Southwest Michigan field crop regional report – June 6, 2014

Recent rainfall has helped relieve slightly drier than optimal conditions on the sandier soils in Southern Michigan.

Weather

Winds have kept folks looking for herbicide application windows. Some areas of commercial corn are greener than they should be. Rainfall totals average 1.1 inches across the South Central Michigan State University Enviro-weather stations, with a high of 1.8 inches of precipitation since May 25 at the Constantine Enviro-weather station and a low of 0.3 inches at the Ceresco Enviro-weather station in Southern Calhoun County

Rainfall was about the same further to the West, with Dowagiac, Michigan receiving over 2 inches, Lawton, Michigan receiving 1.8 inches and Fennville, South Haven and Grand Junction, Michigan receiving the least, averaging around 0.25 inches. Growing degree day (GDD) accumulation is vastly different before and after the passage of the cold front.

Temperatures struggled to get into the 60s a couple of days since the rain. GDD base 50 accumulation since May 1 average 437 in South Central Michigan and 431 GDD further to the West. We are in the part of the growing season when Mother Nature usually rapidly begins to turn up the heat, with long-term average GDD accumulation of 17.2 and 17.4 GDDs typical of the next one- to five- and six- to 10-day periods. The 6-10 and 8-14 day outlook from NOAA suggests that we should see near normal temperatures and precipitation for the first period, with temperature slipping to below normal with normal precipitation over the latter period.

Crop reports

Commercial corn continues to look good. Rapid growth with the warm temperatures last weekend really spurred on growth and development. We are in the early window for sidedress nitrogen applications for the earlier planted corn. Early applied preemergent weed control programs look good so far. Few problems with insects reported. Delayed preemergence programs and early post-program switching is the norm now, with the planting window spread out and rapid crop and weed growth due to the warmer temperatures. We have had some questions on corn leaf staging. Bob Nielsen, Purdue University corn agronomist, has an excellent resource on determining corn growth stages.

I would not be surprised to see some herbicide damage due to the rapid cool-down following the rains. Warm temperatures should bring plants out of this in short order.

Seed corn planting continued. Wet conditions continued to mess with planting delays of the male rows. Central St. Joseph County and Southern Kalamazoo County had the longest period of the last round of thunderstorms. Most fields look very good. Pounding rainfall in the Schoolcraft, Michigan area might lead to some issues down the road.

Early planted soybeans are growing rapidly and are beginning to look good. Lots of fields have yet to be sprayed, so weed height and competition may be the larger challenge in advanced fields. Good soil moisture levels should help to reduce stress until herbicides are applied. When using glyphosate in Roundup Ready soybeans, be sure to add spray grade ammonium sulfate to the tank before the glyphosate. Also, consider the weed species and size when determining application rate. Another important thing to consider is that we have more volunteer corn in many fields this year due to the heavy thunderstorm that lodged later harvested corn last year. Consider making an application of post-emergence grass herbicide to help clean up these fields this season. It now only will reduce competition and grain quality issues from the volunteer corn, but can also help reduce the chance that western corn rootworms will be a challenge in your fields the following year.

Wheat has been advancing rapidly across the region. Many fields look very good right now. Some fields are beyond flowering. I caught five armyworm moths in a pheromone trap here this last week. While this number is small, growers should still scout fields here to look for typical armyworm feeding symptoms, which are ragged leaf margins. Protection of the flag leaf from insects and diseases is critical in allowing the plants to produce carbohydrates to go into the seed formation. There is limited leaf disease issues in the fields I have walked, however many of them were treated with fungicides earlier.

Alfalfa harvest of first cutting advanced quickly last week. Re-growth has occurred very quickly and looks good. Continue to scout for alfalfa weevil larvae in the re-growth. We also should begin to think about potato leafhopper scouting, especially the re-growth when it is small. This typically is a post-second cutting issue here, but can sneak in occasionally following the first cutting, especially on later harvested fields.

What’s next in pests?

Early sidedress time is when growers begin to notice issues with stands in corn fields. For the most part, this is because we are so busy during planting and spraying that we do not take the time to look fields over that well. A couple of challenges often become noticeable at this time. Growers might see areas or expanses of plants that are losing uniformity of plant height or have missing plants. The following discusses two potential causes for this.

If plants are missing and the damage goes down the row and stops abruptly, check for circular holes around the base of where the plant should be. This symptom is very typical of sand hill crane damage. Once an endangered species, this very common bird has been causing more and more damage to corn stands by pulling up V1-V3 plants and eating the seed attached to the root mass. They can remove an appalling amount of plants because they are large birds. Once the plants have grown beyond the size they can be easily extracted from the soil, damage stops.

When stands are even at planting and rapidly become uneven after V2-V3, and exhibit irregular to almost circular pockets of significant to complete stand loss, and you do not see the round holes in the soil, the culprit may be white grubs. The most aggressive species feeding on corn roots is the Asiatic garden beetle grub. It can be identified from other white grub species by the presence of white bulbous pulps in the cheeks. Damage from this invasive species was first noted in Michigan in St. Joseph County in 2007. Adults have been noted in most counties in Southern Michigan over the last several years.

Damage from these pests is extremely sporadic. One field may have severe damage, while all surrounding fields may have almost none. Damage often occurs on sandy hilltops of fields where the previous crop was soybeans, alfalfa or potatoes. There are no effective rescue treatments. Soil insecticides or “1250” level seed treatments can help in subsequent years if the problem re-occurs. Even these treatments may not be effective if the number of grubs is very high. Winter annual weeds are thought to provide root tissue to help the larvae to “bridge” until the crop roots are available for feeding.

Other Michigan State University Extension field crop regional reports from this week:

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