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| Field Crop Advisory Team Alert newsletter | ||||
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| Vol. 22, No. 10, June 14, 2007 |
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In this issue  Check April-planted beans for soybean aphid now Western bean cutworm trapping starts Common pokeweed an emerging issue in Michigan crops Purple corn Yellow and red tipped flag leaves in wheat Potato disease extension bulletins Regional reports Weather |
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| Check April-planted beans for soybean aphid now As in 2005 Monroe County, this summer we have at least one area, in eastern Saginaw County, where soybean aphids are over threshold (view photos). The fields I saw were specifically near Frankenmuth. I did not see buckthorn in the immediate area, but this part of Saginaw County is downwind from the Shiawassee and Titibawassee Rivers, and a national game area south of Saginaw City, all with a lot of buckthorn. This situation appears to be unique – a combination of early planted beans plus a likely large flight of winged aphids from buckthorn in early May that settled in this area. On June 8, one particular V3 field was 100 percent infested, averaging 70 plus soybean aphid per plant. This field was planted in late April. By June 11, the field was over threshold, averaging 255 per plant. I recommended that this field be treated. When should small beans be sprayed? Heavy early-season infestations are rare, so research is lacking in this area. The 250 threshold was developed and tested in larger beans, so there is no good data to set a threshold for small beans. The infested fields I saw had adequate moisture to replace the aphid feeding (but in the last few days, they need rain), and the plants aren't putting on flowers or other critical structures. They appear to be able to tolerate 100 soybean aphid per plant, and maybe even 250. My lab, as well as researchers in Ontario, which has a similar situation, put out spray trials this week to try to answer this question. |
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| Be aware there are risks to spraying so early. Aphid populations are likely to rebound or “flare.” Predators will be killed, and any surviving aphids will reproduce fast in the absence of the predators. In early-sprays, insecticides can be mixed with Roundup from the crop-injury standpoint. However, it is critical to get excellent coverage to achieve excellent kill. Otherwise, you are leaving aphids alive to reproduce in the absence of predators. Some suggest using half-rates of insecticide because the plants are small. I do not have data to show that reduced rates are effective on small beans. Using half-rates makes me a bit nervous, because again, the goal is the excellent aphid kill to reset the field to “0” to avoid flaring. Because of the problem with flaring, early-sprayed fields may end up needing to be sprayed three times instead of once or twice to achieve the same yield. Spraying in Saginaw does not mean other fields in Michigan need to be treated. There is no cause for concern unless fields are 50-80 percent infested (in other words, the majority of plants have aphids). Once aphids spread out across plants, then numbers per plant begin to climb. If you are finding just a few infested plants in a field or a hot spot here and there, that is NOT a sprayable population. Aphids are present in most fields, but still at low levels, as in typical outbreak years. Aphids will spread out across plants and then numbers will climb as we head into July. The main point is to get out and look at the earliest planted fields to determine the percentage of infestation. Links to get insect trapping information: www.sbrusa.net - Aphid numbers in soybean. Currently Mchigan, Ohio, Indiana and Ontario have entered count data. http://www.ncpmc.org/traps/index.cfm: Northcentral Aphid Suction Trap Network. The web site now has 2007 trap catches. Simply click on the state or trap to see suction trap catches of soybean aphid. |
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| Western bean cutworm trapping starts
Trapping of western bean cutworm will begin at 20 locations in For more information, visit http://www.ent.iastate.edu/trap/westernbeancutworm/about: Western bean cutworm trapping – site will be active later in June. |
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| Common pokeweed an emerging issue in Michigan crops Over the last week common pokeweed plants have become more apparent in several Michigan fields. While common pokeweed is generally not a problem that most Michigan farmers think about, this weed has become increasingly prevalent throughout most of the state. In fact, in some cases common pokeweed infestations have reached populations that could interfere with crop yields. While there are no silver bullets to eradicate this weed from many fields, understanding the biology and conditions in which common pokeweed flourishes will ultimately help with management of common pokeweed. Common pokeweed biology Common pokeweed is a deep-rooted perennial that reproduces from root buds and seeds. Aboveground shoots of this plant arise from the taproot and consist of diffusely branched, fleshy stems (resembling a small tree) that can reach heights of 6 to 8 feet under fertile conditions (view photo1). In older plants, the taproot