As we know, the devastating, invasive parasite Emerald Ash Borer has been making relentless inroads in the midwest throughout 2016.
Following are updates to round out the year in the news.
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Emerald Ash Borer May Become a Problem for Olive Growers
from Entomology Today:
In October 2014, researchers at Wright State University discovered that an invasive insect called the emerald ash borer (EAB) was attacking white fringetrees (Chionanthus virginicus) in addition to ash trees. This was big news at the time. The EAB had already killed tens of millions of ash trees, and the fact that it could harm another species made it even more devastating.
Now the same researchers have found that the EAB can also successfully complete development on olive trees. Professor Don Cipollini has found that the invasive green beetle can feed and successfully develop into adulthood on stems of the Manzanilla olive tree, a Spanish variety that yields green table olives and is grown widely around the world.
“We are showing in this experiment that emerald ash borer indeed can complete development on olive,” said Cipollini. “It would add a potential pest to the olive cultivation industry. If we see this happening in nature, it could be a huge deal.”
Geneticists on the cutting edge of an effort to save ash trees
On the Eastern Seaboard, forest biologists, molecular geneticists, bioassays, and others are collaborating on the genetic mechanisms by which some apparently EAB-resistant ash trees – “lingering ash trees,” as scientists are calling the relatively few which survive or escape – remain unsusceptible.
“Some trees were left that appeared very healthy with good canopies and not very many EAB exit holes,” Carlson said. “So those represent potentially resistant genotypes. There are definitely some biochemical or genetic responses—it’s an indication of some genetic basis to tolerance in the trees. There have been previous molecular studies comparing lingering versus fully susceptible green ash trees treated with EAB larvae.”
He noted that Jennifer Koch at the U.S. Forest Service Laboratory in Delaware, Ohio, has collected cuttings from many lingering trees after infestations and has developed a bioassay in which the cuttings are inoculated with eggs from EAB, and the growth of the larvae is assessed. Some of the tolerant trees slow or reduce growth of the larvae; some actually seem to kill the larvae.
Material from all the ashes in the plantation has been collected and is being tested in Carlson’s lab in search of a basis for genetic resistance, and the genomes of those trees that are left are being sequenced. The genomes of very susceptible trees also are being sequenced so they can be compared to see differences at the genome level that show resistance or potentially tolerant trees.
Tiny, Murderous Wasps Are Fighting The Bizarre Effects Of Climate Change
Emerald ash borers have destroyed 90 percent of the trees that once populated the ancestral lands of the Pokagon in Southwest Michigan. […] A couple years ago, the Pokagon turned their sights to a more natural enemy, one whose sole purpose in life is to attack, kill, and destroy the emerald ash borer. Well, two enemies, actually—both of them wasps that are so small, they’re barely perceptible to the human eye: Oobius agrili and Tetrastichus planipennisi. These parasitic insects spend their lives attached to borers, killing their hosts rather than surviving off of them. Oobius goes for the eggs, while Tetrastichus targets larvae. […]
Like the borer, these parasitoids come from China, where natural enemies keep both predator and prey in balance. Ben Slager, who runs the APHIS lab, says it helps when species co-evolve. “We definitely have predators here that go after emerald ash borers, but not with the same specificity as these do.” […]
In a 2015 study published in the Journal of Ecology using wasps reared in the lab, scientists observed a 90 percent decline in densities of live borer larvae in infested ash trees at two plots from 2009 to 2014. Though no significant differences were found in adult borer density, the decline in larvae density was correlated with the presence of Tetrastichus planipennisi, the same wasp the Pokagon are released on their land.
The lab estimates it will be seven years before wasps will make a demonstrable effect on the emerald ash borer.
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