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Tipping the Scales: Systemic San Jose Scale Management

San Jose scale on Empire

San Jose scale on Empire

We are predicting San Jose scale (SJS) crawler emergence on or about the 16th of June. If you had SJS on your fruit last season AND did not make applications against this insect during the pre-bloom period, the window for use of Movento would be for an application to be made no later then the 1st of June. Given this two week window, Movento applied with a penetrating non-ionic surfactant such as horticultural oil or the penetrant rate of LI700, will have just enough time to move into the foliage and stems to effectively control emerging crawlers that begin to feed on treated foliage and fruit. Be aware of the phytotoxicity that can occur when oil is applied within a Captain application window. Our research suggests that the use of a single application of Movento + penetrant using the high labeled rate of 9 fl.oz./A provided very good commercial control of the pest. (DATA TABLE)

However, if you chose to wait, treatments can be made against the San Jose scale (SJS) crawlers of the 1st generation applied by the end of next week based on model predictions. The best way to know when scale emerge in your orchard is to find SJS on 2-3 year old stems and wrap them with black electrical tape covered with Vasoline. The branches should be monitored daily on 5 days before and after the predicted date of emergence as the black background provides the contrast needed to see the crawlers.

San Jose Scale Established on apple stem

San Jose Scale Established on apple stem

overwintering San Jose Scale with live female (yellow)

overwintering San Jose Scale with live female (yellow)

SJS nymph monitoring with black electrical tape.

SJS nymph monitoring with black electrical tape.

A number of choices are available for SJS management. Centaur 0.7WDG acts to inhibit the synthesis of chitin (Class 16) working as an insect growth regulator (IGR). Esteem 35WP, also an IGR, functions as a juvenile hormone mimic, inhibiting metamorphosis from one stage to another (Class 7). These insecticides are most effective when directed against crawlers at first appearance yet have no contact toxicity and tend to act very slowly.

Assail (Class 4) is a broad-spectrum neonicotinoid that also is most effective when directed against crawlers as they emerge. The efficacy of these materials is improved by the addition of oil, however, Esteem 35WP and Assail can be used effectively without the use of oil. The OP Imidan 70WP and pyrethroids can also be used against the crawlers during emergence in back to back applications at 7-10 days.

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.
Updated insect modeling information can be accessed at http://treefruitipm.info/ within Cornell University’s Pesticide Decision System and Weather Pest Modeling web site.

For organic tree fruit growers, oil is the best cure for SJS as Kaolin Clay, the active ingredient of Surround WP, has no efficacy against the emerging crawlers.

San Jose Scale Established on Surround WP (Kaolin Clay) Treated Fruit