Intro: San Jose scale Quadraspidiotus perniciosus (Comstock) (SJS) has been in nearly every Hudson Valley orchard I’ve visited over the past ten years. Yet most growers have done well at keeping this insect from producing extensive losses since they have put the pest on their list to manage more closely. Management of this insect does require season long scheduling of directed applications to gain acceptable levels of control. We are approaching the emergence of SJS crawlers and precise timing of insecticide applications is critical to obtain control as the nymphs emerge.
We have two to three generations of San Jose scale each year. The SJS overwinters as immature blackcaps; adults mature during the bloom period. Males emerge and mate near petal fall. First-generation crawlers is our concern this week and will begin appearing in early June in southern areas and continue for a month. These crawlers develop into mature adults by late July.
SJS Crawler Modeling: The first flight in Highland occurred on the 19th of May. The model we are using
employs a 51°F lower threshold and 90°F upper threshold, for 400 DD after the beginning of the male flight so as to have insecticide available as the crawler emergence begins. As of 6/4/2017, 273 DD base 50F BE have occurred at the Highland station. Given the weekly forecasts and increasing temperatures we expect to see emergence beginning on 17th of June.
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.
Management: San Jose scale (SJS) requires close monitoring during harvest to detect and isolate fruit damaged by early developing SJS populations. The use of pheromone traps to monitor male San Jose scale flights are placed in May and the use of double-sided sticky tape can be employed for monitoring crawlers in early to mid-June. Any signs of 1st year damage should be followed diligently during the spring to address fruit injury from the previous year with applications of oil, precisely timed contact insecticides, insect growth regulators and or spriotetramat.
Depending on the mode of action of the material, applications of contact insecticides and insect growth regulators (IGR’s) will be made against the crawlers, effective when applied shortly after emergence using two back to back applications to cover the complete emergence of the insect..
Post bloom crawler emergence options at PF-2C (2-3 weeks prior to crawler emergence):
* Movento SC (spirotetramat) plus a penetrant at 0.25% / 100gal.
Post bloom crawler emergence options include contact insecticides at nymph emergence :
* (pyrethroids, OP’s, Neonicotinoids and pre-mixed formulations)
Movento requires a two week window prior to emergence, and as such, will be increasingly ineffective for this early stage of emergence. However, If you’re trying to clean up a robust population, Movento PLUS OIL or a penetrant such as LI700 at a penetrating rate should be applied along with a contact insecticide to manage this early stage of emergence. The active ingredient in Movento, spirotetramat, 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 to effectively control the 1st generation of the insect.
The OP Imidan 70WP and pyrethroids can also be used against the crawlers during emergence in back to back applications at 7-10 days.
Assail (Class 4) is a broad-spectrum neonicotinoid that also most effective when directed against crawlers as they emerge. The use of 0.25% may increase efficacy.
Centaur 0.7WDG ((buprofezin, IRAC Group 16) acts to inhibit the synthesis of chitin working as an insect growth regulator (IGR). Esteem 35WP (pyriproxifen, IRAC Group 7C), also an IGR, functions as a juvenile hormone mimic, inhibiting metamorphosis from one stage to another. These insecticides are most effective when directed against adults during the pre-bloom early post bloom period. They can be used against crawlers at first appearance yet have no contact toxicity and tend to act slowly. The efficacy of these materials is improved by the addition of oil, however, Esteem 35WP, Centaur 0.7WDG and Assail can be used effectively without the use of oil.
Remember, rotating classes of insecticides for each generation will delay the onset of resistance. Making multiple applications of the same class or same insecticide at a 7-10-day interval for the same generation is recommended.
For organic tree fruit growers, oil is the best cure for SJS. Kaolin Clay, the active ingredient of Surround WP, has no efficacy against the emerging crawlers. Keep oil away from applications of sulfur used for disease management to avoid phytotoxicity to fruit and foliage.