INDUSTRY NEWS
Cold damage on almonds : spring 2024
By Peter Reynolds , Yenda Producers Senior Horticulturalist – Nut Specialist
DURING the almond flowering season of spring 2024 there has been significant , if somewhat patchy , damage to the almond fruit caused by cold weather ( frost or freeze ). The Riverina almond growing region has sustained crop losses . It is hard to estimate a total area loss , however , it is reasonable to expect a significant overall yield reduction in the Riverina as a result . The damage has been seen on all the major varieties grown through the region with the later flowering and later fruit setting varieties the worst affected .
Spring freeze In August 2024 , during almond flowering , the Riverina saw some below 0 0 C nights which kept the frost fans busy , however there was no extensive frost damage noticed at that time . On 16 September 2024 , after the fruit had set ( petal fall to shuck fall stages ), the Riverina received one night of -2 0 C to -5 0 C and again the frost fans were working overtime . It was evident that there was some frost damage from that event , depending on location and stage of the fruit . Then on the 18-21 September 2024 , ( after shuck fall , susceptible fruit to 15mm diameter ) the area had both cold temperatures and cold winds ( 1 0 C but wind of 15 to 30km / hr and a wind chill factor of about -3 0 C ). During late September we noticed moderate to severe fruit drop on later set fruit and later flowering varieties . This drop continued into mid-October when the trees finished shedding all the damaged fruit . The early set fruit was already 20-25mm diameter and was not so easily affected . The are two main types of frost we receive in the almond growing areas : 1 . Radiation frost – this is the normal frost when the ground cools down and ice forms from the cold air , forming a white frost . In almonds this causes the conventional frost damage , usually during or at the end of flowering , as seen by a blackening of the internal part of the flower / fruit . See below above right .
2 . Advection Frost – this is where a cold air mass moves in and causes a “ freeze ” and does not need cold ground or clear skies . It can happen anytime during the day or night . This is the type of frost I believe has affected the almonds this season . The damage to the almond fruit ranges from totally brown internally , moderate browning around the edge to a tiny spot on the base of the kernel . Whatever the amount of damage , the fruit fell off the tree . See below :
This freeze damage could not have been avoided . I have inspected crops right under frost fans with significant freeze damage . In some cases , the fan did not operate as the thermometers did not fall below the starting temperature . Even where the fan was working , the fan just moved the cold air around . Both lower and higher areas of orchards were susceptible , it depended on the amount of shelter and the direction of the winds . Some orchards were badly affected and neighbouring orchards only a few kilometres away had no damage . The larger and earlier setting fruit ( Shasta , Non Pareil ) had some damage but the later setting flowers and varieties ( Carmel , Wood Colony , etc ) in the same orchard generally had more damage .
Spring / summer season strategy On the orchards that have had significant damage , it is easy to see that the affected trees have put on more vegetative growth than trees with a full crop load . This has made it difficult to manage where there are differing crop loads on the same orchard . It is important to assess the crop load once pit hardening is advanced or completed and then fine tune the water and fertiliser requirements for the remainder of the season . If the trees remain highly vegetative , they are more likely to go into a biennial cycle . If the trees make lots of flower buds in early 2025 , the tree could be overloaded for 2025-26 . If the trees remain very soft and leafy in January 2025 , they risk not forming enough flower buds for 2025-26 . I think it is important to use November and December to allow the trees to make sufficient shoots and spurs but to hold them back sufficiently , to harden the new growth and allow the trees to produce enough flower buds in early 2025 . Careful irrigation and fertiliser management is required for spring and summer to achieve this . Over fertilising during this time may also contribute to leaching and possible waste of fertiliser . Under fertilising may not provide enough nutrient for the tree ’ s requirements for bud formation . It is also very important to consider the post-harvest fertiliser and irrigation management , with a lower crop load this harvest , the trees may not need as much fertiliser after harvest but will need enough to carry over into next spring . Try to avoid new shoot growth in autumn as it will deplete the trees energy reserves . Other management techniques should be considered , such as , leaf and soil testing to assess nutrient levels , hedging or pruning to maintain good tree structure and maintain a good foliar spray program to help protect and nourish the extra leaf and shoot growth that has occurred over spring .
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