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Issue
1 - May 2, 2007 Sign up for the SWROC Crop Production list serve IPM Stuff Classics Corn
Planting Depth - 3/5/99 SWROC Pages: Home Page Other Cropping Newsletters: Minnesota Crop eNews - Regional Newsletters Minnesota Fruit and Vegetable IPM News The Bulletin - Other States IPM Newsletters
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To keep up to date on all the crop weather details during the growing season see: http://swroc.cfans.umn.edu/Weather/weather.htm.
More wind. Corn was somewhat beat up last week. Yield effects will be minimal unless this blasted wind doesn't stop. Heavy rainfall and localized areas of hail occurred over portions of SW MN the night of 6/10-11. Unfortunately, mortality of crops standing in water happens more quickly under warm conditions.
Yield penalties for re-planting corn at this date are 30-35 %. The corn growers field guide for evaluating hail and replant decisions by Dale Hicks will help with decisions the unfortunate case of hail. A printable version is available at http://www.soybeans.umn.edu/pdfs/CornGuide.pdf.
Herbicide application is not
the only issue with this spring's weather; fly casting in the wind is
a challenge. Nightlife
at Lamberton and Fulda Nocturnal insect flights are most impressive on warm, calm, humid nights. A large and ever-changing number of species will be flying from now until early fall.
Unusually heavy Forage looper flights continue in the area. I have not tried to identify any of these moths. The Clover looper is related and of similar appearance and some of the moths currently flying may be the latter species. The Fulda trap caught over 200 of the moths over the weekend. A macabre Jonestown like scene appeared in one of many Lamberton pan traps placed to analyze soybean aphid landing rates. It is easy to understand why moths would reach an untimely end by attraction to light traps. Why would they land en masse mass into a container of anti-freeze? Were they caught in a freak wind downburst, was there an irresistible lunar reflection, or were they all following a misguided leader? Just another one of many SW MN entomological mysteries, of no economic importance, that will remain unanswered.
Alfalfa - Potato leafhoppers (PLH) populations are a concern. Watch for economic populations in this second cutting. I haven't been in any alfalfa lately but did see "hopper burn" on late planted soybean seedlings. The photo to the right shows the wedge shaped injury on the unifoliate leaves. Yield impact of such injury is unlikely unless pressure remains high and growth is delayed. PLH is a suspect in the occasional cases where neonicitinoid seed treatments have resulted in soybean growth differences at Lamberton. These growth differences do not always result in increased yield.
This is starting to shape up as a good year for PLH in SW MN.
Cereal grains - Wheat and oats are heading now in Southern MN and the management period for this crop is coming to an end. Small grain aphids are present but not at panic levels. See http://nwroc.umn.edu/ent/redent.html for more information on cereal aphid management.
Corn
- Corn growth continues to be amazingly rapid. Yellow corn is rare and
can usually be attributed to one of several causes: 1)Excessive moisture
moving or denitrifying N, 2) Nutrient (N,S) immobilization on residue,
3) Soil type and application related nutrient deficiencies (N, S, Zn),
3) Heavy weed pressure competing for N and 4) Poor root systems caused
by planting depth or disease issues limiting nutrient and moisture uptake.
Fortunately, yellowing caused by glyphosate applications to non-glyphosate
tolerant corn is relatively rare. The differential growing environment
with in-row residue can be seen in uneven corn height.
Yellow beans have returned.
Sure, an inappropriate variety could have been planted into iron deficiency
chlorosis (IDC) prone soils and is always the first item to check.. Root
rots may be an issue and can usually be found under chlorotic soybeans.
Soybean cyst nematode (SCN) should also be suspected. Don't be misled
into assuming that SCN cannot be the problem where an SCN resistant variety
was planted. Three things could go wrong: 1) Very high SCN population
densities can overwhelm resistant varieties through juvenile feeding causing
root damage and allowing pathogen entry. 2) The variety may not have received
the full compliment of resistance genes, allowing more nematode reproduction
than more fully resistant varieties. 3) The genetics of SCN in the field
may not be controlled by the resistance source in the variety planted.
The latter case is the most serious issue for long term SCN management.
Examine root systems for nematodes on resistant varieties several times
during the summer to ensure things are going according to plan.
Seed corn maggot adults are quite numerous. Injury to the cotyledons and growing point of emerging soybeans was observed at the Southwest Research and Outreach Center was observed the past week. The soybeans were planted into a very weedy field that had been tilled the day before.
Bean leaf beetles (BLB). Overwintering populations are gradually declining. I'll calculate an approximate date for 1st generation BLB emergence for next issue.
Soybean aphid (SBA) - It's still too early to worry in any of the SW or any MN fields that I am aware of. However, this is an interesting year. Reports of aphids to the east continue. U More Park at Rosemount continues to have the most intensively counted aphids anywhere in the state. Van Larson reported aphids near Rochester. Based on the lack of enthusiasm in his e-mail, he is not an aphid researcher. I suspect that most agriculturalists could do with an aphid free summer. Closer to home, the typical Minnesota River Valley fields in Brown and Nicollet County have aphids. They are easy to find in some of the early planted fields. We had aphids in early planted soybeans at Lamberton before June 6th. From Yellow Medicine County, Dorian Gatchell is seeing some aphids in the fields that are typically infested first in Yellow Medicine County. I was trying to help sort out an SCN, root rot, iron deficiency chlorosis puzzle in a Watonwan county field. Aphids were present at low numbers on the still green edge of this early planted field. Based on the size/age of infested soybeans, the migration from buckthorn to soybean happened quite early. NW MN appears soybean aphid free at this point but can still receive migrants.
The distribution of aphids in the southern part of the state is quite wide considering the early calendar date.
Remember that each field is unique. Although early season populations are concerning and this insect bears close watching again in 2007; many factors can still slow down or stop a 2007 SBA outbreak.
Prophylactic insecticide applications
for soybean aphids are very, very risky business. just a gentle reminder.
SCN resistant soybeans - When to say uncle 2007 Soybean aphid forecast - They don't get the weather right either Crop production events in SW MN Thursday, July 12 - SWROC Summer Field Day Friday, July 13 - WCROC Summer Station Days Thursday, September 6 - This one's not in SW MN but should be good. Regional Soybean cyst nematode resistance management summit Best Western North Mankato, MN
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European
corn borer (ECB) flights continue to be very low at the Lamberton
and Fulda locations. A few locations are a bit higher and can be seen
at 