May 26, 2005
In this issue
§ Ballad biofungicide registered for soybean rust and can be used for organic soybean production
§ Soybean aphid update
§ Editor’s Note: What is an agricultural experiment station?
§ Speedier scouting of soybean suckers?
§ Watch for weed escapes after soil applied herbicides in corn
§ Control weeds now – don’t delay!
§ Post-emergence herbicide strategies in non-GMO soybeans
§ 2005 MSU Weed Tour
§ MSU Crop Management and Field Diagnostic School - July 27
§ Regional reports
§ Weather news
AgraQuest announced that Ballad biofungicide has received a Section 3 label for the control of soybean rust in soybeans. At present Ballad is the only OMRI approved fungicide to control rust in organic soybean production. Ballad's active ingredient is Bacillus pumilus, which when used as a protectant fungicide controls a wide range of fungal pathogens. Agraquest has data from South Africa to support their efficacy. This data is shown in the accompanying figure.
Last week I reported winged aphids on the buckthorn at my house near East Lansing. This week, those aphids are gone from my plants. All were winged in the last generation, and they flew away to their death in the woods surrounding my house.
However, Mary Gardiner, a graduate student working in the
MSU Biocontrol Lab, found winged aphids on buckthorn on May 25, near the
Bean and Beet research farm in Saginaw County. For those of you familiar with
the area, the back edge of the farm is bordered by a “Rails to Trials” that is
full of buckthorn. Bottom line – winged aphids are moving from buckthorn and
looking for soybean!
You may note that in Chris DiFonzo’s soybean aphid update, she mentions researchers working at the Bean and Beet research farm, a field research station of the Michigan Agricultural Experiment Station (MAES). Each of MAES’ 15 research stations focuses on the agricultural, natural resources and rural community needs of its particular location. They provide important sites for MSU specialists to conduct their research under Michigan’s diverse conditions. Please continue to support the work of the Michigan Agricultural Experiment Station.
The current soybean aphid action threshold is based on number of aphids on whole plants, that is, 250 aphids per plant. But counting aphids can be time consuming, and it takes a good eye to see small individuals. Sure, university-types like myself have ample free time to sit around and gaze at plants. But for crop consultants, Extension educators and growers, an ideal aphid scouting method would be quick and easy so more fields can be covered in a shorter amount of time. That’s where “Speed Scouting” may be helpful.
Speed Scouting was developed by entomologists (Hodgson, McCornack, and Ragsdale) at the University of Minnesota. It classifies plants as either infested or uninfested, and then uses the total number of infested plants to make a decision. For those of you working in wheat, this is similar to the presence-absence scouting method used for determining spray applications for grain aphids. A speed scouting data sheet is included here. You can copy this sheet, or access the original from the University of Minnesota soybean aphid web site at: www.soybeans.umn.edu. This site also gives answers to Frequently Asked Questions about Speed Scouting.
Let me say up front that Speed Scouting is fairly new, and is not as well researched as the 250-per-plant action threshold currently recommended by Extension entomologists. Speed Scouting has not been validated in a year with widespread, heavy aphid pressure. In 2005, researchers across the Midwest will cooperate with the University of Minnesota to validate the method and compare it to the 250 threshold. Until Speed Scouting has more research behind it, using a threshold of 250 aphids per plant is the preferred, better-tested method. However, I recognize that during an aphid outbreak, there may not be the time or expertise to scout each field; Speed Scouting is at least better than no scouting. And compared to spraying on a calendar date as insurance, at least Speed Scouting will provide some guidance in making a decision, even if it needs further tweaking.
For the purposes of Speed Scouting, a plant with 40 or more aphids is considered to be “INFESTED.” A plant with low aphid numbers, (39 or fewer) is considered to be “UNINFESTED.” What if the plant has more than 40 aphids? STOP COUNTING! You have enough information to classify the plant as infested! In the words of Erin Hodgson, who developed this method, “This is what makes speed scouting speedy.”
Keeping in mind the definition of infested and uninfested – enter a field and pick a plant at random. Count the number of aphids on that plant (count only up to 40!) and classify that plant as infested or uninfested. Mark your result on the data sheet. I suggest using a minus sign [-] for uninfested plants and a plus sign [+] for infested plants. Choose a direction, walk 30 paces or rows, and sample another plant. Repeat the first step ten more times, to sample 11 plants, with 30 paces between each plant (fill in the first 11 spaces on the data sheet). Record the total number of infested plants in the first box and use the table on the right side of the sheet to make a decision.
