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FREE screening for
herbicide resistant marestail in soybean production systems
Steve Gower
Diagnostic Services
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Marestail (Conyza
canadensis) has become a troublesome weed in many parts of the
Eastern U.S. in recent years due primarily to the development of
herbicide resistant populations. Glyphosate-resistant marestial
has been confirmed in several states including: Delaware,
Maryland, New Jersey, Tennessee, Kentucky, Missouri, Ohio, Indiana,
Mississippi, and Arizona. ALS-resistant marestail has been confirmed
in Ohio and was just confirmed earlier this year in Michigan in
Branch, Eaton, and Sanilac Counties.
A mature
marestail plant can produce thousands of wind-disseminated seed
- seed that is capable of blowing considerable distances only to
infect new fields if resistant. Because glyphosate and ALS-inhibiting
herbicides are very important to Michigan soybean growers, it is
essential to identify herbicide resistant populations and employ
proper management strategies.
For these reasons, marestail
populations will again be screened for glyphosate and ALS resistance
this fall in Diagnostic Services. This
service is FREE. The Michigan Soybean Promotion Committee will
cover all sample costs.
If you have fields where marestail is a problem
and resistance is suspected, collect seedheads from mature plants
in late summer to early fall. Consult the marestail submittal form
for detailed sampling instructions on field criteria and seedhead
collection. Marestail submittal forms will be available at various
locations, including county MSU Extension offices, grain elevators,
and chemical retail businesses. Marestail seedheads and the submittal
form should be dropped off at your local county MSU Extension office
or send directly to:
Diagnostic Services
101 Center for Integrated Plant Systems
East Lansing, MI 48824
Attn: Steven Gower
If you have any questions, please call Steve Gower
at 517-432-9693 or send an email to sgower@msu.edu
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Confirming herbicide resistance
in weeds
Steve Gower
Diagnostic Services
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Herbicide-resistant weed species have been documented
throughout Michigan. There are currently 11 weed biotypes resistant
to one or more herbicides in the state. If you suspect resistance
in any weed species and would like to confirm this, seedheads can
be collected upon maturity and submitted to MSU Diagnostic Services
for a herbicide resistance
screen.
The next several weeks prior to harvest are perfect
for collecting mature, viable weed seed. Select plants that were
definitely sprayed (not along field edges or sprayer skips). Harvest
seedheads by cutting the stem just below the seedhead. Place seedheads
into a brown paper bag or collect seed in a small envelope or container.
Never seal plant or seed in plastic!
Fees associated with herbicide resistant weed testing
are generally $20 to $30 per sample (a sample could be a composite
sample of one field). Please contact Steven Gower (517-432-9693,
sgower@msu.edu) with any questions regarding sample collection.
Send samples to:
Diagnostic Services
101 Center for Integrated Plant Systems
East Lansing, MI 48824-1311
Attn: Steven Gower
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Regional
reports
1
- Southeast
Ned Birkey
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Weather
The weather has been good for tourists and parades. The
average August temperature so far in Toledo has been 80 compared
to the normal 86 degrees. Precipitation has been coming regularly
so that the corn plants have no firing of lower leaves. However,
we have missed most of the major storms this summer, though even
Lenawee and other nearby counties have not.
Commodity reports
Alfalfa third cutting is underway. Putting up
quality hay this summer is a challenge, but the second and third
cuttings are very good. Potato leafhoppers are not as abundant now
as during the second cutting crop.
Corn is in the milk to dough stage with
many plants putting on a second ear. Most fields have green leaves
throughout the plant. Hail or high winds are about the only things
that can adversely affect this big crop. European corn borer numbers
at the Monroe County sweet corn site show increasing numbers, with
trap counts of 33, 34 and 248 this week, up from 5, 32 and 138 last
week
Soybeans are not out-of-the-woods yet. Soybean
aphids, white mold, soybean cyst nematodes, sudden death syndrome,
Phytophthora root rot and spider mites are all problems facing this
crop. Many fields have had tremendous growth in the month of August,
though some fields are now past flowering and into pod fill.
Tremendous spraying for soybean aphids is going
on, though there are many dead aphids and carcasses in some fields
and some farmers are deciding against spraying, especially if they
cannot get someone in to do this or their boom is too small and
they fear yield losses from driving through fields more than aphid
yield loss.
Some fields are very clean of weeds while others
will have big problems. Growth and maturity is variable, with one
early-planted field of 3.2 maturity appears to be finished flowering
while another field of 2.0 maturity is taller and greener. Many
fields have lower leaves turning.
Wheat harvest was a potential record acreage
and yield, and prospects are good for high wheat acreage again this
fall. Many farmers are working wheat stubble with deep tillage tools
or spraying or mowing for weed control.