can be up to 6 inches in diameter and can grow to depths of more than 12 inches (view photo 2). Common pokeweed fruit is produced in late summer as clusters of green berries that turn purple to black at maturity and contain a profuse amount of red juice (view photo 3). The green leaves, fleshy stem, and purple berries of common pokeweed can inhibit the harvesting process and lead to discounts at the elevator for high seed moisture and staining. Areas with heavy infestations of common pokeweed can compete and reduce yield in both corn and soybeans. Numerous bird species are known to feed on the berries and are capable of randomly dispersing pokeweed seeds over sizeable areas. In fact, many times new common pokeweed plants are found at the base of trees or along electrical and telephone wires. Seedlings can emerge from mid-spring through early summer. Within five to nine weeks after emergence, seedlings of common pokeweed develop a taproot that is capable of regrowth (becomes perennial). New plants from dispersed seeds are capable of becoming entrenched as their taproots develop. Many plants that form taproots generally do not tolerate intensive tillage practices. Common pokeweed is generally not a problem in crop fields that are exposed to tillage. In fact, one of the most effective methods to control this weed is use of mechanical controls, such as moldboard plowing and disking. However, since reduced tillage has become a desirable practice for corn and soybean producers to help reduce soil erosion, decrease energy and crop production costs, and to save time during the planting season, alternative or chemical control methods are more desirable. Cultural control
Mechanical control
Several herbicides with residual activity are effective at controlling seedling common pokeweed. However, common pokeweed is more difficult to control once it has developed its taproot and becomes perennial. Because of the variable size of common pokeweed populations in a field, application timing is critical. For in-crop applications, time herbicide applications when common pokeweed is at least 8 inches tall and preferably less than 12 inches tall. Effectiveness ratings for several herbicides for common pokeweed control are available in the accompanying tables. Refer to the herbicide labels for maximum crop height and stage application restrictions for individual herbicides. Soybeans
Corn
Roundup Ready Crops
Noncrop/Fallow (Fall) c
b NIS = non-ionic surfactant; COC = crop oil concentrate; N = 28% UAN or AMS (ammonium sulfate). c Apply in late-September or early-October when common pokeweed is 8 to 24 inches tall, but before a frost. |
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| Purple corn There have been a number of reports of purple-colored corn seedlings this year. These symptoms are not unusual for Michigan, but have been particularly prevalent this year. There are several factors that contribute to the purple color, but the main culprit is likely restricted root growth. The April rains and early season planting delays may have caused some growers to “jump the gun” and begin planting before field moisture conditions were optimal. Restricted root growth resulting from compacted soil and smeared and compacted seed furrow side-walls can contribute to the buildup of sugars in the corn leaf. The abundant sunshine and accumulation of heat units the past week have resulted in the production of lots of sugars in the corn plant shoots. These sugars would normally be used for root and shoot growth, but when accumulated in the leaf, result in the production of anthocyanins, which give the leaf a purple color. If the purple color persists after field conditions normalize, the discoloring may be indicative of other root-related problems such as a severe compaction problem or phosphorus deficiency in the soil. In addition, some corn varieties are genetically predisposed to have inherently higher levels of anthocyanins. These varietal differences are readily apparent when viewing variety trial plots this time of year, however, they do not appear to affect final grain yield. Growers in the sugar beet producing areas of the state often report an increased incidence of purple-colored corn following sugar beet. This phenomenon was investigated by Don Christenson at MSU in the mid 1990’s. The work did not find a correlation with sugar beet carry-over herbicides, soil P levels and did not appear to be an artifact of soil compaction. The results indicate there may be an association with the sugar beet residue and early season purpling of rotational corn. Nevertheless, the increased incidence and severity of purpling following sugar beet was not detrimental to corn yield. The good news is that corn will generally overcome early season purpling. Continue to monitor nutrient levels, particularly nitrogen and identify severely compacted areas for remedial tillage in the fall. Above all, next year use patience and discretion in deciding when to resume field planting operations following rainfall. |