§ If 6 or fewer of the 11 plants are infested, the aphid population in the field is low. You can STOP SAMPLING, because your decision is Do Not Treat. But return in seven to ten days to recheck the field!
§ If 11 of 11 plants are infested, aphid numbers are high. Your decision is again easy - STOP SAMPLING and spray the field within the next few days!
§ If between 7 to 10 plants are classified as infested, KEEP SAMPLING. You don’t have enough information yet to make a spray decision. Examine five more plants.
When sampling in increments of five plants, add the number of infested plants to the previous total. Use the table on the right side of the data sheet to make a decision. Keep sampling increments of five plants until you can make a decision OR until a total of 31 plants have been sampled. If after sampling 31 plants no decision was reached, STOP SAMPLING and come back in three to four days to resample. These are the most difficult fields, because aphids are present in moderate numbers, but the scout does not know if populations are increasing or decreasing (thus the need to return in several days).
§ Less time spent counting. You never have to count more than 40 aphids per plant. For heavily infested plants, a simple glance is enough to classify it as a “+”.
§ Fields that are heavily infested or that are not infested are classified quickly, after looking at as few as 11 plants.
§ Data sheet is simple. Simply record and count minuses and pluses. No need to calculate the average number of aphids per plant with a calculator or cell phone.
a. You sampled 11 plants and classified 4 plants as infested. What is your decision?
b. You sampled 11 plants and classified 9 plants as infested. What is your decision?
c. You examine 11 plants in a field, counting ALL the aphids on each plant (I don’t know why – you just like counting). Your totals are the following: 15, 66, 35, 68, 40, 128, 34, 92, 49, 55, 33. What is your decision using speed scouting?
d. Given the data in letter ‘c’, what is your decision using the 250 threshold?
e. You sampled 11 plants, but had to continue sampling two more times. The number of infested plants in each group is the following: 7 of 11; 4 of 5; and finally 2 of 5. After sampling a total of 21 plants, what is your decision using speed scouting?
f. Similar to question ‘e’- you sampled 11 plants, but had to continue sampling four more times. The number of infested plants in each group is the following: 10 of 11; 4 of 5; 4 of 5; 4 of 5; and finally 5 of 5. After sampling a total of 31 plants, what is your decision using speed scouting?
g. Why might it have taken you so long in Question ‘f’ to reach a decision?
Many fields did not receive rain for more than two weeks after planting and preemergence herbicides were applied. When preemergence herbicides do not receive rainfall shortly after application, a reduction in weed control often occurs. Therefore, it is especially important this spring to monitor fields closely for weed escapes.
There are several herbicide options for postemergence weed control in corn. The best choice for any given field depends on the specific situation. Three of the critical factors to consider when selecting a postemergence herbicide in corn are:
1) Rotation plans
2) Corn growth stage
3) Weed species/size in the
field.
Table 1 describes crop rotation restrictions, corn growth stage limitations and effectiveness on common weed species for several postemergence herbicides. Herbicides in Table 1a can be used with any corn hybrid. Table 1b includes herbicides that can only be applied to hybrids specifically resistant to the herbicide. For example, glyphosate only with glyphosate resistant (Roundup Ready) hybrids, Liberty only with Liberty resistant (Liberty Link) hybrids, or Lightning only with imidazolinone resistant (Clearfield) corn hybrids.
Detailed information on crop rotation restrictions and effectiveness ratings is available in the 2005 Weed Control Guide for Field Crops (E-434).
Early season weed competition may be one of the biggest contributors to unseen yield losses in corn and soybean. With over 85 percent of the corn and 70 percent of the soybean acres in Michigan planted, one of the next steps growers should be considering is postemergence herbicide applications for weed control. Appropriately timing these applications is critical to preserving crop yields. Several studies have shown that delaying postemergence weed control strategies can substantially reduce crop yield. This has become more of a concern with the large number of Roundup Ready corn and soybean acres that rely on postemergence applications of glyphosate for weed control. We are not saying that postemergence herbicide application timings are not important in non-Roundup Ready corn and soybean; but herbicides generally used in these crops are most effective on small weeds. Therefore, growers that are growing non-Roundup Ready crops are probably already making postemergence herbicide applications early. If they are not it is important to also follow the below outlined guidelines for postemergence herbicide applications.
