Brief: The first San Jose scale (SJS) adult males began their flight on the 18th of May (biofix date). The NEWA model states the range of first generation crawler emergence is predicted to occur approximately 260-360 DD (base 50F) after the biofix (See Scouting Report).
As we are at the onset of the emergence today, using the weather station in Highland (HVRL), we began to lift female scale under a microscope to assess crawler develop on infested trees. After evaluating 50 SJS infestations from glden and delicious trees today, it appears the crawlers are incomplete in their development and will require a few days for completion. Given upcoming cool temperatures development will be slow over the next two days.
We have placed black electrical tape and Vasoline on limbs of infested trees to monitor for crawler emergence over the coming days until emergence begins and will post emergence once it occurs.
Management of Crawlers:
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 management applications.
At this period of SJS management the options include the use of of oil, precisely timed contact insecticides, and insect growth regulators.
Movento 240SC (spriotetramat), if employed, will need to be used with a penetrant (such as horticultural oil at 0.25%) along with a contact insecticide at this time as Movento requires additional time to become systemically active throughout the tree canopy to control crawlers.
The OP Imidan 70WP Phosmet (Class 2) and pyrethroids (Class 3) 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.
Besiege Chlorantraniliprole/Lambda-cyhalothrin (previously Voliam Xpress) has a high rating for activity against SJS. It is labeled in NY against a wide range of pests of pome fruit and stone fruit. The pome fruit label includes internal worms and leafrollers, aphids, (excluding woolly apple aphid), apple maggot and cherry fruit fly adults, leafhoppers, leafminers, plum curculio, Japanese beetle, pear psylla, plant bugs, stink bugs, and other caterpillars. The stone fruit label also includes peachtree and American plum borers. It has a high bee poisoning hazard.
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.
The Cornell fact sheet describes in depth San Jose Scale life cycle and biology.
