I'm Ron Patterson with Utah State University Extension in Weber and Morgan
counties. Weeds do not recognize property boundaries, and really are everybody's
problem. Today's Weed Warrior topic is white top, or hoary cress. White top is a
creeping perennial in the mustard family. Because it is a creeping, spreading
perennial, white top grows in dense clusters and it's really quite easy to
recognize in the spring especially when it's in bloom. White top will germinate
in the summer and spring and then it sends down that taproot. It goes down
about 12 inches in about 30 days. After about 21 days they'll start sending out
runners or rhizomes, and you can see from this view here that
you'll have several plants come up from rhizomes. Now these rhizomes, which are
actually underground stems or a modified stem - some people call it a horizontal
root - but it's actually a stem, and you can see that it will send up shoots
along here, and if you end up cutting up that stem in your mechanical removal
efforts you'll get new plants come from those split up rhizome. Notice that the
leaf color of white top is kind of a gray-green and these basal leaves have a
petiole down to the stem. On the other hand the leaves that are on the flower
stock, while still that gray-green color, are actually clasping they come right
down to that flower stock. The flowers of white top are white, which makes sense,
they have four petals, and then there's this cluster of them - kind of a flat top
cluster. As with all weed problems that we have prevention is the best cure, so
if we can keep these from getting into our place that's great. So clean your
equipment: your farm, construction, ATV equipment, where you've been operating
from and be very careful of where you're getting soil from. You see a lot of piles
of soil that have white top on them, those typically had the roots
of the rhizomes come in with that pile of soil so that it then takes place, sets
up its clonal colony, it starts to spread the seed. Weed-free hay is a very
important part of weed prevention: be sure the hay has been cut
before the weeds have gone to seed. Good pasture management is really important
with weed control: you want to have the good plants competing with the weeds so
that they will do better. You spray down your weeds, but if you don't have good
plants taking up there they'll - the weeds will come right back. So don't over
graze your pastures; graze them properly, manage them properly, and that will help a
lot with your weed control efforts. White top has no biological controls - at least
from the insects and disease point of view - but sheep and goats will graze it.
The problem with that is they'll usually graze the more desirable plants first,
and then they'll go to the white top so that just gives the white top a competitive
advantage. Probably not the best way to go with with using sheep and goats to
graze your white top. So because white top spreads mostly by
rhizomes, using a shovel or a tiller or or cultivation equipment is not really
the best way to control it. But you can do it, if you do that for three or four
years and you make sure you pull up all the roots. You have to do it on a regular
basis, about every ten days, in order for it to be effective. So if you've got the
time and you don't have a very big plot, you can dig it up and take care of it
with the mechanical removal. Although white top does spread mostly by rhizomes
it also does spread by seed. The seeds are fairly short-lived maybe five...five
to seven years in the nature, but in the lab about five years is what they've
been able to get the seed to survive. The most common way for seed to spread is to
get down into the water coming down here with rainfall or whatever; down into the
irrigation ditches, and rivers, and streams. And so trying to keep the white
top and the other weeds away from the river and streams will help a lot in
prevention. The main keys then to controlling white top is to stop the
seed production - which you can do by mowing - but you also need to kill the
roots, which you can't do by mowing. You need to get those roots killed and so
herbicide is usually the best way to do that. If you're non-herbicide control
options are not going to work for you there are some broadleaf weed controls
that can work; there's 2 4D, Telar, and Escort. Telar is Chlorsulfuron,
Escort is Metsulfuron. 2 4D does not have
a lot of soil activity, so it will not control the germinating seeds, but it
does work on the smaller seedlings and the rosette stage of the white top. Telar
and Escort both have good soil activities, so it will control the
germinating seedlings as well as when you get into this bud stage. Telar is
really good in the flowering stage, so at this point when you're in full bloom
Telar is a good product to use and Escort is perhaps not quite so late in
the blooming stage, more of a bud stage, but - but that works quite well. They all
are really quite good in the fall when you're treating the rosette or seedlings,
and then in the springtime - early in the springtime 2 4D - later in the springtime
Telar or Escort would be pretty good options as far as herbicides go. Your non
selective herbicide options are glyphosate or imazapyr, and they will
kill everything in - that you spray. The glyphosate has no soil activity;
glyphosate is like Roundup, or Killzall, or there's several names of with
glyphosate, that's the common chemical name. So glyphosate will kill everything
and imazapyr will also kill everything, but it has soil activity and
so you will have a period of time where you're not going to get any regrowth of
anything coming through there. So the imazapyr is a good non-selective
herbicide, and it's actually labeled on water, but it's not a good option if you
want to be planting back in the area. I'll place some links in the video
description below that will give you more information on herbicide options to
control white top; be sure to always read and follow the label directions. White
top is a serious weed issue in Utah but ignoring it will not make it go away.
Everybody needs to do their part, so be a good neighbor: be a Weed Warrior.