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| Yellow and red tipped flag leaves in wheat There have been a couple of reports in Michigan of wheat with a red or yellow discoloration beginning at the flag leaf tip and progressing toward the base of the leaf. There is no stunting of the heads and minimal stunting of the plants. These leaf discoloration symptoms, along with stunted heads, stunted plants and flag leaves remaining in an upright position, are classic symptoms of barley yellow dwarf virus, an aphid transmitted virus. Greg Shaner, professor of plant pathology at Purdue University, reported that barley yellow dwarf virus was the most significant disease problem of wheat in Indiana this year. Most of the reports of suspected barley yellow dwarf virus in Michigan have come from counties located along the Indiana border, however, one of our research sites in East Lansing shows the same symptoms (see photos). Barley yellow dwarf virus has not yet been confirmed from these suspect fields, but samples are being collected for virus testing, and we’ll report the results in the Field Crop CAT Alert. Environmental stresses and nutritional disorders can cause similar symptoms. Barley yellow dwarf virus is transmitted by several different species of aphids, including oat bird-cherry, corn leaf and English grain aphids. The virus persists in volunteer grains or wild grasses. It is reintroduced to crops each year, sometimes from aphids that have migrated from great distances away on storms. The disease usually occurs in small patches or portions of rows, sometimes along field margins. Symptoms are most severe when infection takes place in the fall, less so when infection occurs in the spring. When temperatures are around 68°F, virus symptoms are visible in about two weeks. As temperatures warm, symptom expression takes longer, for example, four weeks at 77°F. No symptom expression occurs at 86°F. Yield losses to barley yellow dwarf virus depend on the growth stage at the time of infection, cool weather conditions that favor disease development and the susceptibility of the variety. There is little that can be done to save diseased plants and management should focus on preventing the disease. There are resistant oat varieties, but wheat has limited resistance to barley yellow dwarf virus. Check with your seed dealer for recommendations about resistant varieties. Avoid early planting to avoid exposure to aphids during early crop growth stages. Control volunteer wheat barley, oats and wild grasses. Although foliar insecticides are available to control aphids, their short residual life gives them limited usefulness in barley yellow dwarf virus management. |
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| Potato disease extension bulletins Seven new high resolution potato diseases extension bulletins are now available for purchase at http://www.emdc.msue.msu.edu/ for $1.50 each. The new group of publications includes the recent potato late blight bulletin and bulletins on early blight, pink rot, Fusarium dry rot, Rhizoctonia diseases, potato common scab, white mold and seed piece management. For more information, call 517-353-6740. You can also download these bulletins from this web page http://www.potatodiseases.org/extensionpubs.html as PDF files from our late blight website. Also at http://lateblight.org daily updates of potato late blight risk are available for all the Michigan Automated Weather Network sites in Michigan and updates on extension meetings being held throughout the state. |
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| Regional reports 1 -- Southeast Ned Birkey Weather Weather has turned hot and dry with no rain and none in the immediate forecast. Crop reports Alfalfa was cut with the favorable weather this past week. This should finish the alfalfa weevil feeding. Although hay was past prime quality, at least most fields did not get rained upon. Corn is at the V8 growth stage with some fields showing drought stress. Fall soil compaction is clearly showing up on end rows and elsewhere in fields with highly variable corn height. Fields with good drainage and good stands are evident as are fields with compaction, drainage or stand problems. Now is a good time to evaluate planter performance. Sidedressing is finishing up and weed control is still an issue in some fields. European corn borer counts were down in all trap locations this week. Fireflies are out so corn rootworms should be also. Soybeans are starting to take root and show more top growth. Most fields are at the V2 growth stage. Bean leaf beetle feeding continues, though no soybean aphids were found at the Lenawee location this week. Soybean aphid and rust plots will become established in Monroe and Washtenaw counties next week. Western bean cutworm and corn rootworm traps will also go up next week. Post weed control will soon become the main farm chore. Wheat has finished flowering and is now at Feekes’ growth stage 11. The continued high temperatures near 90ºF will hasten ripening. I am cautiously optimistic about wheat yields. Miscellaneous The MSU Wheat Variety Trial location for southeast Michigan is at Dave and Jason Woods’ farm and is located on Bucholtz Highway, south of Holloway Road, north of Deerfield and south of Britton. The plot is signed for farmers and others to view the 67 different soft white and red varieties. |