Miscellaneous
It appears as if we may have a record corn crop, though
soybeans have almost as many problems as the Tigers.
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2
- Southwest
Mike Staton
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Weather
Most areas have not received significant rainfall in
three to four weeks. High temperatures and high humidity have prevailed
over the past week.
Commodity reports
Even the late-planted corn has completed pollination.
Some fields have been showing signs of moisture stress for the past
week. High populations of rootworm beetles are present in many fields.
The stalks in some areas are goose-necked due to severe rootworm feeding
this summer.
Most soybean fields have begun filling pods.
Moisture stress has been evident in most fields for the past week.
The warm, humid weather has caused soybean aphid populations to
decline dramatically over the past week. Western corn rootworms
can be found in many soybean fields where they will lay their eggs.
The eggs will hatch next summer and the larvae will be present to
feed on first-year corn roots.
Alfalfa fields are growing slowly due to
the lack of moisture. Potato leafhopper populations are declining.
However, growers should continue to monitor population levels and
treat if warranted.
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3
- West Central
Fred Springborn
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Weather
It is hard to make general statements about weather or
crops this year. Variable seems to be the only word that really
fits. Rainfall in Montcalm County continues to be quite variable,
much of the county is quite dry. High temperatures have been holding
in the mid- to upper 80s. Low temperatures have been in the mid-50s
to lower 60s. While warmth and sunshine have been very welcome due
to the slow progress of many crops, we could use a bit of rain.
Commodity reports
Potato leafhopper is still a threat to alfalfa.
Oats harvest
is complete for the most part. Yields were not outstanding ranging
by and large from 40 to 90 bushels per acre.
In corn, pollination
has occurred in virtually all fields. Most of the crop is in blister
to milk stage. European corn borer numbers caught in pheromone traps
continue to be quite low, except in one location (Trufant) where
numbers are increasing rapidly.
Soybeans are
forming pods. Soybean aphid has been observed in high numbers in
many fields. The natural predators have also been observed in high
numbers in many of these fields in both Montcalm and Newago counties.
Dry beans are
progressing well. Overall, many fields of cranberry beans
are turning. Fields need to be monitored and scouted closely for
European corn borer, potato leafhopper and Mexican bean leaf beetle.
In sugar beets,
monitor fields closely for Cercospora leafspot. Weather conditions
have been favorable for development of this disease. Other disease
problems have been Rhizoctonia root rot (particularly where PIK
beets had been in previous years), tarnished plant bug and herbicide
injury. Careful attention should be paid to what the rotation restrictions
are on herbicides applied to other crops in fields that will rotate
to sugar beets in future years.
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4
- Central
Paul Gross
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Weather
The region has received very little rain over the past
weeks. When rains came they were very spotty so there is some real
variability in crop conditions across the region. Many areas are
in need of rain soon or yields will be greatly reduced.
Commodity reports
Corn is ten days to two weeks behind normal. We
will be in need of a long warm fall to complete the crop. There
are some areas that the corn is drying up and will be chopped for
silage while other areas will have record yields barring an early
frost. Corn borer pressure has been light.
Soybeans range from very good to poor in
areas that need rain. The big story is soybean aphid. Many growers
are spraying for this pest. This decision is being based on growth
stage. Once the plant has flowered, most spraying will be less effective.
The fungus that kills the aphids has been found in several fields.
Weather conditions are ideal for the fungus to continue to reduce
the aphid populations. White mold has been reported in several areas.
Many growers are very concerned that mold will significantly reduce
yields.
Wheat harvest is complete. Most yields were
very good considering some of the late plantings and problems this
winter and spring.
Oat and barley harvest is nearly
complete. Yields and quality have been excellent.
Harvest of third cutting alfalfa is well
under way. Yields have been reduced due to dry conditions and leafhoppers.
Sugar beets need rain. Leafspot is present
in most fields and many are treating.
Dry beans are beginning to turn - harvest
will be right around the corner. Some mold problems have been reported.
Leafhopper pressure has been high.
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5
- Thumb
Mark Seamon
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Weather
Recent weather is causing some crop stress due to limited
rainfall and some high temperatures. Sandy soils are showing the
most stress symptoms. This plant stress is creating an opportunity
for many other crop problems to show up.
Commodity reports
Regrowth of alfalfa has slowed due to dryer conditions.
Sugar beet growers are doing an excellent
job this year in controlling Cercospera leafspot. Many growers have
made a second application of fungicide. A few weeds have poked through
the crop canopy in the past two weeks. Dry soil conditions have
many fields showing some yellowing. Ligus bugs are also causing
some yellowing of leaf tips. A few problem areas are showing up
with Rhizoctonia and sugar beet cyst nematode being the main culprits.
