Southwest Michigan field crop pest and crop report

Some MSU recommendations for your consideration in starting this cool field season.


The late winter and early spring have been colder and somewhat drier than normal, with surface water resources a bit lower than we saw going into the same period in 2010. We are way ahead of the curve in terms of primary tillage because of the great conditions last fall. Winter annual weed pressure varies greatly between fields. The 80-plus degrees temperatures on April 10 really kicked winter annual weed growth into high gear. The six to ten day outlook for the southwest region calls for a changing pattern, with much above normal temperatures and precipitation for the region. Of course there is the possibility of measurable snow in the near term forecast. The 8-14 day outlook predicts moderating temperatures but keeps the area in the above average in precipitation zone, which may mean a soggy and muddy start for the early planting window. Precipitation totals from around the region over the last 4 weeks (since 03/18/2011) are Allegan 2.46” (-0.02), Benton Harbor 2.27” (-0.21), Coldwater 2.02” (-0.27), Holland 3.45 (+0.97), Three Rivers (2.53 (+0.24). We generally do not start worrying about Base 50 GDD’s until after the crops are planted, but the Base 41 GDD’s that we use to track alfalfa development across the region are 152 for Kalamazoo, 171 for Holland, 133 for Coldwater.

Corn and soybean pests

While it is a bit early to worry about pests for these crops in the field, we should be keeping an eye on the winter annual weed growth. Not only do these weeds create problems for tillage and planting operations, some of the species can potentially serve as a food source for soybean cyst nematodes and white grubs, and provide an attractive location for black cutworm moths to lay eggs. A quick tillage or burndown herbicide application can sometime be beneficial to keep these weeds at bay, especially if the field will not be able to be tilled or planted for an extended period of time. For more information on MSU’s Recommendations on burndown herbicide programs for corn and soybeans, go to the 2011 MSUE E-434 Bulletin, Weed Control Guide for Field Crops. Recommendations for burndown programs can be found in the Corn and Soybean Sections of this guide.

Soybean Sudden Death Syndrome infected fields

Several fields in southwest Michigan showed symptoms of Sudden Death Syndrome in 2010. The fungal pathogen that causes SDS, Fusarium virguliforme, is not considered to be controlled by crop rotation. If you are going to plant soybeans in a field that showed SDS symptoms in 2010, look at your seed company’s more detailed data and choose to grow varieties that show the most tolerance to SDS. Research near Decatur last summer showed that a least one variety with a dual source of SCN Resistance (PI 548402 x PI 88788) exhibited good tolerance to the disease. It would also be a good idea to sample for Soybean Cyst Nematodes, as SDS is commonly associated with high levels of SCN in fields, particularly on sandy soils.

Soybean seedling diseases

MSU generally does not recommend planting soybeans after soybeans because of disease concerns. If you are planning on planting soybeans without rotation, consider using a fungicide seed treatment on soybean fields that were planted to soybeans in 2010. It can also help when planting soybeans into cool, wet soils. This is especially important if you saw seedling mortality from Rhizoctonia or Pythium in the previous year(s). Pythium and Rhizoctonia are different types of fungal pathogens, and so if you are not sure which disease organism caused the challenge in the field, use seeds treated with a broad spectrum fungicide package that control both the water molds and Rhizoctonia and other soil fungi.

Wheat really began to green up, especially following the temperatures in the mid-80’s on April 10. Nitrogen fertilizer applications have been going on. The crop generally looks to have survived the winter in good shape.

Alfalfa has broken dormancy and has been growing with the warmer weather. Alfalfa weevil development models use degree-day accumulations (base 48 F) beginning January 1. Adults can often be found when temperatures are above 48°F feeding and laying eggs in the fields, particularly in sunny and wind protected portions of fields. Egg hatch is expected beginning at 300 DD and small larvae (1st and 2nd are expected to feed between 301 and 438 GDD’s, producing light leaf feeding. Major leaf feeding generally occurs as larvae grow and is expected when 3rd and 4th instars feed (between 439 and 595 GDD). You can follow the predicted development in your area by clicking on your nearest Enviro-Weather Station and clicking on the Field Crops tab of the website. This provides a guide of when to scout for the pest, and when to cut alfalfa hay for optimal quality for dairy producers.

We have had several questions about controlling Hoary Alyssum in hay fields this winter. This weed is of particular concern because of the species toxicity to horses. MSU has an excellent publication E-2987 outlining identification of the plant, the life cycle and herbicide options that can be used for control in alfalfa.

New invasive weed species alert for St. Joseph County

An aggressive new species of the pigweed family,Palmer Amaranth, was found in St. Joseph County in 2010. More information will follow shortly from Dr. Christy Sprague, MSUE Field Crops Weed Control Specialist and Dan Rajzer, MSU Field Crops Weed Control Educator.

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