In this issue
§ Asian soybean rust sentinel plot scouting report: August 18-24
§ Herbicide resistance screening available at MSU Diagnostic Services
§ Preharvest treatments in dry edible beans
§ Stalk nitrate test and N management for corn
§ Potato late blight open day – September 1
§ MSU adds new soil fertility and nutrient management expert
§ Regional reports
§ Weather news
Twelve reports were filed from the 20 soybean sentinel plots during the reporting week.
No soybean rust has
been found on soybeans or other plants in
Growth stage: One plot is at R5, nine plots are at R6 and two plots are at R7. Lower leaves are beginning to yellow and the leaf canopy is noticeably thinner in some plots.
Plant height: Ranged from 24 to 40 inches. Ten plots are in the 36- to 40-inch range.
Degree of canopy closure: Ranged from 84 to 100 percent.
Soybean diseases present: Three-fourths of the plots report multiple diseases ranging from one to seven diseases per plot. Low levels of Septoria brown spot, low to high levels of downy mildew and low levels of bacterial blight are the most common diseases. Also noted were powdery mildew, Phytophthora stem canker, sudden death syndrome, white mold and soybean cyst nematode.
Insects present: Soybean aphid levels are dropping in fields that haven't been sprayed. The highest count came from two plots, each reporting about 100 aphids per plant. Japanese beetles, Western corn rootworm and spider mites, all at low levels, were also reported.
Sugar beet: Rhizomania (BNYVV), Rhizoctonia
Soybean: Soybean cyst nematode
Soybean rust continues to spread slowly within
Several weed species have developed resistance to popular
herbicides used in
Confirming herbicide-resistant weeds in
The next several weeks prior to harvest are perfect for collecting mature, high quality weed seed. Select plants 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 plants or seed in plastic!
Fees associated with herbicide-resistant weed testing are
generally $50 per sample per herbicide site of action (ie:
ACCase inhibitors, ALS inhibitors, Photosynthesis
inhibitors). Two exceptions to this fee are horseweed (a.k.a. marestail, Conyza canadensis) and common lambsquarters
(Chenopodium album) collected from
Please contact Steven Gower (517-432-9693, sgower@msu.edu) with any questions regarding sample collection. Send samples to:
MSU Diagnostic Services
Attn: Steven Gower
101 Center for Integrated Plant
Systems
Common lambsquarters, pigweeds and common ragweed have plagued many dry bean fields this summer. With harvest quickly approaching, preharvest treatments may be useful in helping to reduce harvest issues that can occur when these weeds are green and luscious. Currently, two different preharvest herbicide options are available to help control these and other weeds that hinder harvest in dry edible beans. These options are glyphosate (three Roundup brand products – Roundup WeatherMax at 22 fl oz/A, Roundup UltraMax at 26 fl oz/A, and Roundup OriginalMax at 22 fl oz/A) and paraquat (Gramoxone Max at 1.3 pt/A). Even though both of these herbicides are labeled as preharvest treatments in dry edible beans there are some different precautions and use patterns for these herbicides.
Applications of glyphosate are intended to be used to control weeds that may hinder harvest. Glyphosate products should be applied with 17 lb/100 gal of ammonium sulfate (AMS). Do not use glyphosate products for vine dessication, as residues of glyphosate have been found in harvested beans if applications are made too early. For preharvest purposes only, glyphosate should be applied when beans are in the hard dough stage (30% moisture or less). Applications of glyphosate should also be made seven days before harvest and only one application should be made per year. Do not apply glyphosate to beans grown for seed and do not feed treated vines and hay from these crops to livestock. If a vine desiccation treatment is needed paraquat (Gramoxone Max) should be used.
Apply Gramoxone Max with 0.25% v/v of a non-ionic surfactant. Gramoxone Max should be applied when the dry bean crop is mature; at least 80% of the pods are yellowing and mostly ripe and no more than 40% (bush-type beans) or 30% (vine-type beans) of the leaves still green. Applications should be made in at least 20 to 40 gal/A of water. If growth is lush and vigorous a split application of 0.65 pt/A followed by 0.65 pt/A may provide better coverage and control (do not exceed 1.3 pt/A). Do not harvest dry beans within seven days of application.
The nitrate N concentration in the lower portion of the corn stalk at the time grain black layer is formed is a good indicator of the nitrogen status the crop experienced throughout the growing season. When used over a number of years the stalk nitrate test can help identify N efficient fields or management systems, thus enabling fine tuning of N inputs.
As corn approaches maturity, plants stressed for N will move
nitrate from the lower cornstalk to the ear resulting in a low stalk nitrate
concentration. When corn plants have sufficient N or more than sufficient N for
maximum yield, nitrate accumulates in the corn stalk. Extensive studies done by
Purdue and
|
Excessive |
> 2000 ppm. |
Excessive N available to the crop,
or some other production factor limited crop growth and yield. |
|
Optimum |
450 to 2000 ppm
(Purdue) |
Grain yield was not limited by
amount of N available to the crop. |
|
|
700 to 2000 ppm
(ISU) |
|
|
Marginal |
250 to 700 ppm
(ISU) |
Nitrogen supply may have limited
yield. |
|
Low |
< 450 ppm
(Purdue) |
N was likely yield limiting during
the growing season, especially < 250. |
|
|
< 250 ppm
(ISU) |
Both sets of studies show that a stalk nitrate N
concentration above 2000 ppm is indicative of
excessive nitrogen having been available to the corn crop. Quite often this is
associated with the application of animal manure, but may also be related to
over application of fertilizer N. In the Purdue studies maximum yields were
associated with stalk nitrate N concentrations above 450 ppm.
