Shady practice to combat apple sunburn
By Rebecca Darbyshire and Ian Goodwin
The 2016/17 ‘angry summer’ broke over 200 Australian extreme weather records. Much like the Australian population, apples suffer under these extreme heat conditions and can get sunburnt, which ranges from yellow discolouration to burns that penetrate the skin (Figure 1).
Sunburn reduces market yields by downgrading quality and increasing the amount of culled fruit. With human-induced climate change expected to increase the frequency and severity of extreme heat events, higher rates of sunburn are expected in Australian orchards.
Examples of sunburn damage of Royal Gala apple (L. McClymont, Agriculture Victoria).
A recent study has shown that sunburn risk will increase as climate change progresses and that netting can provide protection from this risk. It was found that the level of risk reduction netting provided depended on the growing region and future time period. The financial gains from installing netting will depend on the identified risk; benefits including lower irrigation rates, hail and bird protection, and production costs, including netting installation and production changes needed under nets.
The future risk of sunburn for non-netted and netted orchards was evaluated for ‘Royal Gala’ apple at 10 sites from different growing regions across Australia historically and for 2030, 2050 and 2090. The risk was calculated as the number of January days that could result in sunburn (Table 1).
Some sites were found to have little to no risk of sunburn out to 2090 (Spreyton, Huonville, Applethorpe). For more exposed sites, netting provided a notable reduction in the number of sunburn risk days, generally over a 50 per cent reduction (Batlow, Manjimup, Yarra Valley, Lenswood). For sites which currently experience high sunburn risk (Donnybrook, Tatura, Young), netting reduced future risk considerably; however, some risk was still recorded under netting. For instance, risk of sunburn under netting at Young in 2090 (7.8 days) was similar to that experienced at Donnybrook for non-netted orchards now (7.0 days).
Table 1 Historical and future risk of sunburn damage for Royal Gala apple. Data are the median number of January days that could lead to damage for non-netted and netted orchards.
For more information, visit link.springer.com/article/10.1007/s00484-016-1268-y or email [email protected].
Rebecca Darybshire is from the NSW Department of Primary Industries and Ian Goodwin is from Agriculture Victoria.