San Jose Scale Update – July 23, 2015

San Jose Scale damage has been seen on fruit in Norfolk, Grey, and Middlesex County. After hatching the scale crawlers will crawl for up to 24 hours until they find a suitable location to settle. This can either be on limbs, fruit, or even leaves. SJS feeding on fruit is most often found on the blossom and stem ends of the fruit, and can be identified by small grey patches surrounded by a red inflamed area. Severe infestations early in the season can even result in deformed fruit.

We are currently using two degree day models to monitor for San Jose Scale:Degree Day models

Based on these models we can predict crawler emergence. Only the Cornell model provides 2nd generation predictions.

SJS predictions July 23

There are two full generations of scale each year. We are expecting the second generation of adult males to begin flying soon, with the second generation of crawlers emerging in the first couple weeks of August.

In 2014 the Cornell model  was approximately a week ahead of crawler emergence. Summer insecticides Movento, Closer, and TwinGuard should target these crawlers. Movento is a slower acting insecticide and can be applied at the first sight of crawlers, if not earlier.  This generation of crawlers can last for up to six weeks, so reapplication of Movento in 14 days is optimal. Using Closer or Twinguard, growers can wait for a week after first crawlers are found to target a larger number of emerged crawlers. TwinGuard is well suited to the 2nd generation of crawlers that will be emerging soon.  Keep in mind that Twinguard contains Delegate when planning product rotation.  More information on insecticides can be found in Chapter 3 of Pub 360.

SJS damage on fruit

San Jose Scale damage found on fruit.

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