Southwest Michigan field crop regional report – April 17, 2015

Field preparation work is progressing in southwest Michigan and winter annual weeds are off to a really slow start.

Spring has come slowly to the “Banana Belt” of Michigan, but it has arrived as of last week, so no one is really complaining too loudly. However, the old adage “it is later than you think” will be the case for most producers as we head to the fields. Field preparation work – field cleanup, early fertilizer applications of potash – is progressing quite well.

We have been a bit wetter than the rest of the state, so tillage operations are behind normal quite significantly. Depending on your soil type and ability to break up clods, it might be better to wait for a little drier conditions to start field work in earnest. The best news is that winter annual weeds are off to a really slow start, so that should help to take off the pressure on delayed primary and secondary tillage operations.

Weather

Precipitation levels are somewhat behind normal across much of the state, especially the southwest region. The wetter than normal soils are primarily being caused by the cooler than normal temperatures in March and late snow cover. Rainfall is running between 0.75 to 1 inch behind normal over the last four weeks, and about 0.5 inches over the last week.

Growing degree days (GDD) are not really that relevant yet except for alfalfa. Alfalfa GDD base 41 averaged 163 from March 1, and ranged from 199 in Berrien Springs, Michigan to 112 in Fennville, Michigan.

Crops

Alfalfa has broken dormancy for about 1.5 weeks now and is greening up nicely. There is little evidence of winter damage to seedings and established stands I have walked. Alfalfa weevil overwintering adults should be actively feeding now in more protected areas of fields and those with exposed southern slopes. These adults will begin laying eggs in fields. Female weevils lay eggs in stems. Egg hatch occurs at around 300 GDD base 48 from Jan. 1. Based on the base 41 temperatures shown above, it should be awhile before the larvae hatch. Watch for pinhole feeding up near the top of the plant when the larvae do hatch.

Wheat stands seem to have greened up quite nicely, although fields that are near our office in Paw Paw, Michigan were planted fairly early given the weather last fall. Winter annual weed growth remains behind normal, but growers should monitor their fields to make weed control decisions.

Early-season insects to watch out for

Corn flea beetles should have seen colder than normal conditions, which normally reduces worry for them as seed corn pests and carriers for the Stewart’s wilt bacteria. However, we had exceptional snow cover over most of southwest Michigan, which can negate some of the negative effects of the colder than normal winter on this pest.

Black cutworm and armyworm moths are among the “early arriver” pests that we see each spring. Reduced winter annual weed growth can be an important factor in reducing the risk of seeing black cutworm damage in fields. Armyworm moths are more likely to lay eggs in grass areas. Wheat fields and areas where we have grass cover crop species that remain green for extended periods are the most likely candidates for egglaying and subsequent damage.

Both species are deposited into the area each spring by thunderstorm events as the pests are carried north from their overwintering areas into our region. Watch for strong pushes of warm and humid southerly air masses for the deposition of these pests.

Enhanced moth migration in areas to our south are an early indicator that trouble may be on the way. Monitoring is the only tried and true method to detect the pests on time as the pest sporadically appear in pockets across Michigan in most years. In corn, some of the Bt events have potential to control black cutworm and armyworm larvae, but not all traits will. Michigan State University Extension Field crops entomologist Christina DiFonzo has updated her excellent trait table for Bt corn for 2015. Refer to this table for more information on which Bt traits control these pests in corn. In corn and wheat, many foliar insecticides can be very effective at controlling pests in the event a rare outbreak does occur in your fields, but finding an outbreak remains the key in avoiding yield losses in these instances.

Soil insecticide and herbicide interactions

As the fear of Bt-resistant western corn rootworm is rising in Michigan, some growers are returning to using soil insecticides to control this pest in continuous corn. It is important to investigate the potential for damaging interactions between some of the newer herbicides and soil insecticides. Crop injury can occur when organophosphate insecticides are used in combination with ALS or HPPD inhibitor herbicides. These crop chemicals are all metabolized by the same enzyme system in the plant. If you are planning on using a soil insecticide, it is important to carefully look at the label for herbicide programs you plan to use to see if a crop damaging interaction is likely to occur. 

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