C.O.R.N. Newsletter 2013-26

Dates Covered: 
August 13, 2013 - August 20, 2013
Editor: 
Rory Lewandowski
Soybean Aphid Update

Soybean Aphid Update

We are receiving our first reports of soybean aphids reaching levels that require insecticide treatment in counties just south of Lake Erie.  Mid-August is time of the summer when we normally see outbreaks in Ohio.  Because of this, we would urge growers to check their soybean fields to see if aphids are reaching threshold levels.  However, because the majority of reports indicate low population levels, we recommend that growers only treat fields that have been scouted and where thresholds of 250 aphids per plant are reached.  See the fact sheet at http://ohioline.osu.edu/ent-fact/pdf/0037.pdf for further information.

Stink Bugs on Soybeans

Stink Bugs on Soybeans

As we get into the full pod and beginning seed development stages, we need to turn our attention to possible problems with stink bugs, mainly the green stink bug and red-shouldered stink bug.  But before we limit ourselves to those two, keep in mind that we are still anticipating the brown marmorated stink bug becoming a problem on soybeans.  Because stink bugs cause direct injury to the pods and seeds, it takes fewer of them to cause economic losses.  Losing an average of only 1-2 seeds per plant will equal the cost of an insect application.  Thus, growers across Ohio should scout their fields for stink bugs with either a sweep net or by hand.  When sweeping, the threshold for regular soybeans is four or more stink bugs, adults or nymphs, per 10 sweeps.  For soybeans grown for seed or food grade, we would lower the threshold to two per 10 sweeps.  If counting the stink bugs directly, two stink bugs per foot of row throughout the field is the threshold, with just a single stink bug as the threshold for seed and food grade soybean.  However, these levels should be across the field and not only in a few locations.  More information on stink bugs can be found on our newest fact sheet available at http://oardc.osu.edu/ag/images/StB_Factsheet_June_26.pdf

Assessing the 2013 Corn Crop : The Ohio's Country Journal Crop Tour, August 7-8, 2013

Last week I had an opportunity to participate in The Ohio Country Journal Crop Tour (http://ocj.com/2013/08/2013-i-75i-71-ohio-crop-tour-summary/) which evaluated the status and condition of the corn and soybean crop in 40 counties across the state. I was part of a team that visited 20 fields in the western part of Ohio – the I-75 tour. Another team evaluated corn and soybean crops along I-71. We stopped at fields that allowed an assessment of a corn and soybean field in close proximity. Yield checks were based on the “Yield Component Method” described in last week’s C.O.R.N. newsletter (http://corn.osu.edu/newsletters/2013/c.o.r.n.-newsletter-2013-25/estimat...). However, time constraints (about 20 minutes per field) limited our yield assessments  to no more than three sites within each field.

The following are some preliminary observations made by the I-75 team for corn.

Yield estimates for the 20 fields ranged from 160 to over 300 bu/A. (The yield range for the I-71 tour was 135-200 bu/A). More details concerning yield estimates are available at http://ocj.com/2013/08/2013-i-75i-71-ohio-crop-tour-summary/. Keep in mind that the Yield Component Method for estimating corn grain yield is probably only accurate within plus or minus 30 bushels of the actual yield.

In most fields, the corn crop had been established using conventional tillage following soybeans.

Plant populations averaged 28,800 plants/A and ranged from about 23,000 to 40,000 plants/A.

Of the 20 fields evaluated, we encountered one field planted in 15-inch rows and one planted in 36-inch rows. The remaining fields were planted in 30-inch row spacings.

Most of the corn was at the early dough stage. Some fields were at the late blister stage and are still  vulnerable to kernel abortion which may occur until the dough stage.

Despite above average rainfall at most sites, foliar disease  development was generally limited - primarily gray leaf spot  and northern corn leaf blight confined to leaves well below the ear.

Very little insect feeding was present. Weed pressure was high in only one of 20 fields.

Despite the potential for N losses due to persistent  rainfall, which saturated soils periodically, there was little evidence of N deficiency – “leaf firing”. If present, it was limited to the lowest leaves.

There was evidence of wind injury , root lodging and green snap, in 8 of the 20 fields. Green snap damage (associated with loss of stand) appeared significant in only two fields. It also did not appear that the root lodging present would impact harvesting.

Wheat Performance Results for 15-Inch Row Spacing Available Online

Performance results for wheat grown in 15-inch row spacing are available online at: http://oardc.osu.edu/wheattrials/Ohio_Wide_Row_Wheat_Summary_2013.pdf.   

The varieties selected for evaluation in 2013 were in the top half of the 2012 Ohio Wheat Performance Test.  In 2013, the varieties averaged 82.9 bushels/acre with a range of 75 to 89 bushels/acre across both locations.  Table 1 gives results for the Crawford and Wayne County locations.  Table 2 gives two-year summary results. For each variety, yield at 13.5% moisture, test weight, percent moisture, spring stand, lodging, height, and heading date are given.  Heading date was the average calendar day of the year on which 50% of the heads were completely emerged (i.e., Day 136 = May 15).   Seeding rate was 25 seeds per foot of row for all varieties.  It should be noted that this is a stand-alone test and comparisons should not be made with the results published at 7.5-inch row spacing in the Ohio Wheat Performance Test. 

Variety selection is very important when growing wheat in 15-inch row spacing as yield is influenced by wheat variety.  This year we had a trial at two locations to examine the effect of four wheat varieties and two row spacings on wheat yield.  On average, yield decreased by 2.5 and 5 bu/ac at Wood Co. and Wayne Co., respectively, when grown in 15-inch row spacing compared to 7.5-inch row spacing.  Wheat performance results of wheat grown in 15-inch row spacing provides information for growers who are interested in growing soft winter wheat in 15-inch row spacing to utilize precision planting implements or Modify Relay Intercrop (MRI) soybeans with wheat.  In a MRI system, soybeans are planted between wheat rows when wheat is headed (Feekes 10 growth stage).

Weather Update and Outlook

After some scattered early week rain into early Tuesday across the state, the rest of the week of August 12 will feature below normal temperatures and below normal rainfall. Little rainfall is expected from Tuesday through early weekend across the state. Highs will mostly be in the upper 60s north and 70s elsewhere with lows in the 50s. Some mid to upper 40s in low lying areas are possible later in the week especially Thursday.

The week of August 19 will see a return to slightly above normal temperatures (especially on low temperatures) and rainfall near normal (slightly below west and north and slightly above southeast).

Through August 25, overall, temperatures will average near to slightly below normal and rainfall will average near to slightly below normal. Normal rainfall for the 2 weeks is about 1.5 inches for this time of the year. Again, remember, August rains are variable due to the convective nature (thunderstorms) of the rainfall. Our outlooks are based on averages over the state as we can not forecast rainfall on a small-scale during the summer for the most part.

Normal highs are 80-85 and normal lows are 60-65.

The latest 2 week rainfall outlook can be found at the NWS Ohio River Forecast Center website: http://www.erh.noaa.gov/ohrfc/HAS/images/NAEFS16day.pdf

 

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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.