Chris Walsh and Kathy Hunt, Department of Plant Science and Landscape Architecture, University of Maryland,
An unusually cool, wet spring, followed by hot, dry summer weather, has affected apple fruits and apple trees.
Sunburn and abnormal red color development were seen on early ripening varieties at the UMD orchard in Keedysville. Sunburn on the cheek of an early-ripening red variety is shown in Figure 1. While the red blush looks normal on this photo, red color in some other early-ripening apples appeared orange or muddy brown. Hopefully, the color will turn brighter with cooler weather, but there’s not a lot of time left before early varieties ripen and are ready for picking. Talking with growers and farm advisors from Virginia to the Hudson Valley, apples will likely be picked seven to ten days ahead of ‘normal.’
If you are concerned by the prospect of an early apple harvest, consider applying AVG. This plant growth regulator, marketed as ReTainTM , delays the onset of ethylene biosynthesis, allowing apple harvest to be delayed for one to two weeks. If this is of interest, be sure to read the ReTain label carefully to determine the proper concentration and timing for your orchard.
With the hot dry weather, springtime shoot blight is now quite easy to spot. In a trial block at Keedysville, we did not apply streptomycin to control blight. In addition, no attempt was made to prune out blighted shoots. Figure 2 shows a tree which was quite susceptible to blight. In that Figure, the tree had more than 50 blighted shoots.
Fireblight susceptibility is important to consider when planting new orchards. Growers need to identify and plant blight-resistant blocks that can produce good quality, flavorful fruit to combat the future effects of climate change.
