August 21, 2003

In this issue

§      FREE screening for herbicide resistant marestail in soybean production systems
§      Confirming herbicide resistance in weeds
§      Regional reports
§      Weather news

FREE screening for herbicide resistant marestail in soybean production systems
Steve Gower
Diagnostic Services

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

Confirming herbicide resistance in weeds
Steve Gower
Diagnostic Services

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

Regional reports

1 – Southeast
Ned Birkey

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.

2 – Southwest
Mike Staton

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.

3 – West Central
Fred Springborn

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.

4 – Central
Paul Gross

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.

5 – Thumb
Mark Seamon

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.

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.

6 – Northern Lower Peninsula
Dave Glenn

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.

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).