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Detecting early-stage frost damage for WA apple growers

Apple growers in Washington produce the majority of apples in the United States, however they are currently facing a number of obstacles this season. In addition to significant logistics challenges, growers have experienced very difficult winter conditions exacerbated by severe frost spells (sub 25 °F) in the past few weeks.  This has placed apple yields at risk. At or near bloom the margin for crop damage on apples is very narrow. According to Michigan State University, freezing temperatures of 28 °F will result in a 10% loss and 24 °F in a 90% loss. Narrowing in on areas in the orchard that might be more prone to damage or assessing damage early enough to mitigate losses will play a determining role in securing profitable yields this season.

The buds of apple flower clusters vary in their susceptibility to frost damage. The king bloom is more susceptible to frost damage during all stages of bud development, as they develop and bloom earlier than the side flowers. As such, the king blooms are often killed while the side blooms are undamaged. The extent of frost damage can be assessed by evaluating the king and side blooms separately. As the pistil is buried inside the base of apple flowers, it’s often necessary to tear the flower apart to see if its center is brown or black. 

Frost after bud break is detrimental to crop growth, as the newly formed leaves and flowers are not hardened against freezing conditions. The susceptibility of reproductive buds to freezing increases from bud break until full bloom, at which point frost is most detrimental. Research shows that the extent of damage depends on the intensity and duration of exposure to freezing temperatures. Early swollen buds can often withstand temperatures in the Farenheit teens, however, as the buds develop and open, temperatures in the low 20s can harm fruit buds and developing leaves. The longer these temperatures last, the more tissues and buds are affected. In addition, pest and disease pressure during spring can increase the susceptibility to frost damage, as they provide nucleation sites from which damaging ice crystals start to grow.

Short terms effects of frost include:

  • Death of buds (reduced sprouting)
  • Damaged king bloom (internal and external browning of flower parts)
  • Shorter effective pollination periods
  • Lower set (high post-bloom drop)
  • Suboptimal fruit development

Seasonal effects of frost include:

  • Lower yields
  • Reduced fruit quality
  • Increased potential alternate bearing

Early identification of frost damage will optimize your ability to mitigate the effects of frost and prevent any further losses. With high-resolution data on tree performance and transpiration, collected at set insights and paired with agronomic-based yield risk reports, you will know where your yields are most at risk from a quantitative and qualitative point of view. 

In-field measurements with the Aeroview InField mobile app (available for Android and iOS) to assess irrigation, nutrition, and soil can help you to identify and accurately quantify areas with suboptimal apple counts in time to make necessary adjustments.  

Request a demo to see how we can optimize your every footstep towards knowing, improving and securing your yield this season.

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