Fruit trees are long term investments. Protecting those investments has grown more difficult as the vagrancies of changing weather patterns have caused problems. Soggy soils, severe hail, drought, extreme heat, changes in winter temperatures causing problems with chilling requirements, early breaking of dormancy and evolving insect and disease pressures are some of the challenges which are leaving even well-established orchards in flux.
The Climate Adaptation Fellowship has a mission to combine the knowledge of those who have been working the land with that of climate scientists to provide peer-to-peer outreach for farmers and foresters coping with climate change in the Northeast. Learning modules, available at www.adaptationfellows.net/tree-fruit, are focused on the scientific data regarding temperature, humidity, precipitation, soil moisture levels and more, along with the risks and opportunities these changes bring at the orchard level.
The impact of climate changes are just as real elsewhere. For growers in warmer climates, such as the southern U.S., Eike Luedeling, Department of Horticultural Sciences at the University of Bonn, Germany, has information on warming weather and the impact changing temperatures will have on fruit trees available at eikeluedeling.com/presentations/180813_IHC_Luedeling_warm_winter.pdf.
Penn State’s Extension website has a four-part series of short video presentations by Robert Crassweller, tree fruit specialist, discussing the changing climate and its impact on orchards available at extension.psu.edu/climate-change-and-orchards-part-1-what-changes-have-already-occurred. This information applies to orchard growers everywhere, as they learn to cope with a changing climate and its impact.
What to Expect
Crassweller also presented a workshop on climate change and tree fruit at the recent New England Vegetable & Fruit Conference. He discussed four general issues of concern for tree fruit growers: carbon dioxide levels; shifts in precipitation and temperature; extreme rain and hail events combined with variability in weather patterns; and changes in water availability.
All of these are going to impact the viability of tree fruit production, and farmers will need to manage their impacts. From site and rootstock selection to pruning techniques and irrigation management, the keys to successfully raising a fruit crop will be changing.
According to Crasswell, changing weather patterns should allow some extension of the growing season. Cultivars that are later-maturing may soon work in regions which are now too cold. While that opens up new opportunities, it’s also important to remember that spring warming events will increase, leaving early blooming varieties more susceptible to frost damage from a return to cold temperatures after warm spells, a problem which may increase in frequency. On the other hand, the earlier start to the season may allow for production of earlier maturing varieties.
Site selection will become even more important, as south-facing slopes will run a greater risk of excessively warm temperatures, promoting early bloom. Windbreaks will increase in importance, playing a role in protecting fruit trees from extreme weather including high winds, anticipated to occur unpredictably and with more frequency.
Because of changes in precipitation levels, including increased deluges and periods of saturated soils as well as periods of drought, growers are going to need to have irrigation in place. Having irrigation in the orchard, particularly to maintain growth of young trees, will be needed.
Extreme rainfall events will require changes in fungicide, herbicide and pesticide applications. Changing weather patterns will also mean new bugs and diseases, as well as a change in timing for some of the typical ones. In warmer weather, pests might be able to produce more generations – and do more damage – than they do now. Relying on the established patterns of application timing won’t work.
Warming temperatures will mean an increase in carbon dioxide levels, enhancing photosynthesis and potentially promoting canopy growth. Selecting rootstocks for less vigor could become necessary for some fruits.
Fruit will also be exposed to higher temperatures, potentially without nighttime cooling, and will not color properly. Increased exposure to intensive sunlight and high temperatures can also cause issues such as sunburn necrosis or sunburn browning, and related disorders.
Summer pruning will increase in importance, in order to optimize light filtration through the trees. Dormant pruning will start earlier in the winter, but fluctuations in temperature might make timing tricky. Less dormant pruning will be needed.
Bloom and post-bloom chemical applications may become more consistent with earlier springs. While chemical thinning of apples and pears might become less risky, peaches are going to need more thinning as high temperatures during and after bloom mean smaller fruit. Blossom thinning will become more important to obtain adequate peach sizing.
Weed control will become more complicated as weed growth will be enhanced, and as new weed species move into areas as the weather changes. Site preparation will become even more important, to remove weeds and guard against concerns such as replant disease. Extra care when establishing an orchard, focusing on soil organic matter and proper amendments, will give trees the healthiest start.
The use of high tunnels, shade cloths, hail netting and other protective measures is going to become more common. Not only will these protect fruit crops from extreme weather, they can also offer protection from pests. As invasive pests continue to threaten crops, pests which thrive in warmer climates move north and common pests are able to produce additional generations as growing seasons lengthen, the protection offered by covering fruit-producing plants might increasingly be worth the investment.
No matter what crop you grow, climate change is going to require alterations in the normal routine. But for growers of perennial crops, particularly fruit and nut trees, the challenge is cumulative, as the plants will suffer stressors from the changing conditions repeatedly, affecting their ability to bear fruit.