Wooly Adelgids


Tsuga canadensis the year we discovered Adelges tsugae (woolly adelgid)

HWA distribution courtesy NYS DEC

Bad news this year – walking across the creek bridge next to our house I got smacked in the face by a hemlock branch encrusted with Adelges tsugae (wooly adelgids). Currently a serious threat to Tsuga canadensis (hemlock) here in New York, adelgids can kill a tree in as little as four years by tapping directly into the trees food storage cells. One insect can be responsible for orginating as many as 40,000 descendants in a single season!

Hemlock distribution courtesy NYS Hemlock Initiative

This is a big deal in our neck of the woods. Hemlocks are the third most common tree in our forests, and are what is called a “foundation” species. This means they create the ecosystem where they resides. Also a climax species, they are members of a mature forest, and critical components of a clean water system.


We have been keeping an eye on the four mature hemlocks in a row here, and even now see not many more adelgids than these, but it is no more likely there are only the adelgids we see than there is only the one house mouse we caught… still, in a spirit of hopeless optimism inappropriate to our current political climate, my husband cut the branch off and burned it in the wood stove. We then sprayed the ground between the tree and the  house with isopropryl alchohol, ’cause some fell off, okay?


Zeb Strickland

We like these trees. They are close to the house but not TOO close (like the Norway spruce), and they hold the creek bank near where it likes to flood the road. Even though we assume the many, more ancient hemlocks in our woods won’t benefit much from stopping adelgids down here, we suddenly feel on the front lines of an invasion. These trees are on a direct path to a work site, and we don’t want to become vectors ourselves, spreading the little bastards to uninfected areas.So we have asked Forest and Water Solutions to come have a look.

I met Zeb back when I was part of the Cornell Botanic Gardens Natural Areas Academy for a few years. A great teacher, we spent some time discussing the pro and cons of pesticides and certification in their application. (I got to “shoot” some Japanese knotweed under his supervision, a highlight of my time there.) So we were already pretty confident when we contacted him, and his easy manner and thorough explanation of the process cinched it. We signed up for a single basal bark application for four trees.

Forest and Water Solutions

I was able to stand nearby and watch. It didn’t take long, or cost much. Zeb used two chemicals, one faster acting and the other good for five years or so. For those of you rightly concerned about the over use of pesticides, I was pleased to see how careful and contained the process was. Yes, we could have left these trees alone. Would their death have been certain, or is it possible experiments in the introduction of natural predators would have progressed enough in time to save them? If not, does it matter that these four trees, out of the hundreds near us,survive? I don’t know. We weighed the options and we made this choice. I wish us all luck.


Last of the Spring Bad Actors-Garlic Mustard!

Alliaria petiolata (garlis mustard) bud

Garlic mustard seedlings

Garlic mustard (Alliaria petiolata) is a biennial, appearing as a rosette of leaves it’s first year and flowering its second. An easy test is to crush the leaves; garlic mustard will smell like garlic. It appears mostly in disturbed forest edges but is quite capable of spreading thickly and becoming dominate in the forest understory. Like other invasives, it has the triple whammy of an early spring appearance, few native enemies and lots and lots and lots of seeds.Around here, we find it follows the flow of water. After a flood or major rain event, you’ll find batches of seeds sprouting where they were dropped.

Generally we have hand pulled, and you’ll often find “garlic mustard pull” events organized by your neighborhood conservation organization. Since they are biennial, chopping off the flower heads with a weed eater before they go to seed is another option we have tried. The seeds remain viable in the seed bank for up to five years, so you have to keep at it.

You’ll read lots of terrifying descriptions of the impact of garlic mustard in the woods: According to the NYS Invasive Species website,  garlic mustard is “…one of the worst invaders of forests in the American Northeast and Midwest…recent findings have shown that garlic mustard has the ability to establish and spread even in pristine areas. This spread has allowed it to become the dominant plant in the undergrowth of some forests, greatly reducing the diversity of all species. ”

HOWEVER, I have read (and heard) from several folks involved with Cornell Botanic Gardens natural areas that they no longer pull garlic mustard as a general rule. This is so interesting to me, I am going to quote here an entire article on why not I gleaned from the NYSFOA newsletter. Enjoy!

NYFOA Southern Fingerlakes Chapter
May 2018

Garlic mustard management update
Dr. Bernd Blossey, Cornell University,
Ithaca, NY 14853, (bb22@cornell.edu)
Background: Garlic mustard (Alliaria
petiolata) was once considered one of the most
problematic plant invaders in eastern temperate
forests. Declines in native plant species diversity and
deterioration in general forest health were attributed
to advancing garlic mustard. The lack of success in
controlling the species resulted in the initiation of
research todevelop a biological control program.
While ecological investigations were pursued,
chemical, and often physicalremoval programs
continued (including “garlic mustard challenges”). At
the same time researchers established longterm
permanent monitoring plots in preparation for
potential insect releases. In these plots the abundance
ofseedlings, rosettes and adult stems, stem height,
reproductive output and herbivory were recorded.
New Evidence
Monitoring of garlic mustard at
many sites across the Northeast and Midwest in these
permanent plots has shown that over time adult
density, rosette density, stem height and the number
of siliques is greatly reduced to an extentwhere garlic
mustard, while present, is reduced to extremely low
abundance. These results occur at all sites.
Additional work using soil sterilization has shown
that these effects are, most likely, explained by
negative soilfeedback, i.e. the build-up of soil
microbial communities that selectively suppress
garlic mustard (other plant speciesappear unaffected).
We are currently preparing these results with our
collaborators for publication in the peerreviewed
literature.Recommendations We are aware that many
organizations and communities are gearing up for
another season of garlic mustard removal,often
dubbed “garlic mustard challenges”. The most recent
ecological work has shown that effects attributed to
garlic mustard invasion are more likely effects of
invasive earthworms and abundant native white-
tailed deer. Garlic mustard will only be able to invade
and establish populations in areas, which have been
colonized by earthworms.Removing garlic mustard
will not help to restore thriving native communities.
In fact, removing garlic mustard will set back the
“self-inflicted” population declines by preventing
negative soil feedback. Only in places where garlic
mustard is not controlled will the species decline
rapidly (often within 5-10 years after initial invasion,
but moreobservations are needed). We recommend
stopping all active garlic mustard removal (unless
initial invasions can bestopped by removing a few
individuals away from well-established populations)
and instead focusing on plantingnative species.
Native species will need to be protected from deer
herbivory behind fences or in cages until deer
populations are sufficiently reduced. Please be aware
that garlic mustard will continue to spread to areas
where thespecies has not occurred previously. The
decline in population and vigor is a function of
residence time.