In the crazy weather we’ve been experiencing lately, sunburn on fruit is a very real risk.
It’s different of course to the type of burn damage trees and fruit suffer in an actual fire (as many parts of Australia are currently experiencing), but if you live in a hot climate (like we do) sunburn is an inevitable part of fruit growing.
Sunburn can also happen in temperate fruit growing areas during heat waves, which unfortunately are becoming more common due to climate change.
There are three types of sunburn damage you may see on your fruit:
1. Sunburn necrosis
2. Sunburn browning
3. Photo-oxidative sunburn
In his first summer on the farm Ant (who leases our orchard) had a first-hand experience of sunburn, when a heatwave—a blistering day of 44C, hit the Pizzaz plums just before they were quite ripe enough to pick.
This was the result:
You can see the spots and shrivelling on the skin – that’s a version of sunburn browning. Most of the plums are still perfectly usable for jam, or cooking, or even for eating, but it definitely downgrades them.
The important question is, is it preventable?
It can be incredibly difficult in cases like this, where there was probably only a very brief window of a day or two when the plums were ripe enough to pick (with the confidence that they would continue to ripen off the tree) before the heat wave hit.
In a home garden, if you were paying careful attention to both your trees and the weather forecast, it may be possible to harvest the fruit (or at least some of it) in time. In Ant’s situation, where he’s managing the competing needs of 5,000 trees it’s much harder.
If you live in an area that experiences heatwaves there’s a number of other things you can do to prevent sunburn damage, including irrigation practices, pruning practices, and careful monitoring—we list 10 different ways to minimise sunburn in “What’s that spot? Common diseases of deciduous fruit trees” (even though sunburn is not actually a disease, but an environmental impact).
The main thing to do when a heat wave is predicted is to make sure your trees are getting enough water, which may mean watering every day.
And remember, the best time to water is either overnight or in the morning, to reduce evaporation.