March 2022 - 21

yellow loosestrife, Carolina redroot and
haircap moss.
The researchers collected data on 40
random quadrants per weed species,
including some plots without weeds
present and some with very high weed
densities.
Colquhoun and others took weed
counts, weight of both fresh and dried
biomass and made visual estimates of
weed ground cover within each quadrant.
Data was also gathered on cranberry
fruit quality including yield, berry
color, percent of fruit rot, amount of
insect damage and in some cases total
anthocyanins and brix readings.
In addition to testing their
methodology across a spectrum of weed
species, the collaborators are looking
to see if the relationship between
weed growth and cranberry yields are
consistent from season to season.
The data on dewberry in Wisconsin
from the past two growing seasons
showed that all of the weed growth
parameters measured were good
predictors, but that visual ground cover
estimates alone provided an easy - and
very accurate - prediction of cranberry
yield.
Collaborating on the research with
Colquhoun is Hilary Sandler, director
of the University of Massachusetts
Cranberry Station, East Wareham,
Massachusetts; Katie Ghantous,
Integrated Pest Management weed
scientist at the UMass Cranberry Station
and Thierry Besancon, Extension weed
scientist for specialty crops at the Philip
E. Marucci Center for Blueberry and
Cranberry Research and Extension in
Chatsworth, New Jersey.
In addition to helping develop weed
thresholds, Colquhoun is also running
trials on new herbicides being tested for
use on cranberries.
" As is the case with most of our
pesticide development, the newer
herbicides that are coming along are
targeted, narrower spectrum herbicides.
We currently have four herbicides in the
registration process and they really have
very targeted weed control spectrums, "
Colquhoun said.
Two of the herbicides being tested
are very safe when used on dormant
cranberry vines and give persistent
weed control. But if the applications
were off by just a few days, vines showed
significant damage that persisted
through harvest, Colquhoun said.
Colquhoun also discussed the rapid
advances being made in robotics for
weed control, particularly in Europe.
While costly now, automated weed
control systems may become more
feasible in the future.
Noting that cranberry beds in
Wisconsin tend to be uniform laserleveled
rectangular sections, the use
of robotics may be feasible one day,
Colquhoun said.
" If there is any production system
where I can imagine this working, it's
cranberries because we are already so
precise. This just adds another layer and
mechanizes something that right now
requires significant labor input, " he said.
More than 250 registrants from 10
states and four Canadian provinces
participated in this year's Wisconsin
Cranberry School. Organizers had
planned to hold an in-person event this
year, but due to a surge in COVID-19
cases when conference plans were being
finalized, the decision was made to
change to a virtual event. FGN
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Wisconsin cranberry grower Jack Potter
uses pliers to try to pull a seedling maple
tree.
" We don't have to weigh anything. You
don't even have to count plants. You can
just throw down a quadrant and estimate
the percent cover and we can use that
to predict yield loss compared to where
there is no dewberry. It's a very simple
approach to at least get an estimate of
what you're dealing with, " Colquhoun
said.
Studies in New Jersey on Carolina
redroot found insect damaged fruit had
a strong relationship with weed density.
Colquhoun suspects Carolina redroot
might be a host of some of the insect pests
that damage cranberries.
" This offers us another reason why we
need new tools to control problematic
species like Carolina redroot, " he said.
Preliminary results from studies
in Massachusetts on whether haircap
moss has an impact on yield were less
consistent, Colquhoun said.
" We're collecting data because this
hadn't been done extensively before. As
a matter of fact in the literature there is
only a single paper on weed impacts on
cranberries conducted by (University
of Washington Extension Professor
Emeritus) Kim Patton and his group in
1994, " Colquhoun said.
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March 2022

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