In Roundup Ready corn and soybeans, there is the temptation to delay postemergence glyphosate applications until all of the weeds have emerged. Delaying these applications can rob corn and soybean of their maximum yield potential. As mentioned before, research throughout the Midwest and Canada has shown the importance of early season weed control. For example, research conducted in Ontario has shown that delaying herbicide applications more than four weeks after soybean emergence can reduce soybean yield ~0.75 bushel/acre/day. In corn herbicide applications delayed more than three weeks after corn emergence reduced corn yield ~0.5 bushel/acre/day.
Over a four-year period MSU conducted research to study the effect of glyphosate application timing and row spacing on corn and soybean yield loss from weed competition. This data is summarized on the enclosed fact sheet Weed Competition in Roundup Ready Soybeans and Corn. This research showed that in at least one of the years that this research was conducted, if weeds were allowed to reach six inches in height before control, yield was reduced narrow row soybean and 30-inch row corn. Depending on when this yield loss occurred, soybean yield was reduced from 0.6 to 1.25 bushel/acre/day and corn yield was reduced between 1.3 and 5.3 bushel/acre/day. This starts to add up when you consider the economics. Considering these crop loss estimates, delaying herbicide applications three days would cost you any where from $7.80 to $31.80/acre in corn ($2.00 new crop corn) and $11.07 to $23.06/acre in soybean ($6.15 new crop soybean). Waiting to make postemergence herbicide applications can cost you money. Therefore, it is important to follow the accompanying recommendations to avoid yield losses due to early season weed competition.
Weeds should be controlled in:
§ 15-inch row corn before weeds exceed 2-inches
§ 30-inch row corn before weeds exceed 4-inches
§ 7.5 and 15-inch row soybean before weeds exceed 4-inches
§ 30-inch row soybean before weeds exceed 6-inches
While good weed control can be achieved in non-GMO soybeans, it is more challenging than in Roundup Ready soybeans. Because of this, we have provided the following list of practices for maximizing weed control and reducing crop injury in non-GMO soybeans.
Scout your fields and select herbicides that provide good to excellent control of the emerged weeds you find. Table 2F in the 2005 MSU Weed Guide for Field Crops contains weed response ratings for all postemergence soybean herbicides.
Use the proper spray additive. This information is listed in the product labels and Table 2I of the 2005 MSU Weed Guide for Field Crops.
Apply the herbicide(s) before the weeds reach four inches tall. Most weeds become more difficult to control as they exceed this height, and you will not be able to increase the herbicide rate for tall weeds as is possible with glyphosate.
Apply the herbicide(s) when the weeds are actively growing. Herbicide absorption is reduced when weeds are drought-stressed resulting in poor weed control.
Reduce the likelihood of crop injury. Postemergence herbicides can injure soybeans whenever herbicide absorption rates exceed the plant’s ability to metabolize the herbicide. Hot, humid conditions increase postemergence herbicide absorption rates. Cold temperatures occurring immediately before postemergence applications can also increase the likelihood of crop injury by reducing herbicide metabolism rates. Table 2F in the 2005 Weed Control Guide for Field Crops contains crop response ratings for all postemergence herbicides. Adjuvants also have a large effect on postemergence herbicide absorption. In general, the order that adjuvants increase absorption from least to greatest is ammonium fertilizer, nonionic surfactant, crop oil concentrate, and methylated seed oil.
Pay special attention to controlling common lambsquarters and giant ragweed. Lambsquarters can be difficult to control with postemergence herbicides in non-GMO soybeans. Harmony GT and Raptor are the only postemergence herbicides that control lambsquarters. Harmony GT will control lamsquarters up to four inches tall. Raptor is effective up to three inches. Harmony GT is among the more injurious herbicides to soybeans. Giant ragweed is difficult to control with postemergence herbicides due potential ALS herbicide resistance, an extended germination period and because it grows so quickly. Check fields containing giant ragweed frequently to determine the optimum application timing.
Control perennial weeds in the previous crop if possible. Perennial weeds are not effectively controlled by most postemergence herbicides.