The corn crop continues to look good. Limited
soil moisture is getting to be a concern with kernel fill. Good
conditions up to this point have created good yield potential but
we will need more moisture and heat to get this crop mature.
Many dry bean fields are showing maturity
with some color change. Some are maturing uneven due to earlier
water damage. It doesn't look like there will be much early harvest
of this crop.
Mold, aphids and soybean cyst nematode
Soybeans are the crop that has taken the biggest
hit in the past two weeks. Several problems are showing up. White
mold is easy to find in many fields. Some have large areas that
are being consumed while others have occasional plants that can
be found infected under the crop canopy. Soybean cyst nematodes
(SCN) are also taking a toll. The dry areas have exaggerated the
symptoms of the nematode feeding. SCN resistant varieties are showing
significant visual differences. Soybean aphids continue to reproduce
to levels over the threshold. Many soybean growers have questions
of whether to treat a field that has few blossoms. A few fields
are being treated with a second application of insecticide to control
the aphids. Some fields have thousands of aphids per plant with
high levels of honeydew. Sanilac County is treating many late-planted
fields that are actively flowering.
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6
- Northern Lower Peninsula
Dave Glenn
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Weather
Hot, dry weather continues with no significant rain in
over a month. Temperatures the past week have hovered in the 80's
to low 90's. Soil conditions are extremely dry as we now have had
five years of a running drought!
Commodity reports
Wheat is all harvested with yields from 45 to
85 bu/acre. Test weights have all been pretty good with no sprouting.
Harvest ran about two to three weeks late this year.
Soybeans are
suffering with the heat and lack of moisture. Many fields are wilting
in patches and sandier parts of fields. Pod set seems to be light
this year in most fields with seed still pretty small. We have a
long way to go to get seed filled out and moisture is the limiting
factor. Soybean aphids are in every field. About half of the fields
are being sprayed with Asana having mediocre kill. Numbers seem
to be on the decline with some fungus present, but not enough yet.
Yields will be down due to drought and aphids. Good plant growth
and height, but sparse pod set.
Corn looks excellent
this year. Plants are very tall and as green and healthy as we've
had in years. Ears are average with many smaller ears and a few
fields with larger ears. Expectations are 100 bushel corn this year.
Corn borer is present in most fields.
Alfalfa - what is that? With the
dry weather, we have had tremendously low yields this year. Third
cutting will be non-existent in most cases with second cutting about
50 percent of normal. Quality has been OK due to lack of rain!
Dry beans are
suffering from the drought. Many fields are turning yellow already,
which is two to three weeks too early since beans were planted late.
Bean beetles have dessimated a few fields.
Oats are partially
harvested with the rest coming off in the next week. Some oat yields
have been excellent with 100 or more bushels per acre.
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Weather
news
Jeff Andresen
Agricultural Meteorology
Geography
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A pair of upper air disturbances will move from
west to east along the US/Canadian border during the upcoming week,
setting the stage for at least two opportunities for rainfall. The
first disturbance, accompanied by a surface cool front, will pass
through the state Thursday (August 21) into early Friday with scattered
showers and thunderstorms spreading from southern sections by late
Thursday. Dew point and air temperatures ahead of the cool front
will reach the mid 70s and low to mid 90s respectively in southern
sections of the state, leading to some of the hottest (and for humans
and livestock, the most uncomfortable and stressful) conditions
of the growing season thus far. Given the high instability associated
with the hot, humid weather on Thursday, some thunderstorms may
be severe, with the primary threat coming from high winds and isolated
large hail. All precipitation will end from northwest to southeast
across the state by early Friday, setting the stage for a cooler,
dry weekend. Look for temperatures to fall back to highs in the
70s and lows in the 50s by Saturday and continue into Monday. Low
temperatures may dip back into the 40s Saturday morning in some
inland locations. Warmer weather is expected by the beginning of
next week, along with the next chance for rainfall to the state
by late Monday or Tuesday.
Looking further ahead, latest medium-range forecast
guidance is once again forecasting a return of the very persistent
pattern of this summer season: a broad upper air ridge over the
western US, with troughing across the east. As a result, both the
6-10 and 8-14 day outlooks, covering August 26-30 and August 28
through September 3 respectively, call for below normal precipitation
statewide. Lack of available soil moisture has become a problem
in some sections of the state missed by recent rainfall. Some areas
have not had significant rainfall since early July. The forecast
also calls for near normal temperatures during the 6-10 day time
frame and for below normal temperatures during the 8-14 day period.
This is also a concern, as current seasonal growing degree day deficits
and delayed crop phenological development persist across most of
the state (most pronounced in central sections of the Lower Peninsula,
where totals lag the normals by as much as two weeks).
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