Two researchers at Clemson University in the United States are finding short- and long-term solutions for fruit tree growers seeing harmful effects from climate change. Ksenija Gasic, Associate Professor of Horticulture Peach Genetics and Breeding, and Juan Carlos Melgar, Assistant Professor of Pomology (fruit growing) specialize in stone fruit trees. Melgar, a horticulturist, and Gasic, a breeder, chat with AgriExpo e-Magazine about climate-related threats and the various responses that mitigate damage.
AgriExpo e-Magazine: What climate issues are most impacting stone fruit trees right now?
Juan Carlos Melgar: There are two important issues. One is that trees such as peaches have a necessary dormant period to bloom properly in spring – in our region, it’s roughly 600 and 1,000 “chill hours” below 42 degrees Fahrenheit. But, our growers in the southeastern U.S. are seeing the effects of La Nina (cooler-than-average sea surface temperatures in the equatorial Pacific Ocean), which causes warm temperatures during fall.
The other big climatic issue is the occurrence of late freezes. The later you get a freeze – like when trees are in bloom and post-bloom – the more devastating the damage.
Ksenija Gasic: Because of a previously warm winter and a late freeze, last year many growers struggled just to keep trees alive, not even grow fruit.
AgriExpo e-Magazine: How do you help them translate research knowledge into actions that help their businesses?
Ksenija Gasic: My work offers a long-term solution because creating a cultivar takes 15 years. We find out which trees have the traits needed to respond to threats and incorporate them into a breeding program, creating new options for growers.
Juan Carlos: I help growers by understanding problems to take action right away – things like when to prune and even which branches to prune to mitigate the problems from caused by a warm winter or late frosts, or if they should use less fertilizer in the year following a warm autumn. There are also chemicals that help delay bloom so that you still can get some more chill hours, but we are learning these have to be applied within a small window or else they might cause more damage.
Ksenija Gasic: What growers want from me is to be able to tell them what is the cold requirement of the cultivars so they can decide which one to plant and understand the risks associated with the variable climate. In that way, they can work to get ahead of impending climate challenges.