We invite you to make plans to attend the annual Michigan State University Weed Tour, beginning at the MSU Crops Field Lab on Wednesday, June 29. The MSU Crops Field Lab is located at the corner of Mt. Hope Road and Beaumont Road just south of MSU’s campus. Registration begins at 9:00 AM, with the field tour kicking off at 9:30 AM. The tour will provide ample opportunity to look at research plots and participate in some short field presentations (Be sure to bring a hat and sun screen!). Participants can compare their favorite corn and soybean herbicide programs to other commercial programs, examine how plant population and row spacing affect weed control and evaluate how new transgenic crops (CRW-corn) interact with weed management strategies.
The morning tour ends with lunch. The afternoon tour will begin at 1:00 PM at the MSU Horticulture Farm (College Road, south of Jolly Road) and will include weed control research in horticultural crops. Pre-registration for the tour is $25 per person, which includes a tour booklet and a lunch ticket. You can access a flier with a map and registration form in pdf here. If you have any questions, or would like additional information, please call Deb Misiak at 517-355-0271 ext. 1112.
Want to sharpen your diagnostic skills and stay on top of the latest information in production agriculture? If so, we have the perfect opportunity for you. We would like to invite you to attend the third annual MSU Crop Management and Field Diagnostic School. This event is scheduled for July 27 at the MSU Plant Pathology Research Center on the south side of the MSU campus. This event is open to all who are actively involved in production agriculture (growers, agri-business reps, Extension educators, and agency personnel).
Participants will have the opportunity to hone their field decision-making and problem-solving skills as they interact with MSU Extension Specialists in small groups while participating in hands-on field activities.
The school will focus on such topics as scouting and using appropriate application technologies to manage Asian soybean rust and soybean aphid; fine-tuning fertilizer recommendations; diagnosing herbicide injury and sharpening weed identification skills; and diagnosing and management of nematodes and plant disease problems in field crops.
Approval is pending for RUP credits and 6.0 continuing education units for certified crop advisors (CCA).
The $125 registration fee is due July 15. Participation is limited to the first 125 paid registrations. For more information contact any MSU Extension office or call 517-355-0271, ext. 108 or e-mail lisaingr@msu.edu. A brochure with the registration form is enclosed in this issue and can be found at: http://www.ipm.msu.edu/CAT05_fld/pdf/2005diagnosticschool.pdf
This past week has seen some scattered and warm rain on Sunday (May 22) and Tuesday (May 24). Cloudy conditions have kept temperatures cooler than normal. The forecast is for a chance of rain for most of the weekend with below normal temperatures.
Alfalfa is 18 to 24 inches tall with some Alfalfa weevil feeding, though not a serious problem. Potato leafhoppers arrived on May 22 in the Ida area. No first cutting yet as the weather is too unsettled and is forecast to remain so until after the Memorial Day holiday. The only cut hay I have seen has yet to harvest after about 10 days. This will be “brown” hay, harder to sell in our area where horse customers are finicky about hay color, though most do not test for quality.
Corn is growing slowly with many fields at V2, though the color has changed to all green. Most planting and replanting is finished, though some replanting “touching up” remains. Stands are variable in the low areas of some fields. No reports of slugs or cutworms and there are some weedy fields. Post spraying of corn has been hampered by windy conditions or rain. I expect corn to grow rapidly though will not be knee high by June 4.
Oats are a crop in demand for feed and straw. More acres were planted this spring and this crop looks good.
Soybeans are planted, emerged and growing slowly with most fields are at the V1 to V2 unifoliate leaf growth stage. Weeds are not an issue yet in most fields. I have not had any bean leaf beetle reports.
Wheat is mostly Feekes’ 10 and I expect flowering to occur over the holiday weekend, especially with more normal temperatures. I think the cold weather of early May hampered the growth in the low areas of some fields. Powdery mildew is present in susceptible varieties and I expect more disease pressure with the forecast for a chance of rain today, tomorrow, Saturday, Sunday and next Tuesday.
