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San Jose scale crawler management 2021

Exposed female SJS – 4/16/2021

With the relatively cool spring weather we have been having, the first large peak of San Jose scale crawler activity is delayed a couple of weeks this year compared to last year. I expect the first peak of activity to occur within approximately 10-14 days from now in Fort Valley, GA.

Following the degree day (DD) timing starting at February 1st using a base of 51oF and a max of 90oF, at this point last year we had accumulated 698 DD and this year we are at 537 DD (UGA Weather). I anticipate the first main peak of crawler activity to occur at approximately 700 DD since Feb. 1, which will be in a couple of weeks in Fort Valley. For the Ridge, I’d expect the peak about a week after Fort Valley and then the upstate a week or so after that.

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Closeup of a San Jose crawler on double-sided tape.

Remember that scale activity can be monitored relatively easy (although a bit tedious). Visually inspect limbs for live scale and/or wrap a branch with a strip of electrical tape plus a strip of double sided tape around that (see image below). Focus particularly on trees in blocks with a known history of scale issues.

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Monitoring San Jose scale crawlers with double-sided tape

Management of San Jose crawlers is not necessary for all blocks peaches if all blocks received two dormant oil applications this season. If a dormant spray was missed or you have a block with chronic scale issues, then I would suggest considering crawler management.

Once crawler activity begins to increase, consider management insect grower regulators, such as Esteem (6 oz/acre) or Centaur (34.5 oz/acre). Alternatively, when targeting the scale crawlers, Venerate XC (2 qt/acre applied twice over 7 day period; 4 qt total) or diatomaceous earth (i.e. Celite 610 @ 10 lb/acre) have both showed efficacy at suppressing San Jose scale.

If management occurs later, once the crawlers have already settled and/or you cannot find active crawlers in a block with a history of scale, it may be best to treat with Movento (6-9 fl oz/acre). Note that Movento should be applied once the trees have substantial leaf area, flushing new growth, and should be tank mixed with an adjuvant that has spreading and penetrating properties. Anecdotally, I have applied Movento late April and have had really good success.

As always, please check out the management guide for more detailed recommendations. And don’t hesitate to ">let me know if you have any questions.

Last thing, if you are bored and want to learn a bit more about, there is a new UGA circular about San Jose scale.

Take care, everyone!