KIRTLAND, Ohio -- It took a scourge of black vine weevils for Dan Herms to finally see the phenological light.

The voracious Otiorhynchus sulcatus had suddenly began killing off shrubbery in the late 1990s at the nurseries in Lake County, east of Cleveland -- even though nursery owners for decades had been spraying them successfully with pesticide each June.

"We assumed it was that the insect had developed a tolerance to the chemical they were spraying in June to kill it," said Herms, an Ohio State University professor of entomology at the university's Ohio Agricultural Research and Development Center in Wooster.

"But it's also a hard pest to see because it feeds at night , so what they didn't know was that the weevil was already mature by the time they sprayed and had already done its damage."

The problem was that Lake County nursery managers were spraying on the same calendar day that they had for decades.

But research conducted by Herms and his predecessor at the center, David Nielsen, showed that weevil larvae were responding to gradual, incremental increases in the soil temperature and emerging as adults earlier to munch on ornamental shrubs, rhodedendrons and azaleas at the nurseries.

So in 2001, Herms suggested a change for Lake County growers.

"We got them off that calendar schedule and onto a biological calendar," Herms said. "We found that the larvae emergence was aligned specifically with the time when black locust trees bloom, so growers now wait for the locust tree and then spray for the weevil then -- instead of waiting until June."

That experience spurred Herms to cast a much wider phenological net to try to get a handle on ecological changes going on throughout in Ohio.

This spring marks the seventh straight year of what he calls the "phenological garden network," three dozen or so different plots around the state where volunteers and, in some cases, staff researchers, monitor the timing of blooms on a specific set of plants to track changes in the timing of the first bloom and full bloom.

It's the largest such network in North America and currently consists of 35 gardens plotted in arboreta, schools and OSU Extension offices. Each garden has 16 cultivated varieties with blooming periods that, collectively, span the growing season -- including early bloomers like forsythia and star magnolia and late bloomers such as Rose of Sharon and elderberry.

Each garden also has at least one type of lilac. Changes in the weevil emergence also correspond to other growing season changes shown in larger-scale lilac studies, Herms said.

The blooming data from Ohio lilacs is also used by the National Phenology Network.

Herms said his statewide project hasn't yet revealed hard data about a warming climate but it can be used both to compare to older, hand-written records and as a baseline for future studies.

"Obviously, seven years is too short of a time frame to already document climate change," he said. "But you can make inferences when you compare our data with some other measures of phenology on the same species."

But Herms and other researchers have reached several conclusions from the project:

• That the sequence in which phenological events occur stays the same each year, Herms said.

This is no small thing: It is only knowing that a certain plant species will bloom before another (and because it has accumulated enough 'heat units' to emerge) that allows scientists to accurately know when a specific pest that requires the same heat total will emerge.

• There is a "phenological wave" that moves south to north through Ohio, from the relative warmth of the Ohio River to the coolness of the lake, each year. In some years, the velocity of this wave is measured over a month, two weeks to reach Columbus and another two to make it to the lake. In other years, it races northward at almost immeasurable speed.

• Spring -- again, despite a slow year this year -- is generally coming earlier, when measured by the "first bloom" and "full bloom" of many plants throughout the state, specifically those that are more dependent on heat than soil quality or daylight hours.

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