The optimum time is one to three weeks after black layer has formed in 80 percent of the corn kernels. Cut an eight inch segment of the stalk, between six and 14 inches above the ground, from 15 stalks within the area of interest. Remove any portions of leaves that may remain attached. Splitting the stalk segments will facilitate drying. Refrigerate the stalk segments if the sample cannot be sent or delivered to a test lab within one day. Do not use plastic bags as this will prevent drying and may cause spoilage. The testing lab will oven dry and grind the stalks prior to analysis. This service is provided by the MSU Soil and Plant Nutrient Lab and other private labs.
In N rate studies conducted at MSU in 2003 and 2004, the stalk nitrate N concentration reflected the corn grain yield response and the excess N application according to the guidelines presented in Table 1. The total N concentration of the ear leaf at silking and the corn grain showed when the N rate was too low, but did not reflect when excess N was applied. Hence, the stalk nitrate test is a better diagnostic tool. Even though it is post-mortem it can be useful for long term adjustment of N management practices. Farmers are encouraged to try this test on a few fields with different N management practices. It can tell a lot about how N is being utilized by a corn crop. Over a few years one can develop a good data base for evaluating the appropriateness of various N management practices.
The annual late blight open day at the MSU Muck Farm in
Lunch is from
Welcome to Ron Gehl, new soil
fertility and nutrient management faculty member in the Crop and Soil Sciences
Department. Ron completed his PhD and a one-year post-doc at
Scattered rain showers
over the past two weeks have yielded variable amounts of rain across the
region. Crop damage from dry weather this season is still evident in the
western parts of the region. Much of
Corn
maturity is progressing rapidly. Some fields are at dent stage, most are late
milk. Second generation European corn borer moth numbers in pheromone traps
have peaked.
Dry bean harvest is underway with early light red kidney beans and cranberry beans.
Almost all beans are turning. White mold is evident in several fields.
Soybean aphid is hard to find in many soybean fields. A few fields are starting
to turn.
Early indications suggest
that we may have very good yields of sugar
beets in many areas of
The region received scattered showers over the past two weeks. Some parts of the region received over one inch of rain while others got little or nothing. It seems that this summer some areas got very timely rains while others got very little. For the most part, soil moisture is adequate at this time to complete most crops.
The corn crop is denting. There are farmers that are beginning to open fields chopping corn silage. We expect harvest to begin next week. The area has had record GDD, and with early planting, harvest will be early this year. Growers that will be harvesting corn silage are advised to start getting whole plant moisture tests so corn will not get to mature for quality silage. We are still catching corn borer moths in the traps. The yield potential looks very good at this time.
Soybean aphid populations are declining rapidly. The numbers of beneficial insects are climbing and are aiding in the decline of aphids. At this point in the growing season many of the early planted beans that are late group I will be starting to turn over the next few weeks. We are seeing white mold in several fields. Yield potential looks very good.
Harvest of third cutting alfalfa is nearly complete. Many are reporting very good yields, but scattered rains are making quality an issue for growers trying to get hay dry. Many growers are reporting that the second and third cutting yields are more than making up for a small first cutting. Summer seedings are being made at this time.
Field preparations are being made for planting wheat.
Dry bean fields are turning and harvest is just getting under way. It is still too early to get a handle on yield.
A break from high temperatures has been noticed in the past week. This is welcome to the areas with limited moisture. Soil moisture is getting very low and causing some crop stress symptoms, especially in lighter soils.
Regrowth of alfalfa is slow due to limited moisture, but there have been plenty of days for baling and chopping of late third cutting.
The good sugar beet fields continue to look good but are not far away from moisture stress. Weeds and cercospera leafspot are the challenges to this crop. Many fields have been either rope wicked or weeds chopped to get some handle on heavy infestations. The lower temperatures are giving some help to slow leafspot infection.
Dented kernels of corn are easy to find in most fields with maturity being at a good point for this date. Corn silage harvest has begun with good yields.
The soybean crop has taken this late season drought a little tougher than other crops. It is now easy to find problems such as white mold, downy mildew, brown spot, spider mites and soybean cyst nematode damage. Natural senescence is causing some change in plant color in early planted fields. Soybean aphids have dropped off in populations but are still around in many fields. The advanced growth stage of R6 is beyond most management practices to affect yield.
Dry bean harvest has begun. Early planted and maturing beans are being harvested while later planted beans are still very green. Yields are variable as growing conditions have been throughout the year.
High pressure centered over southern
Further ahead, latest medium-range forecast guidance
suggests upper air troughing across western