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| 2 -- Southwest Bruce MacKellar Weather There has been no rainfall over the week. Hot weather with daytime highs in the upper 80’s and nighttime temperatures in the upper 60’s to lower 70’s have really pushed the crop development into high gear this last week. In fact, the Kalamazoo area is running about 150 base 50 growing degree day units ahead of the 30-year average for southwest Michigan. To put this in perspective, this is the equivalent of between seven and eight 85 degree days ahead of the norm, and 12-13 ahead of where we were at this point in the growing season last year. As a result, many of the crops, weeds and insects are well ahead in their growth curves compared to the norm. Crop reports Commercial corn is the crop that continues to take advantage of the warm conditions. Early planted corn is approaching waist high V9 to V10 with later planted corn mostly in the V5-V6 range. Side-dress nitrogen applications are completed on the earlier planted fields and continue to be applied rapidly on later planted fields. The average evapotranspiration rate for the largest corn is between 0.1 and 0.12 inches per day at this point. Early development begins early in corn, around the 6 leaf collar stage. Between V6 and V12, many of the factors that determine the ear size, and kernal counts are being determined. By V12, corn is beginning to become more susceptible to yield losses from drought and other stresses. Severe stresses can impact yields by 10 percent or so at this stage. European corn borer moth activity appears to be on the decline. You can find the telltale marks on corn leaves that denote some early instar European corn borer feeding on corn plants has begun, but the number of plants that show damage appears to be minimal at this time. We anticipate that rootworm larval feeding will be on the rise as the eggs should have hatched over the last week or so. With the deposition of armyworm moths into portions of west Michigan from the storms that crossed the area last weekend, we will have to monitor corn fields for potential effects of larval feeding over the next couple of weeks. Seed corn planting is nearly complete. There has been a long planting window this year. Early planted seed corn continues to look good. There continues to be some fields where weed escapes can be found in seed corn, but most are being treated with post emergence applications and are improving. Irrigation has been applied to many of the later planted fields to improve conditions for germination and emergence. As with the commercial corn, we need to monitor fields for armyworm larval feeding because of the step up in moth deposition over the last week. Early planted soybeans are developing their third to fourth tri-foliate. Bean leaf beetle feeding signs remain low. Herbicide application has been completed in many of the earlier planted beans, with those planted in mid-May receiving post applications at this time. There continue to be low numbers of soybean aphids in fields at this time. The treatment threshold is 250 aphids per plant, perhaps less on small, later planted fields. We will likely begin to see pockets where aphid numbers will begin to increase in numbers in southwest Michigan. It will be increasingly important to monitor aphid numbers in the area, particularly if the dry conditions persist. Alfalfa harvest moved into high gear here this week, as the first really good extended forecast that has shown an extended dry period. Potato leafhoppers are prevalent. Watch your alfalfa re-growth carefully for this pest, because the early re-growth period is the most vulnerable to “hopper burn” injury. It does not take many leafhoppers to cause serious injury on 2-3 inch alfalfa. While the temperatures have driven the grain filling period at a fast pace, wheat will probably have good yield potential in the region, especially where irrigation was used to provide supplemental water when needed. It appears that the number of heads affected by fusarium head blight will be limited this year despite some extended wet periods during flowering. Meetings The St. Joseph County IPM Breakfast Meeting will be held on Wednesday, June 20, at the St. Joseph County MSU Extension office, 7:00 AM-9:00 AM . Cost is $7, which includes a catered in breakfast. Our guest speaker next week will be Dr. Chris DiFonzo. |
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| 3 -- West Central Fred Springborn Weather Warm and dry sums up the weather of the past week with perhaps an emphasis on dry. Irrigation systems are running across much of the county. High temperatures in the last week have ranged from the lower 80’s to the lower 90’s. Crop reports Wheat is well past flowering in all fields. A few fields have shown some symptoms of glume blotch. Oats are progressing well with few insect or disease problems at this time. Corn growth ranges from V3 to V10. The majority are in the range of V5 to V8. We are still getting complaints of yellow, red and purple corn. Much of this is related to weather and some is due to other factors. European corn borer trap catches are down a bit this week with an average of five moths per trap at our Stanton and Trufant trap sites. Soybean planting is virtually complete with most fields ranging from V1 to V4. Dry bean planting is in full swing with 60 percent of the crop planted. Earlier planted beans have emerged. Alfalfa harvest is underway with nearly 75 percent of the crop harvested. Quality is going down rapidly with over ripe grasses. On the plus side, there is rapid drying and short cut to bale time. Potato leafhopper is active with both adults and nymphs present. In Newaygo County, every hay machine in the area is either working or broken down. One local equipment parts man was quoted "one more haybine customer and I'll freakout." Volunteer potatoes continue to be an issue. |