An Asian Soybean Rust and Aphid meeting and porkburger supper – with all the trimmings – will be held on Wednesday, June 1 at the 4-H Activity Center on the Monroe County fairgrounds. The supper begins at 6:00 PM courtesy of Bayer CropScience, Syngenta, Dow AgroScience and the Monroe County MSU Extension office. The meeting will run from 6:30 to 9:00 PM. Drs. Ray Hammerschmidt, Jeff Andresen, Chris DiFonzo of MSU; Dennis Clark of Bayer, Brick Goldman of Syngenta; Bart Marshall of Dow; Keith Reinholt of the Michigan Soybean Promotion Committee; and Ned Birkey of the Monroe County MSU Extension will be speaking. A twinjet nozzle will be demonstrated on a spray table and there will be several handouts on rust, aphids and spraying for rust. For directions or an agenda, call 734-240-3170.
Widespread rainfall over the past week has helped to bring soil moisture in the root zone back to favorable levels in most of southwest Michigan. We continue to remain well behind normal in terms of precipitation this spring, however, with rainfall deficits of two to three inches behind average from April 1 still prevalent. Cooler than normal temperatures, particularly at night, have kept the corn and soybeans from getting growth in high gear.
We have reached the 750 GDD41 threshold in most areas of the southwest region this week. Alfalfa plants may be just a little bit behind the normal growth rate for this milestone this year, which may have been caused by some of the late frosts. Alfalfa weevil larva feeding is above threshold in virtually all of the fields that I walked through that had not been treated already. If you have more than 40 percent tip feeding and are unable to harvest within the next week, you will probably want to apply an insecticide. The feeding damage that has occurred in many fields has been caused by high numbers of relatively small larvae, which means that there is plenty of potential for more damage to occur at a rapid pace as the insects grow. If you decide to treat your fields, be sure to look at the pre-harvest interval when selecting an insecticide to apply.
Planting is complete in commercial corn. Early-planted fields are at V2; later planted fields are at V1. Despite the fact that the early-planted corn has endured a good deal of less than ideal conditions, the plants seem to be doing fairly well. We simply need some warmer temperatures to get the crop moving. Black cutworm activity has been light. I have not seen much evidence if other insect problems at this point. Weed control is fairly good in most places. There are some weeds that have escaped pre-emergence treatments. Where grass weed seedlings have escaped, make sure that the species you have in your fields is not crabgrass, (See the weed control article in this issue by Kathrin Schirmacher). Growers have very limited options to control this weed has post emergence in non-herbicide resistant corn.
Seed corn planting is beginning to wind up. Most early-planted fields have both the male and female rows emerged at this point. Stands look good with no weed control problems. Some fields have been irrigated to help emergence and to activate herbicides.
The early-planted soybeans are setting their first trifoliate leaves. Many other fields have been planted recently and have not yet emerged or are in the crook stage. Spotty areas where intense rainfall occurred from thunderstorms are showing signs of crusting. Some producers are opting to put on a small amount of irrigation to reduce crusting and help the beans to emerge. I have seen very limited cutworm damage at this point.
Potatoes have emerged and are looking good. Slumping following the hilling operations may have exposed some fields to weed control issues, although fields look clean at this point.
Wheat is at flowering in the furthest south portion of the region. Drier conditions should help to reduce the potential for the development of Fusarium head scab. If wet conditions return over the holiday weekend, there is more potential for the disease to develop on fields where corn was raised last year. Powdery mildew can be seen in the lower canopy of many fields but the upper leaves are very clean this year. Wheat plant height and head size are reduce this year, presumably due to the dry conditions in April and early May. I have not seen signs of armyworms in wheat this year, but Eaton County Extension Educator George Silva had a grower report armyworm activity in a grass hay field in that county. It may be advisable to keep an eye on your wheat fields for this pest. Armyworm can reduce yield potential during grain fill if the flag leaf is threatened.
Approximately 0.1 to 0.5 inch of rain fell over much of the region this week. Temperatures have moderated somewhat though it is still rather cool with high temperatures in the 60s to low 70s. Low air temperatures have been in the 40s. Soil temperatures have improved with lows in the upper 40s to mid-50s.
Oat stands look generally good. Some fields are somewhat mixed in growth stages due to early dryness and slower emergence of some seedlings. Wheat is at Feekes stage 8 to 9 in the Montcalm area and Feekes 10 to 10.1 in Newago County. Few disease problems have been noted – powdery mildew is low in the canopy on susceptible varieties. Rye is heading.
Corn planting is essentially complete. Much of the crop has emerged and is in the VE to V1 growth stage. Corn is still generally pale in color and growing slowly.
