Weekly Field Crop IPM Report

By Ned Birkey, MSU Extension Educator Emeritus; Spartan Ag; April 21, 2022

?Weather????????The minimum soil temperature at the 2-inch level at the Deerfield MSU Enviroweather station has struggled recently, at 36.8 oF on Wednesday, April 20, 39.2oF on April 19 and 40.4oF on Monday, April 18.?A weak to moderate La Niňa of the cooler water temperatures in the equatorial Pacific Ocean means the longer this cooling persists, the greater the chance of a dry summer here and a more active hurricane season in the Atlantic Ocean and Gulf of Mexico.?Despite a stretch of drier weather coming, Eric Snodgrass of Nutrien is forecasting cooler than normal temperatures for the next 10-15 days after a nice weekend warming teaser.?

?Forage Stands??????????Winter injury of forage stands may be serious due to extensive wet soils and root rots.?Short season forage options include oats, triticale, barley or Italian ryegrass planted as soon as possible now.?For later spring plantings, sudangrass, sorghum-sudan or pearl millet are options.?For thin stand planted last year, farmers should try interseeding to thicken up the thin spots.?Autotoxicity in alfalfa is not a problem until stands are more than one year old.?Otherwise it might be better to wait until late summer to interseed damaged stands.?

?Corn??MSU’s Chris DiFonzo issued her first insect report about Black cutworm moths arriving in Michigan.?She is also trapping for true armyworm.?The good news about the cooler weather is that it will slow down insect development as insects are cold blooded and their development can be largely predicted by growing degree days (heat units).?Despite the forecast for cooler than normal temperatures returning next week, and even another chance of frost, drying soil conditions will allow planters to start rolling.?Farmers should remember that planting date is only one of the factors affecting yield and pick their earliest fields to plant carefully.

?Soybeans ??????Bean leaf beetles (BLB) overwinter in soil and plant debris and will emerge and migrate to available host plants such as alfalfa, trefoil and clovers.?We have been over threshold of BLB in mid-April of very early planted soybeans, a preferred host plant, though this has been rare.?Our fluctuating spring air temperatures, along with a lack of snow cover, can negatively influence the population, likely resulting in more mortality this past winter.?Fields with a history of bean pod mottle virus, or soybeans planted near alfalfa fields, should be scouted first.

?Terminating Cover Crops this spring may be limited to herbicides if wet soils limit tillage as an option.?Products like paraquat (Gramoxone; group 22), glufosinate (Liberty; group 10), or glyphosate (Roundup; group 9) are the best options.?Glyphosate is the most consistent option, especially as cover crops increase in size.?Group 1 herbicides such as clethodim and fluazifop do not provide effective consistent control of cereal rye.?If cereal rye or other grass species were seeded with a legume, farmers may need o add 1,4-D or dicamba with glyphosate to improve control.?This can also be helpful if broadleaf winter annual are present.?Remember that cool soil temperatures can slow growth and herbicides are most effective on actively growing weeds.?Ideally terminate cover crops 10 to 14 days prior to planting corn.?Options other than herbicides include rollers, stalk choppers and crimpers to flatten stems??????

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