Freeze damage – Facts for Fancy Fruit

Freeze damage

Over the last week many areas of the state have experienced minimum temperatures likely to cause bud damage. Many areas experienced low temperatures of 24-26 F (according to weather stations) although one grower reported a low of 22 F.  As experienced growers know well, it’s not just the temperature as such that’s important, but the stage of crop development when it hits.

As you can see in Table 1, low temperatures of say 20F will likely cause significant bud damage to apples if crops are beyond the half-inch green stage. The same temperatures before this stage probably will not cause widespread damage.

So what happened this year? Most areas of the state experienced similar low temperatures, but since crops were at more advanced stages of development in southern areas, it’s there we see the most damage. In southern areas of the state, peaches have been badly hit, with close to complete crop loss in some cases. Apples have also been extensively damaged. Remember that even with 10% of buds alive (90% kill), we are often still looking at a full crop, and may still need to thin. After seeing extensive freeze damage to flowers or small fruitlets it may be tempting to not even consider the need for chemical thinning. Don’t fall into that trap. Luckily, we still have a little time, even in southern areas, before chemical thinning decisions need to be made. In more northern areas of the state, apples were often not as far along as tight cluster, so freeze damage would be expected to be minimal. Again, remember that if 10 or 20% of flowers are killed, this should be considered a form of early thinning and would not be expected to compromise the potential for a full crop.

Table 1. Spring temperatures that cause crop damage to apples and peaches.

Developmental stage 10% kill (°F) 90% kill (°F)
Silver tip 15 2
Green tip 18 10
Half-inch green 23 15
Tight cluster 27 21
Pink 28 25
Bloom 28 25
Petal fall 28 25
Swollen bud 18 2
Half-inch green 23 5
Pink 25 18
Bloom 27 24
Petal fall 28 25
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