The impacts of frost on fruit harvest
Frost, especially late frost during the flowering period, can be an unexpected setback for apple growers, and one out of their control. Understanding how a frost can affect the development of the fruit, and ultimately the yield of the crop is essential for producers, food manufacturers and consumers alike. Here we explore the implications of frost on apple crops, and the measures that can be taken to mitigate its impact.
Timing
Whilst the trees are resistant to the colder temperatures during other times of the season, they are particularly vulnerable to frost during the bud development stage, which occurs in early spring. In Orange, a late frost in September has impacted budding trees, especially the buds closest to the ground, which reached the lowest temperatures. During this flowering period, frost can kill the delicate flower buds, causing them to come away from the tree, and ultimately resulting in a reduced fruit yield for the season.
Types of frost
Radiation frost: This type of frost occurs on clear nights when heat escapes from the ground. This causes temperatures to drop rapidly, freezing buds and, hence causing damage.
Advection frost: This occurs when warm air is displaced by colder air, leading to widespread frost damage over large areas.
Both types of frost can have damaging and yield reducing effects on apple trees, particularly if it occurs during the flowering stage.
Consequences of frost damage
As a result of frost damage, the most significant impact, especially for a processing fruit grower – is a reduced fruit yield for the season. Other consequences include quality concerns with the fruit, since apples that survive a frost may not develop as they would have otherwise, affecting the size and shape of the fruit. This in turn can make processing less efficient.
Mitigation strategies
To combat the threat of frost damage, apple growers can use several strategies to manage what is in their control. The use of wind machines, sprinklers and heating techniques to raise the temperature around the trees can be effective during critical frost events. Some varieties of apples may be more resistant to frost, so ongoing research into frost-resistant apple varieties may offer long-term solutions for growers.
Placement of the orchard plays an important part. Orchards in areas less prone to frost typically have higher elevation and good air drainage, which can also help minimize risk.
Regardless of mitigation strategies implemented, frost damage is an ongoing inevitable challenge for apple growers, and one usually out of their control. Understanding the impact of frost on apple harvest is essential for everyone involved in the supply chain, from producers and processors to food manufacturers and consumers, since all parties are ultimately affected.
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