Sunburn protection: alternatives to hail nets

KNMI foresees increasingly hot summers in northern Europe. It could be said: the north is becoming the new south. For fruit growing, this brings new challenges. As the risk of sunburn in apples and pears increases. In high temperatures, apples and pears start to cook on the trees. Consequence? Burnt patches that even affect the flavour. As a fruit grower, what can you do about it?

Hail netting prevents direct radiation on hard fruit. This has been shown by a study by PCFruit. Just what are alternatives to hail nets to protect hard fruit from sunburn? In this blog, I describe the alternatives.

Southern sunburn strategies

In Spain and France, the risk of sunburn is higher than in northern Europe. Controlling sunburn is even more important there. What strategies are those fruit growers applying to control sunburn? And what alternatives are there to hail nets?

1. Spraying clay, lime or talc;
2. No summer pruning;
3. Sprinkling.

Broad weather insurance is not an alternative. In fact, sunburn is not covered in broad weather insurance.

Spraying clay or talc

The first alternative is to spray fruit trees. This can be done with a solution of white clay, lime or talc (such as Invelop). The white coating protects the apples and pears. It lowers the temperature and minimises the reflection of UV light. When it is not raining, this retains its effect for several weeks. This can also be a drawback. If you spray close to harvest and it doesn't rain, you will have to brush the fruit clean. There is also a chance that discolouration of the fruit will be left behind. Despite the possible disadvantages, spraying offers good protection against sunburn.

No summer pruning and thinning

The older the fruit trees, the lower the risk of sunburn. The more the fruit hangs in the shade, the less likely it is to get sunburn. You might therefore consider delaying summer pruning and thinning. This is to ensure that the apples and pears hang more in the shade. In doing so, however, there is a chance that fruit colouring may lag behind.

Sprinkling against sunburn

The best alternative to hail nets is sprinkling. To cool hard fruit, you can sprinkle it with clean sprinkler water. When you can sprinkle, you can tell the difference on the sprinkler between sprinkled and non-sprinkled. Sprinkling literally cools the fruit.

The only drawback: the sprinkling ban. In prolonged drought, water boards can ban sprinkling. As a fruit grower, you then cannot cool your apples and pears.

Conclusion

This blog describes alternatives to protect fruit from sunburn. Each strategy has disadvantages, but certainly also advantages! 

PS Did you know that long grass evaporates more moisture? Long grass therefore increases humidity. Therefore, postpone mowing grass strips on hot days.

Sources

Stan Verstegen van Groenten&Fruit: Hardfruit verbrandt aan de boom door hitte.

Ton van der Scheer van Groenten&Fruit: Hittegolf kan zonnebrand geven in appelteelt.

Jan van Liere van Nieuwe Oogst: Fruittelers willen beregenen tegen zonnebrand.

Rijksdienst voor Ondernemend Nederland: Brede weersverzekering 2023.

BFAO Onderlinge Fruittelers Hagelverzekering: Welk risico is verzekerd?

Vilt.be: Fruittelers kampen opnieuw met schade door zonnebrand.

Jeroen Verheul van Groenten&Fruit: Versneld afrijpen fruit.

Nederlandse Fruittelers Organisatie: Zonnebrandschade op niet beregende percelen.

Guus Daamen van Stal en Akker: Fruittelers moeten soms bijna de helft van hun appels weggooien.

Fruitteeltonline: Droogte en zonnebrand.

Other internal documentation.