Southwest Michigan field crop regional report – July 10, 2014
Update after last week’s severe storms.
Strong storms of a week ago left many corn fields with corn plants facing every direction but up. The good news seems to be that there were limited amounts of green-snap in commercial corn fields, somewhere in the 3-8 percent range in most fields. Damage may have been somewhat higher in seed corn production fields, especially in portions of St. Joe and Branch Counties. Root lodging was severe in many fields, but a lot of these fields have recovered quite nicely as the plants have goose-necked, but the hope is that the yield potential will return to near normal. Conditions continue to be very wet, with thunderstorms contributing the majority of the rainfall.
NOAA’s 6-10 day and 8-14 day outlooks are in pretty close agreement. They both predict below normal temperatures and above normal precipitation levels. Rainfall totals have been generous in Southwest Michigan, with rainfall at Three Rivers at 16.47 inches since April 1, over 6 inches above the normal precipitation for the growing season. Most of this rain has occurred in the last month. Growing degree days (GDD) as of July 6; the Three Rivers area was at 1040 GDD’s base 50 since May 1. This is about 40 GDD’s behind the 2013 growing season and 65 ahead of the long term average for southwest Michigan. The heat is usually on in southwest Michigan in early July, with 20.2 GDD’s per day typically accumulated through July 11, and 20.4 GDD’s per day through July 16.
Advanced corn fields are approaching tasseling rapidly. Later-planted corn is approaching V7-V8. Nitrogen continues to look to be a challenge based on coloration. Heavy rainfall may have led to leaching and de-nitrification losses in some fields here. Some nitrogen has been applied by air to help growers get into wet fields. Irrigation has been applied to some fields that needed an additional shot of nitrogen to keep the crop green. Corn is speeding towards pollination. Weed control for pre-emergence programs looks good. Some post emergence sprays have been hit-or-miss due to tall weeds at the time of application. Growers here have had to choose their battles when application windows have arisen.
Seed corn fields have many of the same issues that commercial corn fields have. Lodging may present some challenges with de-tasseling operations, particularly on the side where the wind was blowing towards. A return to sunny, lower humidity conditions which are anticipated over the next 3 days should help to allow access into fields by the end of the period. Fungicide applications at Vt may be in order if we return to wet conditions following the weekend and the forecast holds true. Some fields have reasonably high populations of first generation European corn borers.
The most advanced soybean fields are at R2. Many later-planted fields are approaching R1. Early beans look good. Later-planted fields have spotty weed control issues, similar to corn. Rainfall has allowed the crop to grow rapidly. Bean height and long internode spacing will likely be challenges this summer. We have almost the perfect setup for white mold with full canopy closure. We normally look for white mold after soils are saturated for 24 to 48 hours, which creates opportunities for the sclerotia to germinate. Any wounds, including sepal separation wounds from the flowers at petal fall, can create an opportunity for spores to germinate and cause infection of plants. Martin Chilvers, MSU field crops pathologist, emphasized that R1 is the growth stage where fungicide applications are most likely to have a chance to reduce the incidence and severity of white mold. Chilvers and Mike Staton, MSUE soybean educator, highlighted considerations for spray boom height and materials in their 2012 article, Applying Foliar Fungicides for Control of White Mold in Soybeans.
Chris DiFonzo, MSU field crops entomologist, reports that there are very few soybean aphids being found in the Midwest this summer. Japanese beetles are emerging, and may be feeding on soybean leaves soon. It takes incredible amounts of defoliation to impact soybean yields, so it is unlikely that these pests will ever reach levels that approach thresholds for control. Early onset Sudden Death Syndrome (SDS) is evident in more fields this year. It looks as though SDS continues to spread throughout the region, although the majority of symptoms will still be occurring in mid to late August.
Wheat harvest has begun in fields that were planted early. The majority of fields in the region should be harvestable in about 7 days. Wind-driven rains lodged some fields, but the majority look decent at this point. Most treated fields have low incidence of head scab. Powdery mildew was the most common leaf disease. It crept up on some untreated fields to the flag leaf on susceptible varieties.
Winds damaged vines in many cucurbit crops early last week. Growers are reporting fungal pathogens on the rise in a wide variety of crops. Growers should be on watch for downy mildew in all cucurbits. Contact us if you are seeing downy in your fields. Mary Hausbeck recently published an article that is excellent on methods for controlling downy in your fields. Extension Educator Ron Goldy at MSU’s Southwest station reminds growers not to forget copper applications to help reduce the risk of bacterial infection, especially on wind-damaged vines.
In potatoes, MSUE Potato Pathologist Willie Kirk reports that late blight was found in fields in Howe, Indiana. in a July 6 article. The lab is checking into Ridomil resistance for the strain found near Howe. With cooler and wetter than normal conditions in the forecast, the stage is set for a prolonged infection period.
Tomatoes and peppers have increased risk of bacterial diseases due to the winds of last week. Early blight and now late blight are also potential diseases to protect against.
Snap beans are particularly susceptible to root damage and rots due to heavy rainfall. Potato leafhopper numbers are on a rapid rise, so fields should be checked regularly. European corn borer numbers are elevated in pockets of St. Joseph County.
For more specific vegetable pesticide recommendations, go to the MSUE 312 Crop Specific Recommendation Page.
Alfalfa growers continue to struggle with finding windows of opportunity to harvest. Most successfully harvested fields have minimal time on the ground this season. Operations such as tedding have had an impact in allowing hay to dry more quickly. Growers should be on the lookout for increased numbers of potato leafhoppers in fields across the southwest region. Many fields in the southern most areas of St. Joe county have seen hopper burn in untreated fields.
Thresholds (Varies with plant height in inches):
- Under 3 inches = 20 adult PLH/ 100 sweeps
- 3 to 8 inches = 50 adult PLH/ 100 sweeps
- 8 to 12 inches = 100 adults and/or nymphs/ 100 sweeps
- Over 12 inches = 200 adults and/or nymphs/ 100 sweeps
Other Michigan State University Extension field crops regional reports from this week: