The warm, wet conditions persisting into the early days of autumn could dim Pennsylvania’s chances for a great fall foliage season in the coming weeks.
While the warm and wet summer delivered trees in great shape at the start of fall, for those trees to live up to their full potential and display their most vibrant fall colors they need cooler and drier weather now and in the next few weeks, according to Marc Abrams, professor of forest ecology and physiology in Penn State’s College of Agricultural Sciences.
“Due to the wet summer, this was shaping up to be a banner year for the foliage, but we need the weather now to cooperate and cool down,” said Abrams, who for nearly four decades has studied how seasonal precipitation and temperature influence timing and intensity of fall colors in Pennsylvania.
“With unusually warm weather predicted until the middle of October, I expect that will delay and somewhat diminish fall colors.”
Also, he noted, the very wet summer in most of Pennsylvania may increase leaf spotting fungus that also could diminish coloration in places.
His research indicates that clear, bright days, low but not freezing temperatures, and dry but not drought conditions promote the best fall colors.
Cooler temperatures signal deciduous trees to stop producing chlorophyll, the green pigment responsible for photosynthesis, he explained. The chlorophyll breaks down and disappears, unmasking other leaf pigments.
Those other pigments — xanthophylls and carotenes — create the yellows and oranges seen in the leaves of yellow poplar, hickory, sycamore, honey locust, birch, beech and certain maples.
After chlorophyll production ceases, trees also produce another pigment in their leaves called anthocyanin, according to Abrams. The anthocyanins create the brilliant reds and purples seen in maple, sassafras, sumac, black gum and scarlet oak.
“One thing that I have been impressed with in my nearly 40 years of gauging foliage is the resiliency of the display,” he said. “Year after year, despite the conditions, there are places where the trees show good color, but perhaps not great color every year.”
As Pennsylvania continues a warm and wet start of autumn, mosquitoes and ticks are likely to remain active, according to an annual seasonal projection from the National Pest Management Association.
“High temperatures and early rain could allow mosquito and tick populations to thrive well into fall,” the Bug Barometer forecast predicted for New England and the northeastern U.S., including Pennsylvania.
“A bitter winter is expected with colder temperatures and above-average snowfall, which will drive rodents promptly indoors.”
Based on weather patterns, long-term forecasts and pest biological behaviors, the group’s team of entomologists expects a similar spurt of increased pest activity across much of the U.S.
“As much as we all enjoy spending time outdoors and soaking in the summer weather, prolonged periods of warm temperatures throughout the U.S. will heighten pest pressure this fall, allowing stinging insects as well as disease-transmitting pests like ticks and mosquitoes to overstay their welcome in certain regions of the U.S.,” said Jim Fredericks, chief entomologist for the NPMA.
And, when temperatures begin to drop, residents across the country should remain vigilant for signs of unwanted invaders and take steps to keep pests out of their homes.
In addition to the pests highlighted by the NPMA, many homeowners across Pennsylvania have reported large numbers of brown marmorated stink bugs at the outdoor lights, windows and doors in the past week or so.