Soybean planting is nearly complete. Emergence has been slow.
Alfalfa is 15 to 18 inches in height. Alfalfa weevil feeding is being observed and is below threshold at this time. Some harvesting of haylage is occurring where producers are short on feed. GDD41 totals as of May 24 are: Ionia 622, Entrican 525, Big Rapids 532 Fremont 587. For other totals go to:
http://www.agweather.geo.msu.edu/agwx/current/report.asp?fileid=base41gdd
The region received scattered showers over the past week. Some areas received as much as 0.7 of an inch while others received much less. For the most part there is adequate soil moisture at this time. The warmer days this week have really helped emerged crops grow rapidly.
The corn crop is emerged and in the 2-3 leaf stage or is just emerging. For the most part, the crop looks good at this time. Stands are generally good. The crop could use some heat. There are weed issues in many fields.
The soybean crop is planted and about one half of the crop has emerged. There are no problems at this time.
The wheat crop ranges from the boot stage down to Feeke’s 5-6. We have seen powdery mildew in several fields but it remains low in the plant. Continue scouting the crop for foliar diseases.
Oats and barley fields look very good. The stands are excellent. The cool weather has been near ideal for these crops. Many fields will need herbicide applications.
Sugar beets are progressing. There has been a little replanting because of poor stands. Weeds are a problem in some fields for some growers.
Alfalfa harvest has begun this week. Most fields in the southern part of the region are in the early bud stage while the north is about a week behind. We expect harvest to really get going next week. There has been no evidence of alfalfa weevil at this time. Scout fields for this pest. New seedings look very good.
Dry bean planting will begin next week.
Temperatures have been struggling to get into the 70s for most of the past week. This is causing somewhat slow crop development. Soil moisture is very good for germination and emergence of recently planted crops.
New growth continues to look good. Alfalfa is dealing with the cool temperatures nicely.
Sugar beets are progressing nicely with more leaves emerging from seedlings. Early fungicide applications for Rhizoctonia control are being planned for the next opportunity to get into the field.
The wheat crop has progressed to Feekes 8-9 with a good majority of flag leaves visible. Foliar diseases can be found but are mainly on lower leaves.
Stands of corn are looking pretty good. Emergence of most fields has been good with surface moisture helping to relieve soil crusting during critical times. Some fields have been replanted due to extended cold temperatures while others have had a combination of insect feeding, disease and soil crusting that has led to less than ideal populations.
Soybean planting is nearly finished with just a few fields to be planted. Emergence of early-planted fields looks good with a majority of this crop in the crook or cotyledon leaf stage.
A cooler, unsettled weather pattern is setting up across Michigan for the next several days, as an upper air low migrates slowly from northwest to southeast across the Great Lakes region. Cold air above the surface will result in a relatively unstable atmosphere and an almost daily chance for showers Thursday through Sunday (May 26-29).
During the day Thursday, a cool front will move from west to east across the state, setting off scattered showers and thunderstorms as it moves by. After the frontal passage, temperatures will fall back several degrees with a possibility of scattered showers (possibly including a rumble of thunder) each day Friday through Sunday. The showers are likely to be scattered in nature with limited areal coverage and amounts (in most cases, less than 0.25 inches where rain falls). Drier weather is likely once again on Memorial Day (Monday) and Tuesday of next week. Temperatures during the next several days will remain a few degrees below the climatological normals with highs ranging from the upper 50s north to the 60s south and lows generally in the 40s. High temperatures will slowly moderate back to the mid-upper 60s to low 70s by early next week.
In the medium range time frame, latest forecast guidance calls for a continuation of upper air troughing across the eastern United States and a broad ridging pattern across the western United States. However, the models are hinting at a pattern change about 8-10 days out with a trend towards west to east (zonal) flow across North America by the 8-14 day timeframe.
The NOAA Climate Prediction Center 6-10 day outlook (for May 31 through June 4) calls for temperatures and precipitation to remain at below normal levels. For the 8-14 day time frame (covering June 2-8), the official outlook calls for a return of near normal temperatures and precipitation totals statewide. However, due to quite a bit of uncertainty on the timing and ultimate configuration of the upper air pattern change mentioned above, forecaster confidence in the 8-14 day outlook is considered to be much less than normal.