Soybean Aphid Update as of 6/30/09

The every other year appearance of soybean aphid levels that reach thresholds levels of 250 aphid aphid per plant would be expected in 2009 if history is a guide. The reality is that since 2005 when a high percentage of soybean acres were sprayed we have not seen much of this insect. 2007 was a complete bust due to a April freeze. The question of how bad a year this year will be is still open.

Some area of Ohio and the midwest have found high levels of soybean aphid already on some of the first planted fields. Trumbull and Wayne County (NE Ohio) plus Sandusky have reports of finding low levels of soybean aphid.

I scouted three of the early fields today in Fulton County (these fields were emerged in the Ve stage on 5/16/09) which were V5-R1 stage. I was unable to find any aphid activity on any of the plants. Keep in mind the look alike insect that can be confused with soybean aphid. One field did have an active population of potato leafhopper. The difference between leafhopper and aphid is easily seen with the activity of the insect. Aphid will not move at all while the leafhopper will skate quickly across the leaf when disturbed.

I will continue to scout and let you if we see any development of soybean aphid.

An excellent article highlighting the status of soybean aphid can be found in the 2009-20 issue of the C.O.R.N. newsletter.

Soybean Rust Appears Ready to Repeat History in 2009

Soybean Rust has been a threat lurking in the background of our soybean production seasons since it discovery in the US in November of 2004. SBR's overwintering location in the southern US and the biology of the disease have not come together to threaten the main soybean production areas of the midwest during the growing season. The 2009 season appears to be following the pattern of past growing season-soybean rust is in the south in isolated areas and development is slow enough that we are not concerned in Northwest Ohio. Shown are observation map from June 25, 2008 and 2009. The 2009 map shows more counties with observations of soybean rust as compared to 2008 but the progression has slowed as the weather has dried. This is good news in that the threat of soybean rust is not any greater than historically for 2009.

For more information on SBR see the Ohio State University Soybean Rust website or the SBR PIPE website for US observation information.

Rainfall varies across area

Rainfall varied across Northwestern Ohio from around an inch to over 4 inches from Friday and Saturday night rains based on local reports. The table below shows weather site data available on 6/22. To date we have accumulated 945 GDD since April 1.

Location	Rainfall 6/19-6/20	GDD since 4/1/09
Wauseon	2.31	-
Napoleon	-	-
Montpieler	1.96	-
Toledo Express	2.75	-
Northwest Ag Research Station	2.16	945

Size Matters with Yield Loss from Weeds

Yield losses from competing weeds is a matter of timing and size. Weeds that emerge with the crop are most competitive because the weeds tend to grow faster than the crop they are planted in. This is very true for Giant Ragweed. Picture 1 shows a 8 inch weed in a soybean field. Picture 2 shows a 15 inch weed in the same soybean field. The 8 inch weed has already reduced yield by 5-6% and the 15 inch has reduced yield by 10% plus even when they are removed at this stage based on research from across the midwest. Put a priority on weed control in these fields over the next few days.

Wheat Head Scab-Early Reports Indicate Low Year

Early report from southern Ohio found low levels of head scab in wheat. (See Crop Observation and Recommendation Network Newsletter 2009-18). Early scouting from Northwest Ohio are showing the same. Report from Putnam and VanWert indicate levels less than 3%. Scouting two Fulton County fields yield a 0% rating. One field had a few scattered heads that did not show up in random survey stops and the second field was a true zero with not any scabby heads seen. I will be scouting a few more fields next week.

As far as any other diseases the first field was very clean. The second field did show have some rust and also a physiological burn on the flag leaf. The lower canopy of the field also had stagnospora lesion but this never progressed to the flag leaf.

Replanting Soybeans

Soybean emergence has less than desirable in some areas of fields. Wetter areas or soils with higher clay content and cool conditions have been responsible for thin stands. Much of the replanting going on at this point is the no-brainer type of decision,if there are no plants there is no yield potential. Areas that have stands become somewhat questionable as to whether we patch in or take what we have.

Generally if we have 75,000 plants per acre we can expect near maximum yields. For a 30 inch row we need 5 plants per foot of row, 15 inch rows we need 3 plants per foot, 10 inch rows need 2 plants per foot and 7 inch rows 1 plant per foot to meet this threshold plant number. These type of stands will not suffer yield losses, but weed control maybe more of a challenge which will be a problem for most fields this year given the calendar date and sizes of plants.

Stand of less than 50,000 start to loss 5-7 bushels per acre. While this loss is real it is also a given teat soybeans planted in mid June to early July will not have as great a yield potential as earlier planting dates. So likely the decision to replant even stands at 50,000 is a wash economically.

A couple of good references on the soybean replant decision can be found from Iowa State University and Purdue University for further reading.

How fast does corn grow?

With corn sidedressing just beginning and several days of wet weather for the week some may become concerned about getting the job done before the corn is too tall. In survey's late last week most of the corn was just emerging to V2-3. If we use the leaf collar method of describing corn growth we would like to be done before we hit the V6-7 stage.

Dr Nielsen from Purdue University has a guide for how many growing degree days it takes to advance the crop on collar stage. It takes approximately 82 GDD to grow a leaf collar. For the week of May 25 to 31 we averaged 15 GDD per day. In this case we will advance a growth stage every 5.5 days.

The other fact working for a longer sidedress period in 2009 will be that generally later planted crops do not have as much height to them. So a v6 in 2009 will be shorter than the same stage in an earlier planted year like 2008. We should expect a longer access period to get nitrogen on crops this year.

Do higher corn prices justify more nitrogen?

With rising grain prices and rain keeping us out of the fields it may be worthwhile to take a look at nitrogen rates for 2009. The table shows various nitrogen cost and $4.50 per bushel corn to calculate the maximum return to nitrogen application. Rates that approach 180 seem to be in the ballpark except with nitrogen above 50 cents per unit.

The nitrogen rate calculator for Ohio can be found at: http://agcrops.osu.edu/fertility/documents/New_Nitrogen_Recommendations_2009_new.xls

Crop Progress as of 5/29

I took the usual route along County Road L and County Road B on Friday in Fulton County. As suspected, since 5/19 a lot of progress in planting was made. Corn was planted in 39 fields and were 100% emerged, 38 soybean fields with 50% emerged and 10 fields were not planted. Generally emergence in these fields is excellent. Even a couple of fields with crusted soils on 5/19 have good stands. Corn planting is nearly complete and soybean planting is 98% completed for the county.

There are 10 wheat fields and the growth stage was generally in growth stage 10.5 (flowering) with 1 field at 10.1 (just prior to flowering). While head scab would seem to be a concern, the head scab model shows a low potential for head scab http://www.wheatscab.psu.edu/riskTool_2009.html.