th, 2020

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

Brief: San Jose Scale Emergence was observed this morning. In blocks where SJS was found during the 2019 harvest AND no management had been applied up to this point during the season, management should begin during the first available application window. Contact insecticides effective against scale (below) should be applied at the earliest application window. Clear skies and low wind conditions are forecast for the next five days.

Codling Moth has been causing economic fruit injury as adults continue to lay eggs and larva continue to emerge, producing damage to fruit in untreated blocks. Management for both San Jose scale and codling moth should be strongly considered this week.

Depth: San Jose Scale crawlers will be making their way from beneath the female hard shell to settle on branches, foliage and fruit to begin feeding this week. SJS emergence will continue over the next 4 weeks and will require 2 applications of contact insecticides at a 14 day interval or a combination of a contact and a systemic at the earliest application window. It will take about 10 days before feeding damage to fruit becomes visible as very small red spots on the fruit surface.

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.

The developing crawler is most vulnerable upon emergence and excellent coverage is required for the application to be effective. Dense foliage will shadow the fruit and reduce the effectiveness of the application. Slower tractor speed and higher volume should be considered based on tree canopy density.

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. Post bloom 1st and 2nd crawler emergence options are still effective given good application coverage and timing.

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 highly recommended)
* 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 – based on coverage)
* Endigo ZC 5-6 fl oz/acre (Moderate)

Systemic Insecticide
* Movento 240SC at 6-9 fl oz/acre PF-1C (High) (oil or penetrant required) should be made 2-3 weeks prior to emergence or with the 1st contact application. For Movento to be used during crawler emergence it must also be used with a contact insecticide.

Given the need for codling moth management, Besiege would be a good option. Besiege in group 3A/28 (Lambda-cyhalothrin (active in Warrior) / Chlorantraniliprole (Active in Altacor) has been found to have a high degree of efficacy for codling moth and San Jose scale.

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 Movento 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. The use of this product now will also need a contact insecticide to kill emerging crawlers this week.

Movento should be active in 10 to 14 days. That said, if drought conditions continue it may take additional time to activate the material in the trees vascular system (no data to support this but I have seen this occur in trees injected with insecticides).