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| 4 -- Central Paul Gross Weather The crops enjoyed the warm temperatures over the past week and responded with rapid growth. Crops are living off the rains of last week and will need a rain in the next week to continue to progress normally. It is evident where there were harvest problems last fall or where crops were planted in wet conditions, stands are variable and are showing drought stress in some areas of the fields. Generally crops are off to a good start this year. Crop reports The corn crop is growing rapidly with the warm weather. Stands are variable. Fields that are well drained and were planted when conditions were right are excellent. We are seeing some purple corn, but expect the crop to grow out of that condition. Field activities include herbicide and nitrogen applications. Rain would be welcomed. The soybean crop is progressing normally. We have found soybean aphid in each of the central region counties, but in very low numbers. Fields should be scouted regularly for this pest as the population can explode virtually over night. Field activities include herbicide applications. The wheat crop is done flowering, and the yield potential looks good. We are seeing the normal foliar diseases, but nothing serious at this time. The big question is will we have head scab as much of our wheat flowered during the two to three day wet period two weeks ago. Scout fields for armyworm as this pest usually shows up this time of year. Alfalfa harvest should wrap up this week. The weather has been great for making hay. Yields vary with some reporting below average, while others report excellent yields. It appears that first cutting yields may be correlated with the fall harvest schedule. We are seeing leafhoppers at levels that need to be monitored. The oat crop is heading and looks very good. Sugarbeets are dong very well with some fields beginning to fill the row. Drybean planting will wrap up this week. Early planted fields have emerged. Scout new growth for leafhoppers. |
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| 5 -- Thumb Mark Seamon Weather Warm and dry describe most of the past week throughout the Thumb area. This has helped to dry out the southern Thumb, but others areas are getting a little too dry. Alfalfa to be baled has made good progress with first cutting this week. Sugar beets continue to look good in most areas. Variable fields are improving but slowly. The most advanced fields in 28 or 30 inch rows are approaching row closure. The wheat crop is beyond flowering. These high temperatures and dry soil conditions may reduce the grain fill period and affect yield potential. Corn growth is active with the tallest corn about 24 inches tall and in the V6 growth stage. Sidedress nitrogen applications are being wrapped up in many areas. Leafrolling can be seen in many fields, especially fields with compaction from last fall or heavy rain this spring. Most soybean fields have emerged with the most advanced fields at the V4 growth stage. Soybean aphids have arrived with varying populations from none to over 250 per plant. Bean leaf beetle feeding is easy to find. Cruiser seed treatment has been effective in control of the bean leaf beetles. Farmers have made great progress planting over the past week with more than 90 percent of this crop planted. Emergence has been good. |
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| Weather news Jeff Andresen Agricultural Meteorology Geography A strong upper air ridge and associated surface high pressure across the central United States will persist for a couple more days, with fair, warm and dry weather expected to continue across much of the region. A weak cool front will move into Michigan from the north on Saturday, but given very limited moisture ahead of it, only a few scattered showers and thundershowers are expected (mainly in northern sections of the state). Otherwise, dry conditions are a good bet across most locations through this Sunday, especially across southern sections of the state. Temperatures through Sunday will remain at above normal levels, with highs ranging from the upper 70's in northern lakeshore areas to the upper 80's south and lows falling into the mid 50's north to mid 60's south. An upper air trough and associated cool front are expected to move into the region by the middle of next week, which will likely be the next chance for significant/widespread precipitation. Time-wise, this weather feature should bring the chance for showers and thunderstorms in western sections of the state by Monday evening and across the east on Tuesday. Following the movement of the troughing feature through the region next week, current medium range forecast guidance for the 6-10 day and 8-14 day time frames covering June 19-23 and June 21-27 respectively, suggests that the troughing pattern mentioned above will linger for much of the latter part of next week, resulting in a cooler and more unsettled weather pattern. Above normal precipitation totals are forecast for both time frames. Temperatures during the 6‑10 day period are forecast to remain at near normal levels, which during the 8-14 day period, temperatures are forecast to range from near normal in northeastern sections of the state to below normal in the southwest. |
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